@article{zhang_pugliano_cao_kim_annam_popy_pinky_yang_garg_borunda_et al._2023, title={Crystal growth, structural and electronic characterizations of zero-dimensional metal halide (TEP)InBr<sub>4</sub> single crystals for X-ray detection}, volume={11}, ISSN={["2050-7534"]}, DOI={10.1039/d3tc02787b}, abstractNote={A new 0D metal halide (TEP)InBr4 is reported. Structural and electronic properties were studied. The fabricated X-ray detector using a (TEP)InBr4 single crystal showed a detection sensitivity of 569.85 μC Gy−1 cm−2 at E = 100 V mm−1.}, number={43}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, author={Zhang, Zheng and Pugliano, Tony M. and Cao, Da and Kim, Doup and Annam, Roshan S. and Popy, Dilruba A. and Pinky, Tamanna and Yang, Ge and Garg, Jivtesh and Borunda, Mario F. and et al.}, year={2023}, month={Nov}, pages={15357–15365} }
 @article{basirico_yang_sellin_2023, title={Editorial: Perovskite and organic materials for radiation detectors}, volume={11}, ISSN={["2296-424X"]}, DOI={10.3389/fphy.2023.1242329}, abstractNote={EDITORIAL article Front. Phys., 05 July 2023Sec. Radiation Detectors and Imaging Volume 11 - 2023 | https://doi.org/10.3389/fphy.2023.1242329}, journal={FRONTIERS IN PHYSICS}, author={Basirico, Laura and Yang, Ge and Sellin, Paul}, year={2023}, month={Jul} }
 @article{alshogeathri_cao_kim_yang_2023, title={Gel growth and characterization of Cs3Bi2Br9 perovskite single crystals for radiation detection}, volume={11}, ISSN={2296-424X}, url={http://dx.doi.org/10.3389/fphy.2023.1129301}, DOI={10.3389/fphy.2023.1129301}, abstractNote={Metal halide perovskites have been sought for ionizing radiation detection due to their tunable bandgap, high quantum yield, high absorption coefficient, excellent charge transport properties, flexible chemistry synthesis and cost-effective manufacturing. Among the family of perovskites, bismuth-based halide perovskites have attracted a rapidly growing interest as possible alternatives to lead-based halide perovskites in the development of nontoxic perovskites for opto-electronic devices. Herein, bismuth-based inorganic perovskite Cs3Bi2Br9 single crystals were successfully grown using an innovative dual-diffusion gel growth technique for the first time. Silica gel has been developed as an enabling medium for gel growth of single crystals due to its transparency and easy control of nucleation sites. The UV-vis transmission spectrum was recorded using a light source of deuterium and halogen lamps and a Tauc plot was obtained, which gave an estimate of the bandgap energy, 2.54 eV. Silver electrodes were used on the top surface and the bottom surface of Cs3Bi2Br9 single crystals for material characterization and detector tests. Current-voltage (I-V) measurements gave a room-temperature resistivity of 1.79×1011 Ω•cm. The Cs3Bi2Br9 single crystals were then tested for X-ray response using ON\OFF testing which revealed attractive responsiveness for X-ray photons (rise and fall time: ≈0.3 s ). Using the net current (IXray−Idark), which can be extracted from the X-ray response measurements at varied applied voltages, a modified Hecht fitting was applied to estimate the mobility-lifetime product of electrons, μτ=5.12×10−4 ±6.70×10−5 cm2/V for a Ag/Cs3Bi2Br9/Ag device. This study shows that our innovative crystal growth method, enabled by the unique gel growth process, can be used as an appealing technique to grow functional crystals for opto-electronic devices. Meanwhile, Cs3Bi2Br9 has shown great potential as a promising candidate for X-ray detection applications. The efforts in this work will serve as a metric for growing halide perovskites in the gel for opto-electronic devices.}, journal={Frontiers in Physics}, publisher={Frontiers Media SA}, author={Alshogeathri, Saqr and Cao, Da and Kim, Doup and Yang, Ge}, year={2023}, month={Mar} }
 @article{cao_yang_2022, title={Effect of low-temperature annealing on Bi-poor Cs2AgBiBr6 single crystals}, volume={33}, ISSN={["2352-4928"]}, url={http://dx.doi.org/10.1016/j.mtcomm.2022.104242}, DOI={10.1016/j.mtcomm.2022.104242}, abstractNote={All-inorganic double perovskite Cs 2 AgBiBr 6 has attracted increasing research interest due to its great potential for optoelectronic applications. To date, most studies focus on the room-temperature characteristics of as-grown Cs 2 AgBiBr 6 single crystals. In this work, we investigated the effect of low-temperature annealing on the physical properties of Cs 2 AgBiBr 6 single crystals. The studied Cs 2 AgBiBr 6 single crystal was grown using a Bi-poor precursor and has a bandgap of 2.12 eV, showing superior elastic properties with Young’s modulus at 32 GPa and hardness at 1 GPa. When the annealing temperature increased from 25 °C to 80 °C, the resistivity of the as-fabricated Bi-poor Cs 2 AgBiBr 6 crystal decreased from 8.07×10 9 Ω cm to 5.86×10 7 Ω cm. Interestingly, the room-temperature resistivity of the annealed Cs 2 AgBiBr 6 increased nearly 3 times when compared to the original value before the annealing. After the annealing, the Cs 2 AgBiBr 6 crystal still holds a strong response to radiation sources. The temporal response of the Cs 2 AgBiBr 6 crystal under the 568-nm LED illumination also indicated that the rising time and the decay time are much shorter than the initial values before the annealing. These results demonstrate a robust thermal and air stability of Bi-poor Cs 2 AgBiBr 6 single crystal. An effective annealing strategy could play an important role in tuning the fast decay- and rise-time characteristics of Cs 2 AgBiBr 6 single crystals. • Fabricated Bi-poor Cs 2 AgBiBr 6 single crystals and studied the effect of low-temperature annealing on it. • The resistivity increased nearly 3 times after the annealing temperature up to 80 °C. • The fabricated device showed a strong response to gamma sources and LED illumination of 568 nm before and after annealing. • The response time to LED illumination enhanced a lot after low-temperature annealing.}, journal={MATERIALS TODAY COMMUNICATIONS}, publisher={Elsevier BV}, author={Cao, Da and Yang, Ge}, year={2022}, month={Dec} }
 @article{kim_yang_2022, title={Perovskite materials: from single crystals to radiation detection}, ISSN={["1466-8033"]}, DOI={10.1039/d2ce00637e}, abstractNote={Pb- and Bi-based perovskite materials have high potential for detecting ionizing radiation but an enhanced research effort is needed to achieve large-size, high-performance single crystals at a competitive cost to accelerate this development.}, journal={CRYSTENGCOMM}, author={Kim, Doup and Yang, Ge}, year={2022}, month={Jun} }
 @article{kanies_hayes_yang_2022, title={Thermoluminescence and optically stimulated luminescence response of Al2O3 coatings deposited by mist-chemical vapor deposition}, volume={191}, ISSN={0969-806X}, url={http://dx.doi.org/10.1016/j.radphyschem.2021.109860}, DOI={10.1016/j.radphyschem.2021.109860}, abstractNote={Aluminum oxide (Al2O3) is a widely used ceramic material which can be applied as a protective coating on metallic structures to improve corrosion resistance and mechanical properties. Al2O3 also has great potential as a functional thin film device in optoelectronics. When it is doped with carbon (Al2O3:C), this material system can serve as a reliable radiation dosimeter. The combination of optoelectronic, dosimetric, and protective properties demonstrated by Al2O3 uniquely positions it for dual use applications in nuclear forensics, nonproliferation and safeguards, emergency response, retrospective dosimetry, and nondestructive inspection. In this study, an innovative ultrasonic mist-chemical vapor deposition (Mist-CVD) system was used to deposit thin (nm level) Al2O3 coatings on 304 stainless steel substrates. The single aliquot regeneration (SAR) and additive dose reconstruction techniques were then used to investigate the thermoluminescence (TL) and optically stimulated luminescence (OSL) response of the coated substrates to increasing doses of β irradiation. This study demonstrates that nm-thick Al2O3 coatings hold promise as novel nano-dosimeters which could be leveraged for a series of applications such as nonproliferation and safeguards, retrospective dosimetry, and nondestructive inspection.}, journal={Radiation Physics and Chemistry}, publisher={Elsevier BV}, author={Kanies, Bryant and Hayes, Robert and Yang, Ge}, year={2022}, month={Feb}, pages={109860} }
 @article{zhang_cao_huang_danilov_chung_sun_yang_2021, title={Gamma-Ray Detection Using Bi-Poor Cs2AgBiBr6 Double Perovskite Single Crystals}, volume={9}, ISSN={["2195-1071"]}, url={https://doi.org/10.1002/adom.202001575}, DOI={10.1002/adom.202001575}, abstractNote={Abstract}, number={8}, journal={ADVANCED OPTICAL MATERIALS}, publisher={Wiley}, author={Zhang, Zheng and Cao, Da and Huang, Zhengjie and Danilov, Evgeny O. and Chung, Ching-Chang and Sun, Dali and Yang, Ge}, year={2021}, month={Apr} }
 @article{roy_camarda_cui_yang_james_2021, title={Impact of selenium addition to the cadmium-zinc-telluride matrix for producing high energy resolution X-and gamma-ray detectors}, volume={11}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-021-89795-z}, abstractNote={Abstract}, number={1}, journal={SCIENTIFIC REPORTS}, author={Roy, Utpal N. and Camarda, Giuseppe S. and Cui, Yonggang and Yang, Ge and James, Ralph B.}, year={2021}, month={May} }
 @misc{blevins_yang_2021, title={On optical properties and scintillation performance of emerging Ga2O3: Crystal growth, emission mechanisms and doping strategies}, volume={144}, ISSN={["1873-4227"]}, DOI={10.1016/j.materresbull.2021.111494}, abstractNote={As an emerging ultra-wide bandgap compound semiconductor, Ga2O3 has attracted rapidly growing interest due to its unique physical properties for harsh condition applications. Compared to Ga2O3’s electrical-characteristic based uses, such as power electronics, photodetectors and solar cells, a much less explored area for Ga2O3 is its promising optical properties and its related scintillation capabilities. Undoped Ga2O3 is a strong scintillator with excellent scintillation characteristics such as fast decay constants and encouraging light yield which is comparable to that of the classic Bi4Ge3O12 (BGO) scintillator. The scintillation capability of Ga2O3 can be precisely tuned via a series of approaches including systematic crystal growth control, post-growth annealing, targeted doping, and optimization of operation temperature. Here we summarize exciting progress of Ga2O3 scintillators which have been pursued over the past few years. Our efforts cover a series of growth techniques of Ga2O3 materials as well as discussion of emission mechanisms. Furthermore we dedicate a targeted portion toward the doping strategies to improve the performance of Ga2O3. A detailed analysis is provided to compare the impact of different dopants. Through these efforts, we hope to provide useful perspectives to help accelerate the development of high performance Ga2O3 scintillators.}, journal={MATERIALS RESEARCH BULLETIN}, author={Blevins, Jacob and Yang, Ge}, year={2021}, month={Dec} }
 @misc{zhang_yang_2021, title={Recent advancements in using perovskite single crystals for gamma-ray detection}, volume={32}, ISSN={["1573-482X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85085091410&partnerID=MN8TOARS}, DOI={10.1007/s10854-020-03519-z}, number={10}, journal={JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS}, author={Zhang, Zheng and Yang, Ge}, year={2021}, month={May}, pages={12758–12770} }
 @article{blevins_yang_2020, title={Enabling Ga2O3's neutron detection capability with boron doping and conversion layer}, volume={128}, ISSN={["1089-7550"]}, DOI={10.1063/5.0015522}, abstractNote={There is a growing necessity to develop revolutionary neutron detectors for nuclear energy, nuclear physics, medical physics, astrophysics, biological imaging, nonproliferation, and national security. The often-used Helium-3 (He-3) neutron detector is becoming increasingly difficult to obtain due to He-3 shortages. As an emerging oxide semiconductor material, Ga2O3 exhibits excellent physical properties. These physical merits enable Ga2O3’s potential as a high-performance semiconductor neutron detector for extreme condition applications. Here, two approaches are explored, i.e., applying an exterior conversion layer of boron-10 (B-10) on Ga2O3 and directly doping B-10 into Ga2O3 to demonstrate Ga2O3’s capability for neutron detection. Using Monte Carlo simulation, we show the distinct difference in neutron detection efficiency of Ga2O3 when applying direct doping of B-10 into Ga2O3 vs applying a uniform B-10 conversion layer on top of Ga2O3. Our results exhibit that the theoretically predicted maximum doping level of B-10 in Ga2O3 does not lead to the same detection efficiency as that of a simple B-10 conversion layer when detecting 480 keV gammas. Except for the most thermalized neutrons at 0.01 eV, direct doping simulations are not able to achieve comparable results to that of the conversion layer method.}, number={15}, journal={JOURNAL OF APPLIED PHYSICS}, author={Blevins, Jacob and Yang, Ge}, year={2020}, month={Oct} }
 @article{hany_yang_chung_2020, title={Fast X-ray detectors based on bulk beta-Ga2O3 (Fe)}, volume={55}, ISSN={["1573-4803"]}, url={https://doi.org/10.1007/s10853-020-04665-9}, DOI={10.1007/s10853-020-04665-9}, number={22}, journal={JOURNAL OF MATERIALS SCIENCE}, publisher={Springer Science and Business Media LLC}, author={Hany, Ibrahim and Yang, Ge and Chung, Ching-Chang}, year={2020}, month={Aug}, pages={9461–9469} }
 @article{cao_yang_bourham_moneghan_2020, title={Gamma radiation shielding properties of poly (methyl methacrylate) / Bi2O3 composites}, volume={52}, ISSN={["1738-5733"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85085064327&partnerID=MN8TOARS}, DOI={10.1016/j.net.2020.04.026}, abstractNote={This work investigated the gamma-ray shielding performance, and the physical and mechanical properties of poly (methyl methacrylate) (PMMA) composites embedded with 0–44.0 wt% bismuth trioxide (Bi2O3) fabricated by the fast ultraviolet (UV) curing method. The results showed that the addition of Bi2O3 had significantly improved the gamma shielding ability of PMMA composites. Mass attenuation coefficient and half-value layer were examined using five gamma sources (Cs-137, Ba-133, Cd-109, Co-57, and Co-60). The high loading of Bi2O3 in the PMMA samples improved the micro-hardness to nearly seven times that of the pure PMMA. With these enhancements, it was demonstrated that PMMA/Bi2O3 composites are promising gamma shielding materials. Furthermore, the fast UV curing exerts its great potential in significantly shortening the production cycle of shielding material to enable rapid manufacturing.}, number={11}, journal={NUCLEAR ENGINEERING AND TECHNOLOGY}, author={Cao, Da and Yang, Ge and Bourham, Mohamed and Moneghan, Dan}, year={2020}, month={Nov}, pages={2613–2619} }
 @article{blevins_yang_2020, title={Machine learning enabled advanced manufacturing in nuclear engineering applications}, volume={367}, ISSN={["1872-759X"]}, DOI={10.1016/j.nucengdes.2020.110817}, abstractNote={Advanced manufacturing has gained tremendous interest in both research and industry in the past few years. Over nearly the same period of time, machine learning (ML) has made phenomenal advancements, finding its way into many aspects of manufacturing. For the nuclear engineering field, the adoption of advanced manufacturing is a compelling argument due to the ambitious challenges the field faces. The combination of advanced manufacturing with ML holds great potential in the nuclear engineering field, and even further development is needed to accelerate their deployment towards real-world applications. This review paper seeks to detail several key aspects of ML enabled advanced manufacturing that are used or could prove useful to nuclear applications ranging from radiation detector materials to reactor parts fabrication. The applications covered here include new material extrapolation, manufacturing defect detection, and additive manufacturing parameters’ optimization.}, journal={NUCLEAR ENGINEERING AND DESIGN}, author={Blevins, Jacob and Yang, Ge}, year={2020}, month={Oct} }
 @article{yang_phan_liu_hawari_kim_2020, title={Material defect study of thallium lead iodide (TlPbI3) crystals for radiation detector applications}, volume={954}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2018.10.194}, DOI={10.1016/j.nima.2018.10.194}, abstractNote={TlPbI3 is a promising semiconductor material for fabricating room-temperature radiation detectors, which have wide applications in national security, medical imaging, astrophysics research, industrial process monitoring and environmental survey. TlPbI3 has a large energy bandgap at 2.3 eV, a high density (6.04 g/cm3) and high concentrations of the high atomic number elements Tl and Pb. Such physical properties offer great potential to use TlPbI3 to detect gamma-ray at room temperature with high detection efficiency. In this work, we used the positron annihilation lifetime spectroscopy (PALS) measurement and infrared transmission microscopy to study the material defects in bulk TlPbI3 crystals. These crystals were grown with Bridgman method. For the PALS measurements, we used the positron experimental setup at North Carolina State University’s PULSTAR reactor facility. A 15 μCi Na-22 positron source sealed with 7.6μm thick Kapton films was sandwiched between two identical pieces of TlPbI3 samples. Two cylindrical plastic scintillators (1 inch diameter by 1 inch long) combined with Hamamatsu H3378-50 photomultiplier tubes (PMT) were used to detect the 1.27 MeV gamma-rays in coincidence with the 511 keV annihilation gamma-rays as the start and the stop signals, respectively. A LeCroy Wavepro 7300A digital oscilloscope was used to digitize the raw PMT pulses and acquire the PALS spectra. The dominating positron lifetime in TlPbI3 is 393 ps and its intensity is more than 92%. This component is typically attributed to some vacancy type (or more likely, vacancy cluster) positron trapping sites. The first component of ∼ 140 ps could be related to mono-vacancies or positrons annihilate in a delocalized lattice state. Compared with MAPbI3, the higher average lifetime, τav, and the higher intermediate lifetime (τ2) in TlPbI3 indicate the presence of more anion-type vacancies and imply an increase in ionic conductivity. Using infrared transmission microscopy, we also observed the formation of large volume TlPbI3 single crystal even in the transition portion between the conical seeding pocket and the normal growth chunk.}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Yang, G. and Phan, Q.V. and Liu, M. and Hawari, A. and Kim, H.}, year={2020}, month={Feb}, pages={161516} }
 @article{cao_yang_2020, title={Quantum dot/polymer nanocomposite monolith for radiation detection}, volume={24}, ISSN={["2352-4928"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85085179655&partnerID=MN8TOARS}, DOI={10.1016/j.mtcomm.2020.101246}, abstractNote={Plastic scintillators have received strong interest as an important type of radiation sensing material due to their relatively high light output, fast decay time, low fabrication cost, excellent durability, and most importantly, the capability to be shaped into desired forms through the use of molds or other approaches. However, the interior sensitivity and energy resolution of traditional plastic scintillators limit their competitiveness when compared with their inorganic counterparts. The doping of quantum dots (QDs) with high-Z element into plastic scintillators has recently been demonstrated as an effective way to improve gamma stopping power and scintillation efficiency. In this regard, a series of research activities have been conducted to address the aggregation and self-absorption problem of QDs to achieve high-performance transparent plastic scintillators with a high concentration of QDs load. Here we present a comprehensive review to offer a timely reference source to accelerate the development of this exciting research area. This review covers the description of basic theory, the summary of recent experimental progress, and the discussion of future trends of QD-doped nanocomposite plastic scintillators.}, journal={MATERIALS TODAY COMMUNICATIONS}, author={Cao, Da and Yang, Ge}, year={2020}, month={Sep} }
 @article{wu_yang_han_liu_hawari_du_peng_foster_chen_koschan_et al._2020, title={Role of Lithium Codoping in Enhancing the Scintillation Yield of Aluminate Garnets}, volume={13}, ISSN={["2331-7019"]}, DOI={10.1103/PhysRevApplied.13.064060}, abstractNote={The aim of this work is to clarify the scintillation-yield enhancement in $\mathrm{Lu}\mathrm{YAG}:\mathrm{Pr}$ scintillators obtained by $\mathrm{Li}$ codoping via integrated study of the valence state of activators, the preferential site occupancy of $\mathrm{Li}$ codopants, and defect structures from experimental and theoretical insights. With $\mathrm{Li}$ codoping, the light yield and energy resolution of $10\ifmmode\times\else\texttimes\fi{}10\ifmmode\times\else\texttimes\fi{}10\phantom{\rule{0.1em}{0ex}}{\mathrm{mm}}^{3}$ $\mathrm{Lu}\mathrm{YAG}:\mathrm{Pr}$ samples are improved from 15 600 to 24 800 photons/MeV, and 5.3 to 4.3% at 662 keV, respectively. The optical absorption spectra indicate that $\mathrm{Li}$ codoping does not induce conversion of stable ${\mathrm{Pr}}^{3+}$ to ${\mathrm{Pr}}^{4+}$ in $\mathrm{Lu}\mathrm{YAG}:\mathrm{Pr}$ single crystals. Based on the formation energies of substitutional and interstitial $\mathrm{Li}$ sites using density-functional-theory (DFT) calculations and the ${}^{7}\mathrm{Li}$ nuclear magnetic resonance results, it is shown that the $\mathrm{Li}$ ions prefer to dominantly occupy the fourfold coordinated interstitial sites and fourfold coordinated $\mathrm{Al}$ sites. The systematic analysis of thermoluminescence glow curves, positron annihilation lifetime spectroscopies, and defect formation energies derived from DFT calculations reveals that the concentration of isolated $\mathrm{Lu}$ and $\mathrm{Al}$ vacancies as dominant acceptor defects is reduced by $\mathrm{Li}$ codoping, whilst the shallow ${\mathrm{Li}}_{i}$ interstitial defects and the deep ${V}_{O}$ oxygen vacancies are introduced simultaneously. We propose that the lowering of hole trapping at defects resulting from $\mathrm{Li}$ codoping contributes to the scintillation-yield enhancement.}, number={6}, journal={PHYSICAL REVIEW APPLIED}, author={Wu, Yuntao and Yang, Ge and Han, Dan and Liu, Ming and Hawari, Ayman and Du, Mao-Hua and Peng, Jing and Foster, Camera and Chen, Shiyou and Koschan, Merry and et al.}, year={2020}, month={Jun} }
 @article{zhang_chung_huang_vetter_seyitliyev_sun_gundogdu_castellano_danilov_yang_2020, title={Towards radiation detection using Cs2AgBiBr6 double perovskite single crystals}, volume={269}, ISSN={0167-577X}, url={http://dx.doi.org/10.1016/j.matlet.2020.127667}, DOI={10.1016/j.matlet.2020.127667}, abstractNote={In this work, we studied the optical- and electrical- properties of emerging Cs2AgBiBr6 double perovskite single crystals and demonstrated their potential for detecting ionizing radiation. We prepared Cs2AgBiBr6 double perovskite single crystals from a saturated aqueous solution. Low-temperature photoluminescence (PL) was employed to determine the bandgap energies of Cs2AgBiBr6, which are 2.00 eV (indirect) and 2.26 eV (direct) respectively. Using the space charge limited current method, we estimated the density of trap states and mobility of charge carriers as 1.44 × 1010 cm−3 and 7.02 cm2/V-s respectively. A lower bound value of the mobility-lifetime (μ-τ) product of 2.48 × 10−3 cm2/V was determined using 450 nm laser excitation, which was sufficient for ensuring a long drift distance of charge carriers for several radiation detector applications. Furthermore, we tested the direct response of Cs2AgBiBr6 single crystals to X-ray radiation. Our Cs2AgBiBr6 single crystal device with gold electrodes deposited on the two parallel surfaces exhibited excellent linear response to low energy X-rays.}, journal={Materials Letters}, publisher={Elsevier BV}, author={Zhang, Zheng and Chung, Ching-Chang and Huang, Zhengjie and Vetter, Eric and Seyitliyev, Dovletgeldi and Sun, Dali and Gundogdu, Kenan and Castellano, Felix N. and Danilov, Evgeny O. and Yang, Ge}, year={2020}, month={Jun}, pages={127667} }
 @article{roy_camarda_cui_gul_yang_zazvorka_dedic_franc_james_2019, title={Evaluation of CdZnTeSe as a high-quality gamma-ray spectroscopic material with better compositional homogeneity and reduced defects}, volume={9}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-019-43778-3}, abstractNote={Abstract}, journal={SCIENTIFIC REPORTS}, author={Roy, Utpal N. and Camarda, Giuseppe S. and Cui, Yonggang and Gul, Rubi and Yang, Ge and Zazvorka, Jakub and Dedic, Vaclav and Franc, Jan and James, Ralph B.}, year={2019}, month={May} }
 @article{roy_camarda_cui_gul_hossain_yang_okobiah_egarievwe_james_2019, title={Growth of CdMnTe free of large Te inclusions using the vertical Bridgman technique}, volume={509}, ISSN={["1873-5002"]}, DOI={10.1016/j.jcrysgro.2018.12.026}, abstractNote={We grew Cd1-xMnxTe crystals with a nominal composition of 5% Mn and 95% Cd using the vertical Bridgman technique. We were able to grow crystals from as-received starting material that were free of secondary phases, such as Te inclusions with a size > 1-µm diameter, without adding compensating Cd to the initial charge. The Te precipitations (size < 1-µm diameter) were found to segregate towards the last-to-freeze section of the ingot. Te inclusions with a size 5–7 µm were observed at the grain boundary located near the last-to-freeze section, while the bottom and middle parts of the ingot showed no Te inclusions, even at the grain boundaries. X-ray topographic analysis was used to characterize the distribution of thermal stress in the ingot.}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Roy, U. N. and Camarda, G. S. and Cui, Y. and Gul, R. and Hossain, A. and Yang, G. and Okobiah, O. K. and Egarievwe, S. U. and James, R. B.}, year={2019}, month={Mar}, pages={35–39} }
 @article{hany_yang_zhou_sun_gundogdu_seyitliyev_danilov_castellano_sun_vetter_et al._2019, title={Low temperature cathodoluminescence study of Fe-doped β-Ga2O3}, volume={257}, ISSN={0167-577X}, url={http://dx.doi.org/10.1016/j.matlet.2019.126744}, DOI={10.1016/j.matlet.2019.126744}, abstractNote={Optical and electrical properties along the b-axis of Fe-doped β-Ga2O3 were studied using low temperature cathodoluminescence (CL) spectroscopy, optical absorption spectroscopy and current-voltage (IV) measurements. The optical absorption spectroscopy showed an absorption edge without near edge shoulder and the corresponding optical bandgap was calculated to be 4.45 eV using direct band gap treatment. The temperature dependent CL measurements exhibited a strong blue to ultraviolet (UV) band composed of multiple low intensity peaks in the blue range, a main blue peak, a main UV peak, and a weak UV band from the as-grown Fe-doped β-Ga2O3. After a controlled annealing in air, the emissions changed to a red to near infrared (R-NIR) band with two sharp peaks and an UV band that is resolved at room temperature to three UV broad peaks. The R-NIR sharp peaks from the air-annealed sample were ascribed to incorporation of nitrogen during air annealing.}, journal={Materials Letters}, publisher={Elsevier BV}, author={Hany, Ibrahim and Yang, Ge and Zhou, Chuanzhen Elaine and Sun, Cheng and Gundogdu, Kenan and Seyitliyev, Dovletgeldi and Danilov, Evgeny O. and Castellano, Felix N. and Sun, Dali and Vetter, Eric and et al.}, year={2019}, month={Dec}, pages={126744} }
 @article{zhang_yang_zhou_chung_hany_2019, title={Optical and electrical properties of all-inorganic Cs2AgBiBr6 double perovskite single crystals}, volume={9}, ISSN={["2046-2069"]}, url={https://doi.org/10.1039/C9RA04045E}, DOI={10.1039/c9ra04045e}, abstractNote={Temperature-dependent resistivity and cathodoluminescence (CL) measurements of solution-processed Cs2AgBiBr6 double perovskite single crystals.}, number={41}, journal={RSC ADVANCES}, publisher={Royal Society of Chemistry (RSC)}, author={Zhang, Zheng and Yang, Ge and Zhou, Chuanzhen and Chung, Ching-Chang and Hany, Ibrahim}, year={2019}, month={Aug}, pages={23459–23464} }
 @article{roy_camarda_cui_gul_hossain_yang_zazvorka_dedic_franc_james_2019, title={Role of selenium addition to CdZnTe matrix for room-temperature radiation detector applications}, volume={9}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-018-38188-w}, abstractNote={Abstract}, journal={SCIENTIFIC REPORTS}, author={Roy, U. N. and Camarda, G. S. and Cui, Y. and Gul, R. and Hossain, A. and Yang, G. and Zazvorka, J. and Dedic, V. and Franc, J. and James, R. B.}, year={2019}, month={Feb} }
 @article{bolotnikov_camarda_geronimo_fried_hodges_hossain_kim_mahler_giraldo_vernon_et al._2018, title={A 4×4 array module of position-sensitive virtual Frisch-grid CdZnTe detectors for gamma-ray imaging spectrometers}, volume={954}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2018.07.090}, DOI={10.1016/j.nima.2018.07.090}, abstractNote={Arrays of position-sensitive virtual Frisch-grid CdZnTe (CZT) detectors offer an economical approach to making high efficiency and high energy resolution gamma cameras for spectroscopy and imaging of radioactive sources. There are many application areas for such instruments including gamma-rays astronomy, medical and industrial imaging, nonproliferation and nuclear safeguards. Here we present the test results from a 4×4 array module coupled to the front-end ASIC. The array houses 16 detectors made of 6×6×20 mm3 CZT crystals. Each crystal is encapsulated inside an ultrathin polyester shell and furnished with four 5-mm-wide charge-sensing pads placed near the anode on each side of the detector. The pad’s signals are used to measure X–Y coordinates while the cathode signals give the interaction depths (Z coordinates). Combined together the signals provide 3D position information of the interaction points which can be used to correct the detector response non-uniformity. This allows developers to use standard grade (unselected) CZT crystals while retaining high spectroscopic performance comparable with that of the H3D pixelated detectors. The array’s design provides flexibility to replace individual detectors and extend their sizes, potentially increasing upwards of 4 cm in height. We started development of position-sensitive VFG detectors several years ago and today this technology has reached a high-maturity level and is ready to use in practical applications.}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Bolotnikov, A.E. and Camarda, G.S. and Geronimo, G. De and Fried, J. and Hodges, D. and Hossain, A. and Kim, K. and Mahler, G. and Giraldo, L. Ocampo and Vernon, E. and et al.}, year={2018}, month={Jul} }
 @article{roy_camarda_cui_gul_yang_james_2018, title={Charge-transport properties of as-grown Cd1-xZnxTe1-ySey by the traveling heater method}, volume={8}, ISSN={["2158-3226"]}, DOI={10.1063/1.5064373}, abstractNote={In this article, we report on the charge-transport characteristics of a new quaternary material Cd1-xZnxTe1-ySey (CZTS) grown by the Traveling Heater Method (THM). The as-grown CZTS material was found to possess fewer Te inclusions than CZT†. Moreover, high resistivity of ∼1-2x1010 ohm-cm was achieved, meeting the requirements of most gamma-ray detector applications. The mobility-lifetime product for electrons [(μτ)e] was measured to be ∼4x10-3 cm2/V. The energy resolution for the quasi-hemispherical detector fabricated from the as-grown CZTS ingot obtained was ∼2.8% (FWHM) at 662 keV.}, number={12}, journal={AIP ADVANCES}, author={Roy, U. N. and Camarda, G. S. and Cui, Y. and Gul, R. and Yang, G. and James, R. B.}, year={2018}, month={Dec} }
 @article{roy_okobiah_camarda_cui_gul_hossain_yang_egarievwe_james_2018, title={Growth and characterization of detector-grade CdMnTe by the vertical Bridgman technique}, volume={8}, ISSN={["2158-3226"]}, DOI={10.1063/1.5040362}, abstractNote={We grew Cd1-xMnxTe crystals with a nominal Mn concentration of 5% by the vertical Bridgman growth technique. The compositional variation along the length of the grown ingot was studied by powder X-ray diffraction. The composition was found to be uniform along the growth direction. The achieved resistivity was 1-2.5 x1010 ohm-cm with a mobility-lifetime (μτ) product value for electrons of ∼1.7x10-3 cm2/V. An energy resolution of ∼7.5% at 662 keV was achieved for a 9-mm long Frisch grid detector fabricated from an ingot grown using as-received starting materials.}, number={10}, journal={AIP ADVANCES}, author={Roy, U. N. and Okobiah, O. K. and Camarda, G. S. and Cui, Y. and Gul, R. and Hossain, A. and Yang, G. and Egarievwe, S. U. and James, R. B.}, year={2018}, month={Oct} }
 @article{ocampo giraldo_bolotnikov_camarda_de geronimo_fried_gul_hodges_hossain_ünlü_vernon_et al._2018, title={Study of sub-pixel position resolution with time-correlated transient signals in 3D pixelated CdZnTe detectors with varying pixel sizes}, volume={884}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2017.12.024}, DOI={10.1016/J.NIMA.2017.12.024}, abstractNote={We evaluated the sub-pixel position resolution achievable in large-volume CdZnTe pixelated detectors with conventional pixel patterns and for several different pixel sizes: 2.8 mm, 1.72 mm, 1.4 mm and 0.8 mm. Achieving position resolution below the physical dimensions of pixels (sub-pixel resolution) is a practical path for making high-granularity position-sensitive detectors, <100 μm, using a limited number of pixels dictated by the mechanical constraints and multi-channel readout electronics. High position sensitivity is important for improving the imaging capability of CZT gamma cameras. It also allows for making more accurate corrections of response non-uniformities caused by crystal defects, thus enabling use of standard-grade (unselected) and less expensive CZT crystals for producing large-volume position-sensitive CZT detectors feasible for many practical applications. We analyzed the digitized charge signals from a representative 9 pixels and the cathode, generated using a pulsed-laser light beam focused down to 10 μm (650 nm) to scan over a selected 3×3 pixel area. We applied our digital pulse processing technique to the time-correlated signals captured from adjacent pixels to achieve and evaluate the capability for sub-pixel position resolution. As an example, we also demonstrated an application of 3D corrections to improve the energy resolution and positional information of the events for the tested detectors.}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Ocampo Giraldo, L. and Bolotnikov, A.E. and Camarda, G.S. and De Geronimo, G. and Fried, J. and Gul, R. and Hodges, D. and Hossain, A. and Ünlü, K. and Vernon, E. and et al.}, year={2018}, month={Mar}, pages={136–139} }
 @article{gul_roy_camarda_hossain_yang_vanier_lordi_varley_james_2017, title={A comparison of point defects in Cd1−xZnxTe1−ySey crystals grown by Bridgman and traveling heater methods}, volume={121}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.4979012}, DOI={10.1063/1.4979012}, abstractNote={In this paper, the properties of point defects in Cd1−xZnxTe1−ySey (CZTS) radiation detectors are characterized using deep-level transient spectroscopy and compared between materials grown using two different methods, the Bridgman method and the traveling heater method. The nature of the traps was analyzed in terms of their capture cross-sections and trap concentrations, as well as their effects on the measured charge-carrier trapping and de-trapping times, and then compared for the two growth techniques. The results revealed that Se addition to CdZnTe can reduce the VCd− concentration. In Travelling Heater Method (THM) and Bridgman Method (BM) grown CZTS detectors, besides a few similarities in the shallow and medium energy traps, there were major differences in the deep traps. It was observed that the excess-Te and lower growth-temperature conditions in THM-grown CZTS led to a complete compensation of VCd− and two additional traps (attributed to Tei− and TeCd++ appearing at around Ev + 0.26 eV and Ec − 0.78 eV, respectively). The 1.1-eV deep trap related to large Te secondary phases was a dominant trap in the BM-grown CZTS crystals. In addition to i-DLTS data, the effects of point defects induced due to different processing techniques on the detector's resistivity, spectral response to gammas, and μτ product were determined.}, number={12}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Gul, R. and Roy, U. N. and Camarda, G. S. and Hossain, A. and Yang, G. and Vanier, P. and Lordi, V. and Varley, J. and James, R. B.}, year={2017}, month={Mar}, pages={125705} }
 @article{roy_camarda_cui_gul_hossain_yang_mundle_pradhan_james_2017, title={Assessment of a new ZnO:Al contact to CdZnTe for X- and gamma-ray detector applications}, volume={7}, ISSN={2158-3226}, url={http://dx.doi.org/10.1063/1.5001701}, DOI={10.1063/1.5001701}, abstractNote={The large mismatch of the coefficients of thermal expansion (CTE) between the metal contact and CdZnTe exerts thermal stress at the metal/CZT interface, which causes mechanical degradation of the contact in addition to the poor adhesion of the metallic thin film to CZT. To form a reliable and stable interface, the contact material should have better adhesion and a close match of the coefficients of thermal expansion with CZT/CdTe. Here, we report on our investigations of a novel non-metallic contact layer for use in radiation detector applications. The proposed ZnO:Al contact layer offers better adhesion due to the oxide interface, higher hardness and better matching of the CTE with CZT. It has high prospects for a reliable and stable device structure that can serve as a replacement to the common metallic electrodes used today. We evaluated AZO contacts to CZT and extracted the electronic characteristics, such as resistivity and mobility-lifetime product of electrons, and compared the results of the same characterization measurements for CZT with gold contacts. The present observations showed that the characteristics of CZT detectors with AZO contacts are nearly identical to the same detectors with gold contacts.}, number={9}, journal={AIP Advances}, publisher={AIP Publishing}, author={Roy, U. N. and Camarda, G. S. and Cui, Y. and Gul, R. and Hossain, A. and Yang, G. and Mundle, R. M. and Pradhan, A. K. and James, R. B.}, year={2017}, month={Sep}, pages={095216} }
 @article{hossain_bolotnikov_camarda_cui_gul_roy_yang_james_2017, title={Direct observation of influence of secondary-phase defects on CZT detector response}, volume={470}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/J.JCRYSGRO.2017.04.002}, DOI={10.1016/J.JCRYSGRO.2017.04.002}, abstractNote={Commercial detector-grade cadmium zinc telluride (CZT) crystals still suffer from various types of extended defects, e.g., dislocations, micro-grains, grain boundaries, and Te-rich secondary phases. Most of these defects cannot readily be identified and characterized using conventional techniques, though they are believed to be the dominant factor causing non-uniformity in the detector response. In this work, we revealed and characterized these secondary-phase defects in CZT crystals by employing multiple advanced techniques, e.g. X-ray diffraction topography, micro-scale X-ray response mapping, chemical etching and infrared microscopy. We then evaluate the detector performance of the crystals by recording high spatial-resolution raster scans of the charge collection and spectral response. We directly correlated the influence of the secondary-phase defects on the performance of the detector responses. The experimental results exhibit clear evidence of the undesirable effects of extended defects on the performance of commercial CZT radiation detectors.}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Hossain, A. and Bolotnikov, A.E. and Camarda, G.S. and Cui, Y. and Gul, R. and Roy, U.N. and Yang, G. and James, R.B.}, year={2017}, month={Jul}, pages={99–103} }
 @article{giraldo_bolotnikov_camarda_cheng_de geronimo_mcgilloway_fried_hodges_hossain_ünlü_et al._2017, title={Using a pulsed laser beam to investigate the feasibility of sub-pixel position resolution with time-correlated transient signals in 3D pixelated CdZnTe detectors}, volume={867}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2017.04.030}, DOI={10.1016/J.NIMA.2017.04.030}, abstractNote={We evaluated the X-Y position resolution achievable in 3D pixelated detectors by processing the signal waveforms readout from neighboring pixels. In these measurements we used a focused light beam, down to 10 μm, generated by a ∼1 mW pulsed laser (650 nm) to carry out raster scans over selected 3×3 pixel areas, while recording the charge signals from the 9 pixels and the cathode using two synchronized digital oscilloscopes.}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Giraldo, L. Ocampo and Bolotnikov, A.E. and Camarda, G.S. and Cheng, S. and De Geronimo, G. and McGilloway, A. and Fried, J. and Hodges, D. and Hossain, A. and Ünlü, K. and et al.}, year={2017}, month={Sep}, pages={7–14} }
 @article{roy_camarda_cui_gu_gul_hossain_yang_egarievwe_james_2016, title={Growth and characterization of CdMnTe by the vertical Bridgman technique}, volume={437}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/J.JCRYSGRO.2015.12.017}, DOI={10.1016/J.JCRYSGRO.2015.12.017}, abstractNote={We grew Cd1−xMnx Te crystals with a nominal Mn concentration of 5% by the vertical Bridgman growth technique. The structural quality of the crystal was evaluated by white beam X-ray topography in the National Synchrotron Light Source (NSLS) facility at Brookhaven National Laboratory (BNL). We observed that the crystal was free from a sub-grain boundary network, as revealed by X-ray topography and verified by our etching study. The concentration of the secondary phases, averaged over the entire ingot, was 2–3 times lower than in conventional Bridgman grown cadmium zinc telluride (CZT) crystals.}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Roy, U.N. and Camarda, G.S. and Cui, Y. and Gu, G. and Gul, R. and Hossain, A. and Yang, G. and Egarievwe, S.U. and James, R.B.}, year={2016}, month={Mar}, pages={53–58} }
 @article{roy_mundle_camarda_cui_gul_hossain_yang_pradhan_james_2016, title={Novel ZnO:Al contacts to CdZnTe for X- and gamma-ray detectors}, volume={6}, ISSN={2045-2322}, url={http://dx.doi.org/10.1038/SREP26384}, DOI={10.1038/SREP26384}, abstractNote={Abstract}, number={1}, journal={Scientific Reports}, publisher={Springer Science and Business Media LLC}, author={Roy, U. N. and Mundle, R. M. and Camarda, G. S. and Cui, Y. and Gul, R. and Hossain, A. and Yang, G. and Pradhan, A. K. and James, R. B.}, year={2016}, month={May} }
 @article{gul_cui_bolotnikov_camarda_egarievwe_hossain_roy_yang_edgar_nwagwu_et al._2016, title={Photocurrent response of B12As2 crystals to blue light, and its temperature- dependent electrical characterizations}, volume={6}, ISSN={2158-3226}, url={http://dx.doi.org/10.1063/1.4941937}, DOI={10.1063/1.4941937}, abstractNote={With the global shortage of 3He gas, researchers worldwide are looking for alternative materials for detecting neutrons. Among the candidate materials, semiconductors are attractive because of their light weight and ease in handling. Currently, we are looking into the suitability of boron arsenide (B12As2) for this specific application. As the first step in evaluating the material qualitatively, the photo-response of B12As2 bulk crystals to light with different wavelengths was examined. The crystals showed photocurrent response to a band of 407- and 470- nm blue light. The maximum measured photoresponsivity and the photocurrent density at 0.7 V for 470 nm blue light at room temperature were 0.25 A ⋅ W−1 and 2.47 mA ⋅ cm−2, respectively. In addition to photo current measurements, the electrical properties as a function of temperature (range: 50-320 K) were measured. Reliable data were obtained for the low-temperature I-V characteristics, the temperature dependence of dark current and its density, and the resistivity variations with temperature in B12As2 bulk crystals. The experiments showed an exponential dependence on temperature for the dark current, current density, and resistivity; these three electrical parameters, respectively, had a variation of a few nA to μA, 1-100 μA ⋅ cm−2 and 7.6x105-7.7x103 Ω ⋅ cm, for temperature increasing from 50 K to 320 K. The results from this study reported the first photoresponse and demonstrated that B12As2 is a potential candidate for thermal-neutron detectors.}, number={2}, journal={AIP Advances}, publisher={AIP Publishing}, author={Gul, R. and Cui, Y. and Bolotnikov, A. E. and Camarda, G. S. and Egarievwe, S. U. and Hossain, A. and Roy, U. N. and Yang, G. and Edgar, J. H. and Nwagwu, U. and et al.}, year={2016}, month={Feb}, pages={025206} }
 @article{gul_roy_egarievwe_bolotnikov_camarda_cui_hossain_yang_james_2016, title={Point defects: Their influence on electron trapping, resistivity, and electron mobility-lifetime product in CdTexSe1−x detectors}, volume={119}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.4939647}, DOI={10.1063/1.4939647}, abstractNote={In this research, we assessed the abundance of point defects and their influence on the resistivity, the electron mobility-lifetime (μτe) product, and the electron trapping time in CdTeSe crystals grown under different conditions using the traveling heater method. We used current-deep level transient spectroscopy to determine the traps' energy, their capture cross-section, and their concentration. Further, we used these data to determine the trapping and de-trapping times for the charge carriers. The data show that detectors with a lower concentration of In-dopant have a higher density of A-centers and Cd double vacancies (VCd- -). The high concentrations of VCd- - and A-centers, along with the deep trap at 0.86 eV and low density of 1.1 eV energy traps, are the major cause of the detectors' low resistivity, and most probably, a major contributor to the low μτe product. Our results indicate that the energy levels of point defects in the bandgap, their concentrations, capture cross-sections, and their trapping and de-trapping times play an important role in the detector's performance, especially for devices that rely solely on electron transport.}, number={2}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Gul, R. and Roy, U. N. and Egarievwe, S. U. and Bolotnikov, A. E. and Camarda, G. S. and Cui, Y. and Hossain, A. and Yang, G. and James, R. B.}, year={2016}, month={Jan}, pages={025702} }
 @article{bolotnikov_camarda_cui_de geronimo_eger_emerick_fried_hossain_roy_salwen_et al._2016, title={Use of high-granularity CdZnTe pixelated detectors to correct response non-uniformities caused by defects in crystals}, volume={805}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2015.08.051}, DOI={10.1016/J.NIMA.2015.08.051}, abstractNote={Following our successful demonstration of the position-sensitive virtual Frisch-grid detectors, we investigated the feasibility of using high-granularity position sensing to correct response non-uniformities caused by the crystal defects in CdZnTe (CZT) pixelated detectors. The development of high-granularity detectors able to correct response non-uniformities on a scale comparable to the size of electron clouds opens the opportunity of using unselected off-the-shelf CZT material, whilst still assuring high spectral resolution for the majority of the detectors fabricated from an ingot. Here, we present the results from testing 3D position-sensitive 15×15×10 mm3 pixelated detectors, fabricated with conventional pixel patterns with progressively smaller pixel sizes: 1.4, 0.8, and 0.5 mm. We employed the readout system based on the H3D front-end multi-channel ASIC developed by BNL's Instrumentation Division in collaboration with the University of Michigan. We use the sharing of electron clouds among several adjacent pixels to measure locations of interaction points with sub-pixel resolution. By using the detectors with small-pixel sizes and a high probability of the charge-sharing events, we were able to improve their spectral resolutions in comparison to the baseline levels, measured for the 1.4-mm pixel size detectors with small fractions of charge-sharing events. These results demonstrate that further enhancement of the performance of CZT pixelated detectors and reduction of costs are possible by using high spatial-resolution position information of interaction points to correct the small-scale response non-uniformities caused by crystal defects present in most devices.}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Bolotnikov, A.E. and Camarda, G.S. and Cui, Y. and De Geronimo, G. and Eger, J. and Emerick, A. and Fried, J. and Hossain, A. and Roy, U. and Salwen, C. and et al.}, year={2016}, month={Jan}, pages={41–54} }
 @article{bolotnikov_ackley_camarda_cherches_cui_de geronimo_fried_hodges_hossain_lee_et al._2015, title={An array of virtual Frisch-grid CdZnTe detectors and a front-end application-specific integrated circuit for large-area position-sensitive gamma-ray cameras}, volume={86}, ISSN={0034-6748 1089-7623}, url={http://dx.doi.org/10.1063/1.4927455}, DOI={10.1063/1.4927455}, abstractNote={We developed a robust and low-cost array of virtual Frisch-grid CdZnTe detectors coupled to a front-end readout application-specific integrated circuit (ASIC) for spectroscopy and imaging of gamma rays. The array operates as a self-reliant detector module. It is comprised of 36 close-packed 6 × 6 × 15 mm3 detectors grouped into 3 × 3 sub-arrays of 2 × 2 detectors with the common cathodes. The front-end analog ASIC accommodates up to 36 anode and 9 cathode inputs. Several detector modules can be integrated into a single- or multi-layer unit operating as a Compton or a coded-aperture camera. We present the results from testing two fully assembled modules and readout electronics. The further enhancement of the arrays’ performance and reduction of their cost are possible by using position-sensitive virtual Frisch-grid detectors, which allow for accurate corrections of the response of material non-uniformities caused by crystal defects.}, number={7}, journal={Review of Scientific Instruments}, publisher={AIP Publishing}, author={Bolotnikov, A. E. and Ackley, K. and Camarda, G. S. and Cherches, C. and Cui, Y. and De Geronimo, G. and Fried, J. and Hodges, D. and Hossain, A. and Lee, W. and et al.}, year={2015}, month={Jul}, pages={073114} }
 @article{hossain_bolotnikov_camarda_cui_gul_kim_roy_tong_yang_james_2015, title={Analysis of Defects on Chemically-Treated CdZnTe Surfaces}, volume={44}, ISSN={0361-5235 1543-186X}, url={http://dx.doi.org/10.1007/S11664-015-3742-4}, DOI={10.1007/S11664-015-3742-4}, number={9}, journal={Journal of Electronic Materials}, publisher={Springer Science and Business Media LLC}, author={Hossain, A. and Bolotnikov, A. E. and Camarda, G. S. and Cui, Y. and Gul, R. and Kim, K.-H. and Roy, U. N. and Tong, X. and Yang, G. and James, R. B.}, year={2015}, month={Mar}, pages={3018–3022} }
 @article{roy_bolotnikov_camarda_cui_hossain_lee_lee_tappero_yang_cui_et al._2015, title={Compositional homogeneity and X-ray topographic analyses of CdTe Se1− grown by the vertical Bridgman technique}, volume={411}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/J.JCRYSGRO.2014.10.057}, DOI={10.1016/J.JCRYSGRO.2014.10.057}, abstractNote={We grew CdTexSe1−x crystals with nominal Se concentrations of 5%, 7%, and 10% by the vertical Bridgman technique, and evaluated their compositional homogeneity and structural quality at the NSLS’ X-ray fluorescence and white beam X-ray topography beam lines. Both X-ray fluorescence and photoluminescence mapping revealed very high compositional homogeneity of the CdTexSe1−x crystals. We noted that those crystals with higher concentrations of Se were more prone to twinning than those with a lower content. The crystals were fairly free from strains and contained low concentrations of sub-grain boundaries and their networks.}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Roy, U.N. and Bolotnikov, A.E. and Camarda, G.S. and Cui, Y. and Hossain, A. and Lee, K. and Lee, W. and Tappero, R. and Yang, Ge and Cui, Y. and et al.}, year={2015}, month={Feb}, pages={34–37} }
 @article{roy_bolotnikov_camarda_cui_hossain_lee_lee_tappero_yang_gul_et al._2015, title={High compositional homogeneity of CdTexSe1−x crystals grown by the Bridgman method}, volume={3}, ISSN={2166-532X}, url={http://dx.doi.org/10.1063/1.4907250}, DOI={10.1063/1.4907250}, abstractNote={We obtained high-quality CdTexSe1−x (CdTeSe) crystals from ingots grown by the vertical Bridgman technique. The compositional uniformity of the ingots was evaluated by X-ray fluorescence at BNL’s National Synchrotron Light Source X27A beam line. The compositional homogeneity was highly uniform throughout the ingot, and the effective segregation coefficient of Se was ∼1.0. This high uniformity offers potential opportunity to enhance the yield of the materials for both infrared substrate and radiation-detector applications, so greatly lowering the cost of production and also offering us the prospect to grow large-diameter ingots for use as large-area substrates and for producing higher efficiency gamma-ray detectors. The concentration of secondary phases was found to be much lower, by eight- to ten fold compared to that of conventional CdxZn1−xTe (CdZnTe or CZT).}, number={2}, journal={APL Materials}, publisher={AIP Publishing}, author={Roy, U. N. and Bolotnikov, A. E. and Camarda, G. S. and Cui, Y. and Hossain, A. and Lee, K. and Lee, W. and Tappero, R. and Yang, G. and Gul, R. and et al.}, year={2015}, month={Feb}, pages={026102} }
 @article{hossain_gu_bolotnikov_camarda_cui_roy_yang_liu_zhong_schneeloch_et al._2015, title={Material and detector properties of cadmium manganese telluride (Cd1−Mn Te) crystals grown by the modified floating-zone method}, volume={784}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2014.12.060}, DOI={10.1016/J.NIMA.2014.12.060}, abstractNote={We demonstrated the material- and radiation-detection properties of cadmium manganese telluride (Cd1−xMnxTe; x=0.06), a wide-band-gap semiconductor crystal grown by the modified floating-zone method. We investigated the presence of various bulk defects, such as Te inclusions, twins, and dislocations of several as-grown indium-doped Cd1−xMnxTe crystals using different techniques, viz., IR transmission microscopy, and chemical etching. We then fabricated four planar detectors from selected CdMnTe crystals, characterized their electrical properties, and tested their performance as room-temperature X- and gamma-ray detectors. Our experimental results show that CMT crystals grown by the modified floating zone method apparently are free from Te inclusions. However, we still need to optimize our growth parameters to attain high-resistivity, large-volume single-crystal CdMnTe.}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Hossain, A. and Gu, G.D. and Bolotnikov, A.E. and Camarda, G.S. and Cui, Y. and Roy, U.N. and Yang, G. and Liu, T. and Zhong, R. and Schneeloch, J. and et al.}, year={2015}, month={Jun}, pages={33–36} }
 @article{egarievwe_yang_egarievwe_okwechime_gray_hales_hossain_camarda_bolotnikov_james_2015, title={Post-growth annealing of Bridgman-grown CdZnTe and CdMnTe crystals for room-temperature nuclear radiation detectors}, volume={784}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2015.02.006}, DOI={10.1016/J.NIMA.2015.02.006}, abstractNote={Bridgman-grown cadmium zinc telluride (CdZnTe or CZT) and cadmium manganese telluride (CdMnTe or CMT) crystals often have Te inclusions that limit their performances as X-ray- and gamma-ray-detectors. We present here the results of post-growth thermal annealing aimed at reducing and eliminating Te inclusions in them. In a 2D analysis, we observed that the sizes of the Te inclusions declined to 92% during a 60-h annealing of CZT at 510 °C under Cd vapor. Further, tellurium inclusions were eliminated completely in CMT samples annealed at 570 °C in Cd vapor for 26 h, whilst their electrical resistivity fell by an order of 102. During the temperature-gradient annealing of CMT at 730 °C and an 18 °C/cm temperature gradient for 18 h in a vacuum of 10−5 mbar, we observed the diffusion of Te from the sample, so causing a reduction in size of the Te inclusions. For CZT samples annealed at 700 °C in a 10 °C/cm temperature gradient, we observed the migration of Te inclusions from a low-temperature region to a high one at 0.022 μm/s. During the temperature-gradient annealing of CZT in a vacuum of 10−5 mbar at 570 °C and 30 °C/cm for 18 h, some Te inclusions moved toward the high-temperature side of the wafer, while other inclusions of the same size, i.e., 10 µm in diameter, remained in the same position. These results show that the migration, diffusion, and reaction of Te with Cd in the matrix of CZT- and CMT-wafers are complex phenomena that depend on the conditions in local regions, such as composition and structure, as well as on the annealing conditions.}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Egarievwe, Stephen U. and Yang, Ge and Egarievwe, Alexander A. and Okwechime, Ifechukwude O. and Gray, Justin and Hales, Zaveon M. and Hossain, Anwar and Camarda, Giuseppe S. and Bolotnikov, Aleksey E. and James, Ralph B.}, year={2015}, month={Jun}, pages={51–55} }
 @article{gul_roy_bolotnikov_camarda_cui_hossain_lee_yang_cui_burger_et al._2015, title={Research Update: Point defects in CdTexSe1−x crystals grown from a Te-rich solution for applications in detecting radiation}, volume={3}, ISSN={2166-532X}, url={http://dx.doi.org/10.1063/1.4917270}, DOI={10.1063/1.4917270}, abstractNote={We investigated cadmium telluride selenide (CdTeSe) crystals, newly grown by the Traveling Heater Method (THM), for the presence and abundance of point defects. Current Deep Level Transient spectroscopy (I-DLTS) was used to determine the energies of the traps, their capture cross sections, and densities. The bias across the detectors was varied from 1 to 30 V. Four types of point defects were identified, ranging from 10 meV to 0.35 eV. Two dominant traps at energies of 0.18 eV and 0.14 eV were studied in depth. Cd vacancies are found at lower concentrations than other point defects present in the material.}, number={4}, journal={APL Materials}, publisher={AIP Publishing}, author={Gul, R. and Roy, U. N. and Bolotnikov, A. E. and Camarda, G. S. and Cui, Y. and Hossain, A. and Lee, W. and Yang, G. and Cui, Y. and Burger, A. and et al.}, year={2015}, month={Apr}, pages={040702} }
 @article{yang_gu_bolotnikov_cui_camarda_hossain_roy_kivi_liu_james_2015, title={Structural, electrical, and optical properties of CdMnTe crystals grown by modified floating-zone technique}, volume={11}, ISSN={1738-8090 2093-6788}, url={http://dx.doi.org/10.1007/S13391-015-4261-4}, DOI={10.1007/S13391-015-4261-4}, number={3}, journal={Electronic Materials Letters}, publisher={Springer Science and Business Media LLC}, author={Yang, Ge and Gu, Genda and Bolotnikov, Aleksey E. and Cui, Yonggang and Camarda, Giuseppe S. and Hossain, Anwar and Roy, Utpal N. and Kivi, Nicholas and Liu, Tiansheng and James, Ralph B.}, year={2015}, month={May}, pages={500–504} }
 @article{roy_bolotnikov_camarda_cui_hossain_lee_yang_james_2014, title={Evaluation of CdTexSe1−x crystals grown from a Te-rich solution}, volume={389}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/J.JCRYSGRO.2013.11.074}, DOI={10.1016/J.JCRYSGRO.2013.11.074}, abstractNote={We characterized the structural quality of CdTexSe1−x crystals grown by the Traveling Heater Method (THM) from a Te-rich solution using Synchrotron White Beam X-ray Diffraction Topography in the reflection mode. Structural defects were also studied by chemical etching of the crystal surfaces. The crystals were found to be fairly free from strains, and they had very few sub-grain boundaries and dislocation/sub-grain boundary networks.}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Roy, U.N. and Bolotnikov, A.E. and Camarda, G.S. and Cui, Y. and Hossain, A. and Lee, K. and Yang, G. and James, R.B.}, year={2014}, month={Mar}, pages={99–102} }
 @article{roy_bolotnikov_camarda_cui_hossain_lee_marshall_yang_james_2014, title={Growth of CdTexSe1−x from a Te-rich solution for applications in radiation detection}, volume={386}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/J.JCRYSGRO.2013.09.039}, DOI={10.1016/J.JCRYSGRO.2013.09.039}, abstractNote={We grew CdTexSe1−x (CTS) crystals from a Te-rich solution by using the traveling heater method (THM). The average size distribution and concentration of Te inclusions/precipitates in these as-grown samples were measured to be ~7×104 cm−3, which is much lower than values typical for the present state-of-the-art commercial CdZnTe (CZT) material. Their low-temperature photoluminescence measurement indicates high quality of the material; however the resistivity obtained via I–V curve measurements was ~5×108 Ω-cm, which is low in comparison to that required for gamma detectors. A well-resolved alpha response peak can be detected for both planar- and hemispherical detector geometry. The (μτ)e value for our as-grown sample at room temperature was found to be ~4×10−3 cm2/V.}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Roy, U.N. and Bolotnikov, A.E. and Camarda, G.S. and Cui, Y. and Hossain, A. and Lee, K. and Marshall, M. and Yang, G. and James, R.B.}, year={2014}, month={Jan}, pages={43–46} }
 @article{hossain_bolotnikov_camarda_cui_jones_hall_kim_mwathi_tong_yang_et al._2014, title={Novel Approach to Surface Processing for Improving the Efficiency of CdZnTe Detectors}, volume={43}, ISSN={0361-5235 1543-186X}, url={http://dx.doi.org/10.1007/S11664-013-2698-5}, DOI={10.1007/S11664-013-2698-5}, number={8}, journal={Journal of Electronic Materials}, publisher={Springer Science and Business Media LLC}, author={Hossain, A. and Bolotnikov, A. E. and Camarda, G. S. and Cui, Y. and Jones, D. and Hall, J. and Kim, K. H. and Mwathi, J. and Tong, X. and Yang, G. and et al.}, year={2014}, pages={2771–2777} }
 @article{bolotnikov_camarda_cui_de geronimo_fried_hossain_lee_mahler_maritato_marshall_et al._2014, title={Publisher’s Note: “Use of high-granularity position sensing to correct response non-uniformities of CdZnTe detectors” [Appl. Phys. Lett. 104, 263503 (2014)]}, volume={105}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4894420}, DOI={10.1063/1.4894420}, abstractNote={First Page}, number={10}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Bolotnikov, A. E. and Camarda, G. S. and Cui, Y. and De Geronimo, G. and Fried, J. and Hossain, A. and Lee, K. and Mahler, G. and Maritato, M. and Marshall, M. and et al.}, year={2014}, month={Sep}, pages={109901} }
 @article{yang_bolotnikov_fochuk_camarda_hossain_roy_cui_pinder_gray_james_2014, title={Thermo-migration of Te inclusions in CdZnTe during post-growth annealing in a temperature-gradient field}, volume={11}, ISSN={1862-6351}, url={http://dx.doi.org/10.1002/PSSC.201300644}, DOI={10.1002/PSSC.201300644}, abstractNote={Abstract}, number={7-8}, journal={physica status solidi (c)}, publisher={Wiley}, author={Yang, G. and Bolotnikov, A. E. and Fochuk, P. M. and Camarda, G. S. and Hossain, A. and Roy, U. N. and Cui, Y. and Pinder, R. and Gray, J. and James, R. B.}, year={2014}, month={Mar}, pages={1328–1332} }
 @article{hossain_dowdy_bolotnikov_camarda_cui_roy_tappero_tong_yang_james_2014, title={Topographic Evaluation of the Effect of Passivation in Improving the Performance of CdZnTe Detectors}, volume={43}, ISSN={0361-5235 1543-186X}, url={http://dx.doi.org/10.1007/S11664-014-3153-Y}, DOI={10.1007/S11664-014-3153-Y}, number={8}, journal={Journal of Electronic Materials}, publisher={Springer Science and Business Media LLC}, author={Hossain, A. and Dowdy, A. and Bolotnikov, A. E. and Camarda, G. S. and Cui, Y. and Roy, U. N. and Tappero, R. and Tong, X. and Yang, G. and James, R. B.}, year={2014}, month={May}, pages={2941–2946} }
 @article{bolotnikov_camarda_cui_de geronimo_fried_hossain_lee_mahler_maritato_marshall_et al._2014, title={Use of high-granularity position sensing to correct response non-uniformities of CdZnTe detectors}, volume={104}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4883402}, DOI={10.1063/1.4883402}, abstractNote={CdZnTe (CZT) is a promising medium for room-temperature gamma-ray detectors. However, the low production yield of acceptable quality crystals hampers the use of CZT detectors for gamma-ray spectroscopy. Significant efforts have been directed towards improving quality of CZT crystals to make them generally available for radiation detectors. Another way to address this problem is to implement detector designs that would allow for more accurate and predictable correction of the charge loss associated with crystal defects. In this work, we demonstrate that high-granularity position-sensitive detectors can significantly improve the performance of CZT detectors fabricated from CZT crystals with wider acceptance boundaries, leading to an increase of their availability and expected decrease in cost.}, number={26}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Bolotnikov, A. E. and Camarda, G. S. and Cui, Y. and De Geronimo, G. and Fried, J. and Hossain, A. and Lee, K. and Mahler, G. and Maritato, M. and Marshall, M. and et al.}, year={2014}, month={Jun}, pages={263503} }
 @article{bolotnikov_camarda_cui_yang_hossain_kim_james_2013, title={Characterization and evaluation of extended defects in CZT crystals for gamma-ray detectors}, volume={379}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/J.JCRYSGRO.2013.01.048}, DOI={10.1016/J.JCRYSGRO.2013.01.048}, abstractNote={Material homogeneity is critical in achieving high-performance in all types of radiation detectors. This requirement is not inevitably satisfied in today's commercial detector-grade CdZnTe (CZT) material because it contains high concentrations of extended defects, in particular, Te inclusions, dislocation networks, and twin- and subgrain-boundaries that affect the energy resolution and the efficiency of the devices. Defects, such as grain boundaries and cracks that completely block charge-carrier transport are impermissible in CZT radiation-detectors at concentrations exceeding certain threshold values. Our group in Brookhaven National Laboratory (BNL) conducts systematic studies, detailing the roles of crystal defects in CZT detectors and the mechanisms underlying their formation and effects. We employ infrared transmission microscopy, white beam X-ray diffraction topography, and high-spatial-resolution X-ray response mapping to identify particular types of defects and reveal their relationship with the devices' performances. In this article, we summarize some of the most important results that our group obtained over the past 5 years.}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Bolotnikov, A.E. and Camarda, G.S. and Cui, Y. and Yang, G. and Hossain, A. and Kim, K. and James, R.B.}, year={2013}, month={Sep}, pages={46–56} }
 @article{hossain_yakimovich_bolotnikov_bolton_camarda_cui_franc_gul_kim_pittman_et al._2013, title={Development of Cadmium Magnesium Telluride (Cd1−xMgxTe) for room temperature X- and gamma-ray detectors}, volume={379}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2012.11.044}, DOI={10.1016/j.jcrysgro.2012.11.044}, abstractNote={Cadmium Magnesium Telluride (Cd1−xMgxTe/CMgT) offers several pronounced potential advantages over the well-studied CdZnTe and CdMnTe, possibly making it a good alternative for room-temperature X- and gamma-ray detectors. It possesses high crystallinity due to the near-similar lattice structure of CdTe (6.48 Å) and MgTe (6.42 Å). Its displays good homogeneity as the Mg segregation coefficient in CdTe is nearly 1. Furthermore, inhomogeneities in the crystal due to alloying effects can be minimized, because the optimal energy band-gap can be achieved using less Mg in CdMgTe compared to Zn and Mn needed in CdZnTe and CdMnTe. We recently grew an undoped- and a doped-ingot of CdMgTe, characterized its material properties, and tested its detection performance. We obtained some exciting results that demonstrated some of its potential advantages over the other materials. The band-gap was measured as 1.61 eV at room temperature and 1.73 eV at 4 K. The yield was predominantly single crystals with about two orders-of-magnitude fewer Te inclusions and other growth defects compared to CdZnTe and CdMnTe crystals. The measured resistivity of the undoped annealed crystal was about ∼107 Ω-cm; after doping in a second growth trial, it increased by 2–3 orders-of-magnitude (109–1010 Ω-cm). We examined the doped as-grown crystal as a radiation detector and acquired reasonably good spectral response to an Am-241 source. The estimated mu-tau value was as high as 7×10−4 cm2/V, which is an extraordinarily high value for such an early-phase investigation. We also analyzed point and extended defects using various techniques that will be discussed in this manuscript.}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Hossain, A. and Yakimovich, V. and Bolotnikov, A.E. and Bolton, K. and Camarda, G.S. and Cui, Y. and Franc, J. and Gul, R. and Kim, K-H and Pittman, H. and et al.}, year={2013}, month={Sep}, pages={34–40} }
 @article{yang_bolotnikov_cui_camarda_hossain_kim_franc_belas_james_2013, title={Low-Temperature Photoluminescence Study of CdTe:In Crystals Annealed in Molten Bismuth}, volume={42}, ISSN={0361-5235 1543-186X}, url={http://dx.doi.org/10.1007/S11664-013-2683-Z}, DOI={10.1007/S11664-013-2683-Z}, number={11}, journal={Journal of Electronic Materials}, publisher={Springer Science and Business Media LLC}, author={Yang, G. and Bolotnikov, A. E. and Cui, Y. and Camarda, G. S. and Hossain, A. and Kim, K. H. and Franc, J. and Belas, E. and James, R. B.}, year={2013}, month={Aug}, pages={3138–3141} }
 @article{yang_bolotnikov_fochuk_kopach_franc_belas_kim_camarda_hossain_cui_et al._2013, title={Post-growth thermal annealing study of CdZnTe for developing room-temperature X-ray and gamma-ray detectors}, volume={379}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2012.11.041}, DOI={10.1016/j.jcrysgro.2012.11.041}, abstractNote={Post-growth annealing is a potentially promising method of improving the properties of CZT for fabricating room-temperature X-ray and gamma-ray detectors. In this paper, we summarize some of our recent research on annealing detector-grade CZT crystals. Our results show that annealing in a Cd vapor effectively removes Te inclusions from CZT. The migration of Te inclusions was also observed for annealing in a temperature-gradient field. We recorded a loss of resistivity of the detector-grade CZT after annealing in a Cd vapor. The underlying mechanism of this loss was discussed, and solutions including two-step annealing (Cd annealing followed by Te annealing) and one-step annealing with Cd and Zn pressure control were proposed to maintain high resistivity.}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Yang, G. and Bolotnikov, A.E. and Fochuk, P.M. and Kopach, O. and Franc, J. and Belas, E. and Kim, K.H. and Camarda, G.S. and Hossain, A. and Cui, Y. and et al.}, year={2013}, month={Sep}, pages={16–20} }
 @article{yang_bolotnikov_fochuk_cui_camarda_hossain_kim_raghothamachar_roy_james_2013, title={‘Star-like’ defects in Cd-annealed CdZnTe crystals-an experimental study of their origin and formation mechanism}, volume={48}, ISSN={0232-1300}, url={http://dx.doi.org/10.1002/CRAT.201300009}, DOI={10.1002/CRAT.201300009}, abstractNote={Abstract}, number={4}, journal={Crystal Research and Technology}, publisher={Wiley}, author={Yang, G. and Bolotnikov, A. E. and Fochuk, P. M. and Cui, Y. and Camarda, G. S. and Hossain, A. and Kim, K. H. and Raghothamachar, B. and Roy, U. and James, R. B.}, year={2013}, month={Mar}, pages={221–226} }
 @article{xu_jie_bolotnikov_roy_stein_hossain_camarda_kim_yang_gul_et al._2012, title={Concentration of extended defects in CdZnTe single crystals: Effects of cooling rate after growth}, volume={355}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2012.06.024}, DOI={10.1016/j.jcrysgro.2012.06.024}, abstractNote={A1. Extended defect A1. Sub-grain boundary A1. Te inclusion A2. Cooling rate A2. Crystal growth B2. CdZnTe abstract We analyzed two CZT crystals cut from as-grown CdZnTe (CZT) ingots, the only difference between them being the rate of cooling after the crystal growth process. Using White Beam X-ray Diffraction Topography (WBXDT) and Infrared (IR) Transmission Microscopy, we identified and quantified the extended defects, e.g., Te inclusions, dislocations, and sub-grain boundaries. The effects of cooling rate on the size distribution and concentration were studied. The WBXDT and IR images of the fast-cooled crystal revealed very high density of dislocations and sub-grain boundaries, crisscrossing throughout its entire volume, extending from deep inside almost to the surface. In addition, IR analyses showed that the concentration of Te inclusions in the fast-cooled crystal (10 6 cm � 3 ) was higher than that in the slow-cooled one (10 5 cm � 3 ). For the latter, both the WBXDT and the IR images were bright and clear with low concentration of defects. We concluded that slow cooling rate can greatly reduce the number of Te inclusions and inclusion-decorated extended defects in as-grown CZT ingots.}, number={1}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Xu, L. and Jie, W. and Bolotnikov, A.E. and Roy, U.N. and Stein, J. and Hossain, A. and Camarda, G.S. and Kim, K-H. and Yang, G. and Gul, R. and et al.}, year={2012}, month={Sep}, pages={84–87} }
 @article{hossain_bolotnikov_camarda_gul_kim_kisslinger_yang_zhang_james_2012, title={Investigation of Structural Defects in CdZnTe Detector-Grade Crystals}, volume={41}, ISSN={0361-5235 1543-186X}, url={http://dx.doi.org/10.1007/S11664-012-2007-8}, DOI={10.1007/S11664-012-2007-8}, number={10}, journal={Journal of Electronic Materials}, publisher={Springer Science and Business Media LLC}, author={Hossain, A. and Bolotnikov, A.E. and Camarda, G.S. and Gul, R. and Kim, K.H. and Kisslinger, K. and Yang, G. and Zhang, L.H. and James, R.B.}, year={2012}, month={Mar}, pages={2908–2911} }
 @article{gul_keeter_rodriguez_bolotnikov_hossain_camarda_kim_yang_cui_carcelen_et al._2012, title={Point Defects in Pb-, Bi-, and In-Doped CdZnTe Detectors: Deep-Level Transient Spectroscopy (DLTS) Measurements}, volume={41}, ISSN={0361-5235 1543-186X}, url={http://dx.doi.org/10.1007/S11664-011-1802-Y}, DOI={10.1007/S11664-011-1802-Y}, abstractNote={We studied, by current deep-level transient spectroscopy (I-DLTS), point defects induced in CdZnTe detectors by three dopants: Pb, Bi, and In. Pb-doped CdZnTe detectors have a new acceptor trap at around 0.48 eV. The absence of a VCd trap suggests that all Cd vacancies are compensated by Pb interstitials after they form a deep-acceptor complex [[PbCd]+-V Cd 2− ]−. Bi-doped CdZnTe detectors had two distinct traps: a shallow trap at around 36 meV and a deep donor trap at around 0.82 eV. In detectors doped with In, we noted three well-known traps: two acceptor levels at around 0.18 eV (A-centers) and 0.31 eV (VCd), and a deep trap at around 1.1 eV.}, number={3}, journal={Journal of Electronic Materials}, publisher={Springer Science and Business Media LLC}, author={Gul, R. and Keeter, K. and Rodriguez, R. and Bolotnikov, A.E. and Hossain, A. and Camarda, G.S. and Kim, K.H. and Yang, G. and Cui, Y. and Carcelen, V. and et al.}, year={2012}, pages={488–493} }
 @article{yang_bolotnikov_fochuk_cui_camarda_hossain_kim_horace_mccall_gul_et al._2012, title={Post-growth Annealing of Cadmium Zinc Telluride Crystals for Room-Temperature Radiation Detectors}, volume={41}, ISSN={0361-5235 1543-186X}, url={http://dx.doi.org/10.1007/S11664-012-2013-X}, DOI={10.1007/S11664-012-2013-X}, abstractNote={We investigated the effects of post-growth annealing on cadmium zinc telluride crystals intended for use as room-temperature radiation detectors. Annealing under Cd vapor effectively eliminated Te inclusions. The material’s resistivity was lowered, and loss of Zn component was observed. Annealing under Cd + Zn vapors similarly removed Te inclusions. Furthermore, after exposure to the two vapors, we noted a change in the crystal surface morphology, i.e., formation of patterns of parallel lines. In contrast to annealing under Cd vapor alone, high resistivity was maintained after suitably controlling the Cd and Zn pressures.}, number={10}, journal={Journal of Electronic Materials}, publisher={Springer Science and Business Media LLC}, author={Yang, G. and Bolotnikov, A.E. and Fochuk, P.M. and Cui, Y. and Camarda, G. S. and Hossain, A. and Kim, K. H. and Horace, J. and McCall, B. and Gul, R. and et al.}, year={2012}, month={Mar}, pages={2912–2916} }
 @article{carcelén_kim_camarda_bolotnikov_hossain_yang_crocco_bensalah_dierre_diéguez_et al._2012, title={Pt coldfinger improves quality of Bridgman-grown Cd0.9Zn0.1Te:Bi crystals}, volume={338}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2011.09.031}, DOI={10.1016/j.jcrysgro.2011.09.031}, abstractNote={Cadmium zinc telluride (Cd1−xZnxTe) crystals have many applications in optoelectronics and as room-temperature detectors. We grew bismuth-doped CZT crystals by the standard Bridgman Oscillation Method, and compared them with such crystals grown in the thermal environment of a furnace modified with a Pt coldfinger (metal rod). The coldfinger serves as a tool for stabilizing the solid–liquid interface by extracting heat from the as-grown crystal, and thereby improving the ingot's crystalline quality. We detailed the crystal's quality via high-resolution X-ray diffraction (HRXRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Synchrotron-based X-ray microfluorescence (μSXRF) images, as well as by etch-pit density (EPD) measurements. Our results demonstrated that the Pt coldfinger is an effective tool for improving the quality of CZT bulk material.}, number={1}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Carcelén, V. and Kim, K.H. and Camarda, G.S. and Bolotnikov, A.E. and Hossain, A. and Yang, G. and Crocco, J. and Bensalah, H. and Dierre, F. and Diéguez, E. and et al.}, year={2012}, month={Jan}, pages={1–5} }
 @article{bolotnikov_camarda_cui_de geronimo_fried_gul_hossain_kim_yang_vernon_et al._2012, title={Rejecting incomplete charge-collection events in CdZnTe and other semiconductor detectors}, volume={664}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2011.10.066}, DOI={10.1016/J.NIMA.2011.10.066}, abstractNote={In an ideal single-carrier-type gamma ray detector, the amplitudes of the signals and the carrier drift times are correlated variables. However, if the charges produced by an incident photon are not fully collected, as is the case in CdZnTe detectors containing crystal defects, the above correlation does not hold. This permits the application of an event recognition algorithm to identify these incomplete charge collection (ICC) events, caused by the “bad” regions inside a detector, so that they can be removed from pulse height spectra. The ICC events primarily contribute to the Compton continuum and the low-energy tail of the photopeak. Thus, rejecting such events should not affect significantly the photopeak efficiency, but should improve the spectral response, e.g., the peak-to-Compton ratio, for a detector fabricated from material with relaxed crystal quality requirements. Such crystals are those currently available from vendors. The use of stronger ICC correlation-function rejection criteria can improve the energy resolution of these lower-quality crystals, but at the price of a loss in photoefficiency.}, number={1}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Bolotnikov, A.E. and Camarda, G.S. and Cui, Y. and De Geronimo, G. and Fried, J. and Gul, R. and Hossain, A. and Kim, K. and Yang, G. and Vernon, E. and et al.}, year={2012}, month={Feb}, pages={317–323} }
 @article{kim_suh_bolotnikov_fochuk_kopach_camarda_cui_hossain_yang_hong_et al._2012, title={Temperature-gradient annealing of CdZnTe under Te overpressure}, volume={354}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2012.03.058}, DOI={10.1016/j.jcrysgro.2012.03.058}, abstractNote={The performance of CdZnTe (CZT) detectors is limited not only by conventional carrier-trapping to point defects but also by trapping at macroscopic Te secondary-phase defects, such as Te inclusions and Te precipitates. The aim of this research is to remove these secondary-phase defects via thermomigration, and to obtain high resistivity of the material by creating Te antisites through annealing in a high Te overpressure. We annealed Te-rich CZT samples in the temperature range between 500 and 700 °C under Te overpressure with a temperature gradient of 50–60 °C/cm. We investigated the effects of annealing under these conditions by IR transmission microscopy, current–voltage measurements, photoluminescence, and white-beam X-ray diffraction topography (WBXDT) measurements comparing the findings with those from isothermally annealed CZT samples under Cd overpressure. We proved experimentally that Te inclusions present in Te-rich CZT melts contain void fractions. We attributed the complex defect of Te antisites with Cd vacancies in our annealing experiment as the deep level defect that pins the Fermi near the middle of the bandgap, rather than the Te antisite.}, number={1}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Kim, K.H. and Suh, J. and Bolotnikov, A.E. and Fochuk, P.M. and Kopach, O.V. and Camarda, G.S. and Cui, Y. and Hossain, A. and Yang, G. and Hong, J. and et al.}, year={2012}, month={Sep}, pages={62–66} }
 @article{hossain_xu_bolotnikov_camarda_cui_yang_kim_james_2011, title={Distribution of Te inclusions in a CdZnTe wafer and their effects on the electrical properties of fabricated devices}, volume={652}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2011.01.162}, DOI={10.1016/J.NIMA.2011.01.162}, abstractNote={We quantified the size and concentration of Te inclusions along the lateral- and the growth-directions of a ∼6 mm-thick wafer cut axially along the center of a CdZnTe ingot. We fabricated devices, selecting samples from the center slice outward in both directions, and then tested their response to incident X-rays. We employed, in concert, an automated IR transmission microscopic system and a highly collimated synchrotron X-ray source that allowed us to acquire and correlate comprehensive information on Te inclusions and other defects to assess the material factors limiting the performance of CdZnTe detectors.}, number={1}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Hossain, A. and Xu, L. and Bolotnikov, A.E. and Camarda, G.S. and Cui, Y. and Yang, G. and Kim, K.-H. and James, R.B.}, year={2011}, month={Oct}, pages={146–148} }
 @article{hossain_bolotnikov_camarda_gul_kim_cui_yang_xu_james_2011, title={Effect of Te inclusions in CdZnTe crystals at different temperatures}, volume={109}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.3549236}, DOI={10.1063/1.3549236}, abstractNote={CdZnTe crystals often exhibit nonuniformities due to the presence of Te inclusions and dislocations. High concentrations of such defects in these crystals generally entail severe charge-trapping, a major problem in ensuring the device’s satisfactory performance. In this study, we employed a high-intensity, high-spatial-resolution synchrotron x-ray beam as the ideal tool to generate charges by focusing it over the large Te inclusions, and then observing the carrier’s response at room- and at low-temperatures. A high spatial 5-μm resolution raster scan revealed the fine details of the presence of extended defects, like Te inclusions and dislocations in the CdZnTe crystals. A noticeable change was observed in the efficiency of electron charge collection at low temperature (1 °C), but it was hardly altered at room-temperature.}, number={4}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Hossain, A. and Bolotnikov, A. E. and Camarda, G. S. and Gul, R. and Kim, K.-H. and Cui, Y. and Yang, G. and Xu, L. and James, R. B.}, year={2011}, month={Feb}, pages={044504–044504-4} }
 @article{camarda_andreini_bolotnikov_cui_hossain_gul_kim_marchini_xu_yang_et al._2011, title={Effect of extended defects in planar and pixelated CdZnTe detectors}, volume={652}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2010.12.012}, DOI={10.1016/J.NIMA.2010.12.012}, abstractNote={We evaluated a spectroscopy-grade 15×15×7 mm3 CdZnTe (CZT) crystal with a high μτ-product, >10−2 cm2/V, but impaired by microscopic extended defects, such as walls of dislocations, low-angle and sub-grain boundaries, and Te inclusions. First, we evaluated a planar detector fabricated from this crystal using a Micro-scale X-ray Detector Mapping (MXDM) technique. Then, we fabricated from the same crystal a pixel detector to study local non-uniformities of the electric field. The measured X-ray response maps confirmed the presence of non-uniformities in the charge transport, and they showed that the global- and local-distortions of the internal E-field correlated to the extended defects and space-charge buildup on the side surfaces.}, number={1}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Camarda, G.S. and Andreini, K.W. and Bolotnikov, A.E. and Cui, Y. and Hossain, A. and Gul, R. and Kim, K.-H. and Marchini, L. and Xu, L. and Yang, G. and et al.}, year={2011}, month={Oct}, pages={170–173} }
 @article{yang_bolotnikov_camarda_cui_hossain_kim_gul_james_2011, title={Internal Electric Field Behavior of Cadmium Zinc Telluride Radiation Detectors Under High Carrier Injection}, volume={40}, ISSN={0361-5235 1543-186X}, url={http://dx.doi.org/10.1007/S11664-011-1656-3}, DOI={10.1007/S11664-011-1656-3}, abstractNote={The behavior of the internal electric field of nuclear-radiation detectors substantially affects detector performance. We investigated the distribution of the internal field in cadmium zinc telluride (CZT) detectors under high carrier injection. We noted the build-up of a space-charge region near the cathode that produces a built-in field opposing the applied field. Its presence entails the collapse of the electric field in the rest of the detector, other than the portion near the cathode. Such a space-charge region originates from serious hole trapping in CZT. The device’s operating temperature greatly affects the width of the space-charge region. With increasing temperature from 5°C to 35°C, its width expanded from about one-sixth to one-half of the total depth of the detector.}, number={8}, journal={Journal of Electronic Materials}, publisher={Springer Science and Business Media LLC}, author={Yang, G. and Bolotnikov, A. E. and Camarda, G. S. and Cui, Y. and Hossain, A. and Kim, K. H. and Gul, R. and James, R. B.}, year={2011}, month={May}, pages={1689–1692} }
 @article{yang_bolotnikov_cui_camarda_hossain_kim_gul_james_2011, title={Low-temperature spatially resolved micro-photoluminescence mapping in CdZnTe single crystals}, volume={98}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.3603930}, DOI={10.1063/1.3603930}, abstractNote={We utilized a low-temperature spatially resolved micro-photoluminescence mapping technique to investigate the spatial variation of photoluminescence- and electronic-defect states in areas of CdZnTe (CZT) single crystals containing structural-imperfections. Photoluminescence mapping of the donor-bound-exciton emission reveals an unexpected blue-shift of the CZT bandgap at Te inclusions, which indicates that for optical measurements the localized strain field needs to be considered for accurate calculation of Zn composition and energy levels near micro-scale defects. We observed that the line widths of the donor-bound-exciton peak and defect-related D band are broadened in regions with a high density of dislocations; in contrast, the donor-acceptor-pair peak is narrowed.}, number={26}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Yang, G. and Bolotnikov, A. E. and Cui, Y. and Camarda, G. S. and Hossain, A. and Kim, K. H. and Gul, R. and James, R. B.}, year={2011}, month={Jun}, pages={261901} }
 @article{kim_gul_carcelén_bolotinkov_carmarda_yang_hossain_cui_james_hong_et al._2010, title={Defect levels and thermomigration of Te precipitates in CdZnTe:Pb}, volume={312}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2009.11.069}, DOI={10.1016/j.jcrysgro.2009.11.069}, abstractNote={Semi-insulating Cd0.9Zn0.1Te:Pb crystals were grown by the vertical Bridgman method. Measurements of the current deep level transient spectroscopy (I-DLTS) revealed three trap levels in this material. Unlike other compensating dopants, CdZnTe:Pb samples do not show any Cd-vacancies defects and A-center levels. We subjected them to temperature-gradient annealing in Cd overpressure at 490–717 °C, and recorded an exponential relationship between the annihilation time of Te precipitates and the annealing temperature. The energy resolution of an annealed CdZnTe:Pb detector, tested using a 137Cs radioactive source, gave an energy resolution of 2.5%.}, number={6}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Kim, K.H. and Gul, R. and Carcelén, V. and Bolotinkov, A.E. and Carmarda, G.S. and Yang, G. and Hossain, A. and Cui, Y. and James, R.B. and Hong, J. and et al.}, year={2010}, month={Mar}, pages={781–784} }
 @article{kim_carcelén_bolotnikov_camarda_gul_hossain_yang_cui_james_2010, title={Effective Surface Passivation of CdMnTe Materials}, volume={39}, ISSN={0361-5235 1543-186X}, url={http://dx.doi.org/10.1007/S11664-010-1090-Y}, DOI={10.1007/S11664-010-1090-Y}, number={7}, journal={Journal of Electronic Materials}, publisher={Springer Science and Business Media LLC}, author={Kim, K.H. and Carcelén, V. and Bolotnikov, A.E. and Camarda, G.S. and Gul, R. and Hossain, A. and Yang, G. and Cui, Y. and James, R.B.}, year={2010}, month={Feb}, pages={1015–1018} }
 @article{hossain_bolotnikov_camarda_cui_yang_kim_gul_xu_james_2010, title={Extended defects in CdZnTe crystals: Effects on device performance}, volume={312}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2010.03.005}, DOI={10.1016/j.jcrysgro.2010.03.005}, abstractNote={We explored some unique defects in a batch of cadmium zinc telluride (CdZnTe) crystals, along with dislocations and Te-rich decorated features, revealed by chemical etching. We extensively investigated these distinctive imperfections in the crystals to identify their origin, dimensions, and distribution in the bulk material. We estimated that these features ranged from 50 to 500 μm in diameter, and their depth was about ∼300 μm. The density of these features ranged between 2×102 and 1×103 per cm3. We elaborated a model of them and projected their effect on charge collection and spectral response. In addition, we fabricated detectors with these defective crystals and acquired fine details of charge-transport phenomena over the detectors’ volume using a high-spatial resolution (25 μm) X-ray response mapping technique. We related the results to better understand the defects and their influence on the charge-transport properties of the devices. The role of the defects was identified by correlating their signatures with the findings from our theoretical model and our experimental data.}, number={11}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Hossain, A. and Bolotnikov, A.E. and Camarda, G.S. and Cui, Y. and Yang, G. and Kim, K-H. and Gul, R. and Xu, L. and James, R.B.}, year={2010}, month={May}, pages={1795–1799} }
 @article{yang_bolotnikov_li_camarda_cui_hossain_kim_carcelen_gul_james_2010, title={Investigation of Cadmium Manganese Telluride Crystals for Room-Temperature Radiation Detection}, volume={39}, ISSN={0361-5235 1543-186X}, url={http://dx.doi.org/10.1007/S11664-009-1050-6}, DOI={10.1007/S11664-009-1050-6}, number={7}, journal={Journal of Electronic Materials}, publisher={Springer Science and Business Media LLC}, author={Yang, G. and Bolotnikov, A. E. and Li, L. and Camarda, G. S. and Cui, Y. and Hossain, A. and Kim, K. and Carcelen, V. and Gul, R. and James, R. B.}, year={2010}, month={Jan}, pages={1053–1057} }
 @article{polack_hirt_sturgess_sferrazza_bolotnikov_babalola_camarda_cui_egarievwe_fochuk_et al._2010, title={Variation of electric shielding on virtual Frisch-grid detectors}, volume={621}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/j.nima.2010.05.035}, DOI={10.1016/j.nima.2010.05.035}, abstractNote={Because of the low mobility of holes, CdZnTe (CZT) detectors operate as electron-transport-only type devices whose particular geometrical parameters and contacts configurations are specially chosen to minimize the contribution of uncollected holes into the output signal amplitudes (induction effect). Several detector configurations have been proposed to address this problem. One of them employs a large geometrical aspect ratio, parallelepiped-shaped crystal with two planar contacts on the top and bottom surfaces (anode and cathode) and an additional shielding electrode placed on a crystal’s side to create the virtual Frisch-grid effect. We studied the effect of the shielding electrode length, as well as its location, on the responses of 6×6×15 mm3 virtual Frisch-grid detectors. We found that the length of the shielding electrode placed next to the anode can be reduced to 5 mm with no adverse effects on the device performance. Meanwhile, this allows for charge loss correction by reading the cathode signals.}, number={1-3}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Polack, J.K. and Hirt, M. and Sturgess, J. and Sferrazza, N.D. and Bolotnikov, A.E. and Babalola, S. and Camarda, G.S. and Cui, Y. and Egarievwe, S.U. and Fochuk, P.M. and et al.}, year={2010}, month={Sep}, pages={424–430} }
 @article{yang_bolotnikov_camarda_cui_hossain_yao_james_2009, title={Internal Electric Field Investigations of a Cadmium Zinc Telluride Detector Using Synchrotron X-ray Mapping and Pockels Effect Measurements}, volume={38}, ISSN={0361-5235 1543-186X}, url={http://dx.doi.org/10.1007/S11664-009-0799-Y}, DOI={10.1007/S11664-009-0799-Y}, number={8}, journal={Journal of Electronic Materials}, publisher={Springer Science and Business Media LLC}, author={Yang, G. and Bolotnikov, A. E. and Camarda, G. S. and Cui, Y. and Hossain, A. and Yao, H. W. and James, R. B.}, year={2009}, month={Apr}, pages={1563–1567} }
 @article{hossain_bolotnikov_camarda_cui_yang_james_2008, title={Defects in cadmium zinc telluride crystals revealed by etch-pit distributions}, volume={310}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2008.07.088}, DOI={10.1016/j.jcrysgro.2008.07.088}, abstractNote={We demonstrated the distribution of defects in cadmium zinc telluride (CZT) detectors by revealing etch pits on the surfaces with a chemical-etching method and Te inclusions in the bulk of the crystals. The dislocation networks observed from etch pits on the crystals' surfaces were traced down within the bulk by removing the material layer by layer, followed by sequential Nakagawa etching. We also identified the etch pits corresponding to Te inclusions, and correlated them with grain boundaries and dislocation lines.}, number={21}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Hossain, A. and Bolotnikov, A.E. and Camarda, G.S. and Cui, Y. and Yang, G. and James, R.B.}, year={2008}, month={Oct}, pages={4493–4498} }
 @article{yang_bolotnikov_cui_camarda_hossain_james_2008, title={Impurity gettering effect of Te inclusions in CdZnTe single crystals}, volume={311}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2008.09.201}, DOI={10.1016/j.jcrysgro.2008.09.201}, abstractNote={The local impurity distribution in Te inclusions of CdZnTe (CZT) crystal was investigated by the time-of-flight secondary ion mass spectrometry (Tof-SIMS) technique. Direct evidence of impurity gettering in Te inclusions has been observed for the first time. The impurity gettering in Te inclusions originated from the diffusion mechanism during crystal growth and segregation mechanism during crystal cooling. This phenomenon is meaningful, because it reveals how Te inclusions affect CZT properties and provides a possible approach to reduce the impurities in CZT by the way of removing Te inclusions.}, number={1}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Yang, G. and Bolotnikov, A.E. and Cui, Y. and Camarda, G.S. and Hossain, A. and James, R.B.}, year={2008}, month={Dec}, pages={99–102} }
 @article{yang_jie_wang_li_li_hua_2007, title={Correlation between Ingot Diameter and Crystal Properties of CdZnTe:In Grown by the Modified Bridgman Method}, volume={7}, ISSN={1528-7483 1528-7505}, url={http://dx.doi.org/10.1021/cg060464u}, DOI={10.1021/cg060464u}, abstractNote={The compound semiconductor CdZnTe:In is the most promising material for room temperature nuclear radiation detectors. Enlarging the diameter of CdZnTe:In ingot can improve the yield and reduce the production cost, which, however, affects the properties of CdZnTe:In to some extent. Recently, CdZnTe:In ingots of 30 mm and 60 mm diameter were grown by the modified vertical Bridgman method in our laboratory. The crystal properties of both ingots were compared according to etch pit density (EPD) of dislocation, X-ray rocking curve, IR transmission spectra, and photoluminescence (PL) spectra. For the CdZnTe:In ingot of 30 mm diameter, the EPD of dislocation was 2.1 × 104 cm-2, and was up to 1.9 × 105 cm-2 when the CdZnTe:In ingot diameter was enlarged to 60 mm. The full width at half-maximum (FWHM) of X-ray rocking also increased from 0.02014° to 0.02864° at the same time. The two phenomena imply that the crystalline quality of CdZnTe:In deteriorated with the enlarging of the ingot diameter. In addition, when t...}, number={2}, journal={Crystal Growth & Design}, publisher={American Chemical Society (ACS)}, author={Yang, Ge and Jie, Wanqi and Wang, Tao and Li, Guoqiang and Li, Wenwei and Hua, Hui}, year={2007}, month={Feb}, pages={435–438} }
 @article{zeng_jie_zha_wang_yang_2007, title={Effect of annealing on the residual stress and strain distribution in CdZnTe wafers}, volume={305}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2007.04.021}, DOI={10.1016/j.jcrysgro.2007.04.021}, abstractNote={The effect of annealing on residual stress and strain distribution in CdZnTe wafers was studied based using an X-ray diffraction (XRD) method. The results proved the effectiveness of annealing on the reduction of the residual stress and strain. By the means of transmission electron microscopy (TEM) and infrared (IR) transmission analyses, it was found that dislocation gliding, decreases in the size of the Te precipitates, dispersing of Te precipitates, composition homogenization, and point defects recombination contributed to a reduction of the residual stress and strain during annealing of the wafer. Additionally, the larger residual stress in CdZnTe wafers introduced bigger lattice misfits. Thus, for more the residual stress and strain in the CdZnTe wafer, the IR transmission will be lowered.}, number={1}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Zeng, Dongmei and Jie, Wanqi and Zha, Gangqiang and Wang, Tao and Yang, Ge}, year={2007}, month={Jul}, pages={50–54} }
 @article{wang_jie_zhang_yang_zeng_xu_ma_hua_he_2007, title={Study on the behaviors of impurities in cadmium zinc telluride}, volume={304}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2007.03.013}, DOI={10.1016/j.jcrysgro.2007.03.013}, abstractNote={Abstract Impurities in three cadmium zinc telluride (Cd 1− x Zn x Te or CZT) ingots grown by the modified vertical Bridgman (MVB) method were examined by using inductively coupled plasma mass spectrometry (ICP-MS). The distribution and segregation of impurities along the CZT ingots were found to vary with the concentration and the growth conditions. Photoluminescence (PL) and voltage–current measurements were performed to evaluate the effects of the impurities on the optical and electrical properties. The red shift of the ( D 0 , X ) and DAP positions and the broadening of the DAP band in PL spectrum were observed in the high-impurity CZT ingot. The voltage–current measurement shows a higher resistivity when the impurity concentration was increased. The above results imply that the high-impurity CZT ingot was highly compensated.}, number={2}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Wang, Tao and Jie, Wanqi and Zhang, Jijun and Yang, Ge and Zeng, Dongmei and Xu, Yadong and Ma, Shuying and Hua, Hui and He, Ke}, year={2007}, month={Jun}, pages={313–316} }
 @article{yang_jie_jhang_wang_li_hua_2006, title={Effects of two-step annealing on properties of Cd1-xZnxTe single crystals}, volume={16}, ISSN={1003-6326}, url={http://dx.doi.org/10.1016/S1003-6326(06)60169-6}, DOI={10.1016/S1003-6326(06)60169-6}, abstractNote={The Cd1-xZnxTe(CZT) single crystals were annealed by a two-step method including a vapor-environment step and a liquid-environment step in sequence. The effects of annealing on the properties of CZT were analyzed in detail. IR transmission measurement results show that IR transmission of CZT is improved dramatically after annealing. X-ray rocking curves indicate that the annealing treatment ameliorates crystal quality obviously, which is ascribed to the release of residual stress and the reduction of point defects. Photoluminescence(PL) spectra reveal that the full width at half maximum(FWHM) of the donor-bound exciton (D0,X) peak is reduced obviously, and the free exciton emission is weakened after annealing. Meanwhile, the intensity of the donor-acceptor pair(DAP) peak decreases to a great degree, which implies that the impurities are removed from CZT wafers. In addition, the deep defect-related emission band Dcomplex disappears after annealing, which mean that Cd vacancies are well-compensated. The results confirm that the two-step annealing is an effective approach to improve the qualities of CZT single crystals.}, journal={Transactions of Nonferrous Metals Society of China}, publisher={Elsevier BV}, author={Yang, Ge and Jie, Wan Qi and Jhang, Qun Ying and Wang, Tao and Li, Qiang and Hua, Hui}, year={2006}, month={Jun}, pages={s174–s177} }
 @article{li_jie_fu_yang_zha_wang_bai_2006, title={Electrical properties and electrical field in depletion layer for CZT crystals}, volume={16}, ISSN={1003-6326}, url={http://dx.doi.org/10.1016/S1003-6326(06)60146-5}, DOI={10.1016/S1003-6326(06)60146-5}, abstractNote={Current—voltage (I—V) and capacitance—voltage (C—V) characteristics of Au/p-CZT contacts with different surface treatments on cadmium zinc telluride (CZT) wafer's surface were measured with Agilent 4339B high resistance meter and Agilent 4294A precision impedance analyzer, respectively. The Schottky barrier height was 0.85±0.05, 0.96±0.05 eV for non-passivated and passivated CZT crystals by I—V measurement. By C—V measurement, the Schottky barrier height was 1.39±0.05, 1.51±0.05 eV for non-passivated and passivated CZT crystals. The results show that the passivation treatment can increase the barrier height of the Au/p-CZT contact and decrease the leakage current. The main reason is that the higher barrier height of Au/p-CZT contacts can decrease the possibility for electrons to pass through the native TeO2 film. Most of the applied voltage appears on the depleted layer and there is only a negligible voltage drops across the nearly undepleted region. Furthermore, the electric field in the depleted layer is not uniform and can be calculated by the depletion approximation. The maximum electric field of CZT crystals is Eml=133 V/cm at x=0 for non-passivated CZT crystal and Em2=55 V/cm for passivated CZT crystal, respectively.}, journal={Transactions of Nonferrous Metals Society of China}, publisher={Elsevier BV}, author={Li, Qiang and Jie, Wan Qi and Fu, Li and Yang, Ge and Zha, Gang Qiang and Wang, Tao and Bai, Xu Xu}, year={2006}, month={Jun}, pages={s75–s78} }
 @article{li_jie_fu_wang_yang_bai_zha_2006, title={Optical and electrical properties of indium-doped Cd0.9Zn0.1Te crystal}, volume={295}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2006.07.030}, DOI={10.1016/j.jcrysgro.2006.07.030}, abstractNote={The indium-doped CdZnTe crystal was characterized by PL spectra at 10 K and IR transmission spectra, as well as its current–voltage behavior at room temperature. The results showed that indium atoms substituted for the Cd vacancy and produced ionized donors [InCd]+, i.e. indium doping element recombined with [Vcd]2− and formed the singly negative defect complex A-center [InCd+VCd2-]- and the neutral ones [2InCd+VCd2-]0 and [Incd+(InCd+VCd2-)-]0. Indium doping also increased the IR absorption of the CdZnTe crystal due to the lattice absorption and free-carrier absorption. Meanwhile, indium doping increased the electrical resistivity and decreased the leakage current of CdZnTe crystals remarkably.}, number={2}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Li, Qiang and Jie, Wanqi and Fu, Li and Wang, Tao and Yang, Ge and Bai, Xuxu and Zha, Gangqiang}, year={2006}, month={Oct}, pages={124–128} }
 @article{yang_jie_2006, title={Photoluminescence analysis of Cd1−xZnxTe single crystals annealed by a two-step method}, volume={294}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2006.06.016}, DOI={10.1016/j.jcrysgro.2006.06.016}, abstractNote={Abstract Cd 1− x Zn x Te (CZT) single crystals were annealed by a two-step method, including a vapor-environment step and a liquid-environment step in sequence. Photoluminescence spectra were used to investigate the effects of annealing on the properties of CZT. After annealing the full width at half maximum of the donor-bound exciton (D 0 ,X) peak was reduced, and the free-exciton emission was weakened. Meanwhile, the intensity of the donor–acceptor pair peak was greatly decreased. In addition, the deep defect-related emission band D complex disappeared after the annealing, which was distinct for as-grown CZT wafers. The investigation confirms that the two-step annealing can compensate for cadmium vacancies and possibly reduce the impurities from CZT wafers.}, number={2}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Yang, Ge and Jie, Wanqi}, year={2006}, month={Sep}, pages={250–253} }
 @article{zha_jie_li_zeng_yang_bai_wang_zhang_xu_2006, title={The study on the surface state of CdZnTe (110) surface}, volume={252}, ISSN={0169-4332}, url={http://dx.doi.org/10.1016/j.apsusc.2005.11.061}, DOI={10.1016/j.apsusc.2005.11.061}, abstractNote={Angle-resolved photoemission spectroscopy (ARPES) was used to characterize the surface state of clean CdZnTe (1 1 0) surface. The surface state of CdZnTe with the peak at 0.9 eV below the Fermi level is identified. Meanwhile, Photoluminescence (PL) spectrum confirmed that there existed a surface trap state which introduced a deep-level peak at 1.510 eV. The surface trap states can be decreased by aging in dry-air. The surface leakage current was measured also by I–V measurements. After aging, the leakage current was decreased remarkably, which suggested that the aging treatment is an effective method to decrease the surface trap state.}, number={24}, journal={Applied Surface Science}, publisher={Elsevier BV}, author={Zha, Gangqiang and Jie, Wanqi and Li, Qiang and Zeng, Dongmei and Yang, Ge and Bai, Xuxu and Wang, Tao and Zhang, Wenhua and Xu, Faqiang}, year={2006}, month={Oct}, pages={8421–8423} }
 @article{yang_jie_li_wang_li_hua_2005, title={Effects of In doping on the properties of CdZnTe single crystals}, volume={283}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2005.06.035}, DOI={10.1016/j.jcrysgro.2005.06.035}, abstractNote={An intrinsic CdZnTe ingot and an Indium (In) doped CdZnTe:In ingot were grown by the modified Bridgman (MB) method, respectively. The effects of In-doping on the properties of CdZnTe single crystals have been analyzed in detail. Leakage current–bias voltage (I–V) measurement shows that the resistivity of CdZnTe increases three orders after In is introduced into the crystal, because cadmium (Cd) vacancies are effectively compensated by In. The leakage current in CdZnTe:In is stabilized more quickly compared with that in CdZnTe, revealed by leakage current–time (I-t) measurement. IR transmission spectra of both ingots indicate that In-doping results in remarkable reduction of the IR transmission of CdZnTe crystals. Photoluminescence (PL) measurement shows that a new deep-level emission appears, due to an In-related complex, and the acceptor-bound (A0,X) peak disappears in the case of CdZnTe:In. It confirms that Cd vacancies are completely compensated by the In-related complex, which is consistent with the result of the I–V measurement. In addition, the intensity of the donor–acceptor pair recombination (D, A) peak becomes stronger after In is introduced. It indicates that there still exists excess In in the crystal after Cd vacancies are completely compensated.}, number={3-4}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Yang, Ge and Jie, Wanqi and Li, Qiang and Wang, Tao and Li, Guoqiang and Hua, Hui}, year={2005}, month={Oct}, pages={431–437} }
 @article{yang_jie_li_2005, title={Effects of annealing on the properties of Au–Cd0.9Zn0.1Te contacts}, volume={123}, ISSN={0921-5107}, url={http://dx.doi.org/10.1016/j.mseb.2005.07.024}, DOI={10.1016/j.mseb.2005.07.024}, abstractNote={Au–Cd0.9Zn0.1Te contacts were annealed for 10 min at 100, 200 and 300 °C, respectively. The effects of annealing have been analyzed with photoluminescence (PL) spectra, leakage current-bias voltage (I–V) characteristic and leakage current–time (I–t) characteristic. PL spectra indicate that there are more Au-related complexes and Cd vacancies (Zn vacancies) produced in Au–Cd0.9Zn0.1Te contacts during the annealing. These complexes and vacancies are responsible for the decrease of leakage current, which is revealed by I–V measurement, because they can trap free charge and improve the recombination rate of charge effectively. The I–V measurement also shows that the ohmic characteristic of Au–Cd0.9Zn0.1Te contacts is improved obviously by the annealing at 100 and 200 °C and deteriorated seriously by the annealing at 300 °C. In addition, I–t curves suggest that annealing can improve the stability of leakage current remarkably.}, number={2}, journal={Materials Science and Engineering: B}, publisher={Elsevier BV}, author={Yang, Ge and Jie, Wanqi and Li, Qiang}, year={2005}, month={Nov}, pages={172–175} }
 @article{li_jie_yang_wang_2004, title={Behaviors of impurities in Cd0.85Zn0.15Te crystals grown by vertical Bridgman method}, volume={113}, ISSN={0921-5107}, url={http://dx.doi.org/10.1016/j.mseb.2004.05.006}, DOI={10.1016/j.mseb.2004.05.006}, abstractNote={The distribution of impurities Li, Na, Mg, Al, S, Cl, K, Cu, In, Ga and Ag in Cd0.85Zn0.15Te crystal ingots grown by vertical Bridgman method has been investigated using the inductively coupled plasma mass spectrometry (ICP/MS). It is found that the segregation coefficients of Al, S, In and Ga are larger than unit, which leads to their enrichment in the first-to-freeze portion of ingots, while the segregation coefficients of Li, Na, Mg, Cl, K, Cu and Ag are less than unit, which leads to their enrichment in the last-to-freeze portion of ingots. Resistivity measurements reveal that Mg, Al, S, Cl, In and Ga are positive to increase the resistivity of Cd0.85Zn0.15Te, while Li, Na, K, Cu, and Ag are negative. Infrared (IR) transmission measurements and Hall measurements indicate that the free carrier absorption within the both impurity enriching portions decreases IR transmission and causes a decrease in IR transmission with the decrease of wavenumber. After an annealing processing, the concentration of all the impurities is highly reduced and the crystal properties are remarkably improved.}, number={1}, journal={Materials Science and Engineering: B}, publisher={Elsevier BV}, author={Li, Guoqiang and Jie, Wanqi and Yang, Ge and Wang, Tao}, year={2004}, month={Oct}, pages={7–12} }
 @article{li_jie_gu_yang_wang_zhang_2004, title={Growth of In doped CdZnTe by vertical Bridgman method and the effect of In on the crystal properties}, volume={265}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2003.12.079}, DOI={10.1016/j.jcrysgro.2003.12.079}, abstractNote={An Indium (In) doped Cd0.9Zn0.1Te (CdZnTe:In) ingot was grown by vertical Bridgman method. The distribution of In in the ingot was analyzed. It was evaluated that the segregation coefficient of In in CdZnTe during the growth was 1.3, which caused a higher In concentration in the initial part of CdZnTe:In ingot and a lower In concentration in the final part. In was also enriched at the grain boundaries but homogeneously distributed inside the grains in the as-grown crystal. Photoluminescence spectra indicated that In had two states existing in the CdZnTe:In ingot. One was interstitial neutral In and the other was substitutional ion In+. The two states led to the two donor levels at 0.12 and 0.04 eV in CdZnTe:In band construction, respectively. IR transmission measurements exhibited that CdZnTe:In was almost opaque to IR emission when the wavenumber was larger than 1000 cm−1, then was 24% transparent when the wavenumber was decreased to lower than 1000 cm−1. This phenomenon also confirmed the existence of the donor level of 0.12 eV demonstrated by the PL spectra. Resistivity measurements revealed that CdZnTe:In obtained three orders higher resistivity than CdZnTe. It meant that doping of In into CdZnTe could improve the crystal properties.}, number={1-2}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Li, Guoqiang and Jie, Wanqi and Gu, Zhi and Yang, Ge and Wang, Tao and Zhang, Jijun}, year={2004}, month={Apr}, pages={159–164} }
 @article{li_jie_wang_yang_2004, title={Impurities in CdZnTe crystal grown by vertical Bridgman method}, volume={534}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2004.06.135}, DOI={10.1016/J.NIMA.2004.06.135}, abstractNote={The impurity segregation in CdZnTe grown by vertical Bridgman method and its corresponding effects on the crystal optical and electrical properties have been studied in detail. Inductively coupled plasma mass spectrometry reveals that impurities Al and Ga with segregation coefficient larger than one centralize in the first-to-freeze portion of the ingot, while impurities Li, Na, Mn, and Cu with segregation coefficient less than one enrich in the last-to-freeze portion of the ingot. At the same time, all impurities enrich in the grain boundaries. Hall measurement indicates that there exists an approximate linear monotonously increasing relationship between the free-carrier density and the sum of all the impurities concentration, which leads to an increase in the infrared transmission with the increase of wave number within the impurity enriching portions caused by the free carrier absorption. It is also found that the resistivity decreases with the concentration of Li, Na, and Cu, but increases with the concentration of Al, Mn, and Ga. An annealing processing is adopted to extract the impurities and therefore improve the crystal properties.}, number={3}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Li, Guoqiang and Jie, Wanqi and Wang, Tao and Yang, Ge}, year={2004}, month={Dec}, pages={511–517} }