@article{grenko_ebert_reynolds_duscher_barlage_johnson_preble_paskova_evans_2010, title={Optimization of homoepitaxially grown AlGaN/GaN heterostructures}, volume={207}, ISSN={["1862-6300"]}, DOI={10.1002/pssa.200925508}, abstractNote={AbstractWe report on the growth of Al0.25Ga0.75N/GaN heterostructures on low dislocation density semi‐insulating c‐axis GaN substrates by metalorganic vapor phase epitaxy (MOVPE). A room temperature (RT) Hall mobility (µRT) up to 2065 cm2 V−1 s−1 at sheet density (ns) of 8.25 × 1012 cm−2 has been measured. This work compliments prior studies in which we observed a buffer‐induced modulation of the RT two‐dimensional electron gas (2DEG) ns and µRT by varying the GaN buffer layer thickness. Here, we focus on the optimization of the heterostructure 2DEG properties by elimination of silicon doping in the Al0.25Ga0.75N barrier and unintentional Al in the not‐intentionally doped (n.i.d.) GaN buffer layer. The 15% improvement in µRT and ns relative to previous results is consistent with those predicted by Poisson solver calculations. Use of thick GaN buffers has minimized the theoretical mobility reduction based on intersubband scattering and has enabled us to determine the 2DEG sheet density associated with the polarization field ($n_{{\rm s}}^{{\rm polar}} $) to be ∼5 × 1012 cm−2.}, number={10}, journal={PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE}, author={Grenko, J. A. and Ebert, C. W. and Reynolds, C. L., Jr. and Duscher, G. J. and Barlage, D. W. and Johnson, M. A. L. and Preble, E. A. and Paskova, T. and Evans, K. R.}, year={2010}, month={Oct}, pages={2292–2299} } @article{biggerstaff_reynolds_zheleva_lelis_habersat_haney_ryu_agarwal_duscher_2009, title={Relationship between 4H-SiC/SiO2 transition layer thickness and mobility}, volume={95}, ISSN={["0003-6951"]}, DOI={10.1063/1.3144272}, abstractNote={The interfacial region between silicon carbide (SiC) and its native oxide contains a high density of interfacial traps, which is considered a major problem leading to a lower mobility that has hindered SiC metal oxide semiconductor field effect transistors from reaching their theoretical expectations. We investigate the microstructure and chemistry of the 4H-SiC∕SiO2 interface due to variations in nitric oxide annealing and aluminum implantation using Z-contrast imaging and electron energy loss spectroscopy. A transition layer with a carbon to silicon ratio greater than 1 is consistently observed on the SiC side of the interface in each of these samples, and the width of this transition layer is found to be inversely related to the effective channel mobility measured on fabricated devices.}, number={3}, journal={APPLIED PHYSICS LETTERS}, author={Biggerstaff, T. L. and Reynolds, C. L., Jr. and Zheleva, T. and Lelis, A. and Habersat, D. and Haney, S. and Ryu, S. -H. and Agarwal, A. and Duscher, G.}, year={2009}, month={Jul} } @article{pei_duscher_steen_pichler_ssel_napolitani_de salvador_piro_terrasi_severac_et al._2008, title={Detailed arsenic concentration profiles at Si/SiO2 interfaces}, volume={104}, number={4}, journal={Journal of Applied Physics}, author={Pei, L. and Duscher, G. and Steen, C. and Pichler, P. and Ssel, H. R. and Napolitani, E. and De Salvador, D. and Piro, A. M. and Terrasi, A. T. and Severac, F. and et al.}, year={2008} } @article{liu_collazo_mita_sitar_pennycook_duscher_2008, title={Direct Observation of Inversion Domain Boundaries of GaN onc-Sapphire at Sub-ångstrom Resolution}, volume={20}, ISSN={0935-9648 1521-4095}, url={http://dx.doi.org/10.1002/adma.200702522}, DOI={10.1002/adma.200702522}, abstractNote={Wide-bandgap III–nitrides have seen enormous success in modern electronic, optoelectronic, and even spintronic devices. Recently, interest has grown in manipulating the crystal polarity of GaN having a wurtzite structure, which provides a new degree of freedom for investigating III–nitrides and their novel devices. These studies include work on the inversion domain boundaries (IDBs) of GaN, which separate adjacent domains of different polarity. Ten years ago, Northrup et al. performed first-principles calculations of domain-boundary energies and proposed the structure shown in Figure 1, based on its very low energy (25 meV A ). Since then, no direct, indisputable test has been carried out to determine the exact boundary structure. At the same time, many unique properties have been observed at the IDBs. Among these is the remarkable effect, observed by Stutzmann et al. that the IDB can act as a rectifying junction when biased by two electrodes placed on adjacent Gaand N-face regions. The boundary between two adjacent domains with different polarity has been shown to be a very efficient radiative recombination center, which may have potential application for novel light-emitting devices. Meanwhile, it was found that the rectifying behavior of the IDBs can be explained by ab initio density functional calculations, assuming the IDBs have a structure as shown in Figure 1 (where a thin AlN layer is used to invert the polarity of GaN). However, the IDB structure has never been determined directly and their real structure remains unconfirmed. Here we show that we have determined directly the IDB structure, including the determination of GaN polarity, by aberration-corrected scanning transmission electron microscopy (STEM) at sub-Angstrom}, number={11}, journal={Advanced Materials}, publisher={Wiley}, author={Liu, Fude and Collazo, Ramon and Mita, Seiji and Sitar, Zlatko and Pennycook, Stephen J. and Duscher, Gerd}, year={2008}, month={Jun}, pages={2162–2165} } @article{leonard_cerruti_duscher_franzen_2008, title={Interfacial and solvent effects govern the formation of tris(dibenzylidenacetone)dipalladium(0) microstructures}, volume={24}, ISSN={["0743-7463"]}, DOI={10.1021/la801039j}, abstractNote={Organometallic palladium adducts have application as catalysts and as precursors for nanoparticle synthesis. Herein, we study the spontaneous formation of molecular crystals of the organometallic reagent tris(dibenzylidenacetone)dipalladium(0) (Pd(2)(DBA)(3)) in THF/H(2)O binary solvent systems. We report structural and chemical characterization of the resulting diverse structures with shapes including hexagonal platelets, rods, cubes, and stars. Optical microscopy, transmission electron microscopy, scanning electron microscopy, and energy-dispersive spectroscopy were used to determine representative structures and corresponding compositions when formed either in a binary solution or upon evaporation on a surface. The difference in Pd(2)(DBA)(3) particle morphology was attributed to differences in the surface tension of growing crystalline faces. The formation of a majority of rods or hexagonal platelets in solution was shown to be determined by the ratio of THF to H(2)O in the solvent, whereas supersaturation effects and interfacial surface tension played a major role in creating the shape of particles formed upon evaporation of Pd(2)(DBA)(3) droplets on a surface.}, number={15}, journal={LANGMUIR}, author={Leonard, Donovan N. and Cerruti, Marta and Duscher, Gerd and Franzen, Stefan}, year={2008}, month={Aug}, pages={7803–7809} } @article{darling_reynolds_leonard_duscher_scattergood_koch_2008, title={Self-assembled three-dimensional Cu-Ge nanoweb composite}, volume={19}, ISSN={["1361-6528"]}, DOI={10.1088/0957-4484/19/13/135603}, abstractNote={The inexpensive combination of cryogenically milled Cu3Ge powders sonochemically processed in a standard ultrasonic cleaner has led to the prototype of a heretofore undescribed class of material. This prototype is a nanostructured composite composed of 4.5 nm diameter Cu nanocrystals embedded in a three-dimensional (3D) amorphous CuGeO3 polyhedron web matrix. The diameters of the wires comprising the matrix are typically 5–15 nm. Complete structural and compositional characterization is reported to provide additional insight and firm designation on the observation of this previously undescribed class of material. The large surface to volume ratio of these nanoweb composites may offer unique advantages based on altered optical or electronic and magnetic properties. For example, quantum confinement of the Cu dots in the amorphous 3D nanowebs is possible. Nanostructures in general have altered properties compared to those of bulk materials and the same is expected in nanostructured composites.}, number={13}, journal={NANOTECHNOLOGY}, author={Darling, Kris A. and Reynolds, C. Lewis, Jr. and Leonard, Donovan N. and Duscher, Gerd and Scattergood, Ronald O. and Koch, Carl C.}, year={2008}, month={Apr} } @article{zheleva_lelis_duscher_liu_levin_das_2008, title={Transition layers at the SiO2/SiC interface}, volume={93}, number={2}, journal={Applied Physics Letters}, author={Zheleva, T. and Lelis, A. and Duscher, G. and Liu, F. and Levin, I. and Das, M.}, year={2008} } @article{steen_martinez-limia_pichler_ryssel_paul_lerch_pei_duscher_severac_cristiano_et al._2008, title={stee Distribution and segregation of arsenic at the SiO2/Si interface}, volume={104}, number={2}, journal={Journal of Applied Physics}, author={Steen, C. and Martinez-Limia, A. and Pichler, P. and Ryssel, H. and Paul, S. and Lerch, W. and Pei, L. and Duscher, G. and Severac, F. and Cristiano, F. and et al.}, year={2008} } @article{liu_duscher_2007, title={Chemical composition changes across the interface of amorphous LaScO3 on Si (001)}, volume={91}, number={15}, journal={Applied Physics Letters}, author={Liu, F. and Duscher, G.}, year={2007} } @article{zhao_duscher_rozgonyi_zikry_chopra_ozturk_2007, title={Quantitative nanoscale local strain profiling in embedded SiGe metal-oxide-semiconductor structures}, volume={90}, ISSN={["1077-3118"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34248361149&partnerID=MN8TOARS}, DOI={10.1063/1.2738188}, abstractNote={Mechanical strain by strain engineering has been widely used in Si metal-oxide-semiconductor field effect transistors. Experimental convergent beam electron diffraction (CBED) strain measurements and finite element calculations to quantitatively correlate the strain in the transmission electron microscope (TEM) sample with the actual device. It was found that the magnitude of the longitudinal strain, εx, along the channel direction, is about 20% higher in the TEM sample than in the real device. This combined approach can be used to explain data from other CBED studies of strained Si devices.}, number={19}, journal={APPLIED PHYSICS LETTERS}, author={Zhao, W. and Duscher, G. and Rozgonyi, G. and Zikry, M. A. and Chopra, S. and Ozturk, M. C.}, year={2007}, month={May} } @article{liu_collazo_mita_sitar_duscher_pennycook_2007, title={The mechanism for polarity inversion of GaN via a thin AlN layer: Direct experimental evidence}, volume={91}, ISSN={["1077-3118"]}, DOI={10.1063/1.2815748}, abstractNote={Lateral-polarity heterostructures of GaN on c sapphire were prepared by deposition and patterning of a thin low-temperature AlN nucleation layer. Adjacent macroscopic domains were found to have opposite polarity; domains grown on the AlN nucleation layer were Ga polar while those grown on the nitrided sapphire were N polar, as confirmed by convergent-beam electron diffraction and Z-contrast images. We directly determined the atomic interface structure between the AlN and c sapphire with an aberration-corrected scanning transmission electron microscope at ∼1.0Å resolution. This is the direct experimental evidence for the origin of the polarity control in III nitrides. This understanding is an important step toward manipulating polarity in these semiconductors.}, number={20}, journal={APPLIED PHYSICS LETTERS}, author={Liu, Fude and Collazo, Ramon and Mita, Seiji and Sitar, Zlatko and Duscher, Gerd and Pennycook, Stephen J.}, year={2007}, month={Nov} } @article{franzen_cerruti_leonard_duscher_2007, title={The role of selection pressure in RNA-mediated evolutionary materials synthesis}, volume={129}, ISSN={["0002-7863"]}, DOI={10.1021/ja076054r}, abstractNote={Evolutionary materials synthesis is a provocative concept that has the potential for the discovery of novel compounds ranging from drugs to inorganic materials. RNA-mediated evolutionary materials synthesis requires aqueous solvent of moderate ionic strength, water-soluble precursors, and an appropriately designed selection pressure. Throughout the selection process, the RNA must be folded, stable, and accessible once it has bound to a target, catalyzed a chemical reaction, or templated formation of a structure. Subsequently, the RNA must be accessible to permit reverse transcriptase to create DNA copies for amplification. A well-designed selection will generate RNAs that can favor growth of a particular crystal habit or catalyze a specific reaction pathway. In this study we rigorously test the assumptions, procedures, and results of the only published example of an RNA-mediated evolutionary materials synthesis. The proof that a particular RNA sequence is responsible for a novel material synthesis must be established by control experiments as outlined in the present study. Furthermore, the product of nanoscale synthesis must be studied using state-of-the-art characterization methods to determine that selection pressure is exerted according to design. Herein, we demonstrate the use of advanced electron microscopy to determine chemical composition and structure as a critical step in analysis of the success of a selection. We conclude that RNA selections should not be carried out in binary solvent systems, such as tetrahydrofuran (THF) and water. A specific example, which is not consistent with rigorous selection of functional RNAs or RNA cognates, is provided by the precipitation of the water-insoluble precursor, tris(dibenzylideneacetone) dipalladium(0) Pd2(DBA)3.}, number={49}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Franzen, Stefan and Cerruti, Marta and Leonard, Donovan N. and Duscher, Gerd}, year={2007}, month={Dec}, pages={15340–15346} } @article{liu_duscher_2007, title={Thermal annealing effect on the interface structure of high-kappa LaScO3 on silicon}, volume={91}, number={15}, journal={Applied Physics Letters}, author={Liu, F. and Duscher, G.}, year={2007} } @article{liu_collazo_mita_sitar_duscher_2008, title={Three-dimensional geometry of nanometer-scale AlN pits: A new template for quantum dots?}, volume={20}, DOI={10.1002/adma.200701288}, abstractNote={The exact 3D geometry of nanometer-scale AlN pits is determined by Z-contrast imaging. The figure shows the 3D geometry of an AlN nano-pit and its corresponding GaN quantum dot. An atomic-resolution Z-contrast image is displayed in false color to clearly show the Z-contrast of the image, while the other panel displays a schematic 3D view.}, number={1}, journal={Advanced Materials}, author={Liu, F. D. and Collazo, Ramon and Mita, S. and Sitar, Z. and Duscher, G.}, year={2008}, pages={134-} } @article{saripalli_pei_biggerstaff_ramachandran_duscher_johnson_zeng_dandu_jin_barlage_2007, title={Transmission electron microscopy studies of regrown GaN Ohmic contacts on patterned substrates for metal oxide semiconductor field effect transistor applications}, volume={90}, ISSN={["1077-3118"]}, DOI={10.1063/1.2741123}, abstractNote={Contact selected area regrowth of GaN was performed by metal organic chemical vapor deposition using a silicon nitride dielectric hard mask to define plasma etched recesses and to define source-drain regions. A low temperature regrowth process at 750–850°C was adopted to limit lateral overgrowth. High resolution electron microscopy images and selected area diffraction confirmed the regrowth selectivity and revealed that the low temperature regrown GaN is epitaxial and has a wurtzite crystal structure. I-V characteristics of the fabricated metal oxidesemiconductor field effect transistor show enhancement mode operation.}, number={20}, journal={APPLIED PHYSICS LETTERS}, author={Saripalli, Y. N. and Pei, L. and Biggerstaff, T. and Ramachandran, S. and Duscher, G. J. and Johnson, M. A. L. and Zeng, C. and Dandu, K. and Jin, Y. and Barlage, D. W.}, year={2007}, month={May} } @article{rajulapati_scattergood_murty_duscher_koch_2006, title={Effect of Pb on the mechanical properties of nanocrystalline Al}, volume={55}, ISSN={["1359-6462"]}, DOI={10.1016/j.scriptamat.2006.03.051}, abstractNote={Nanocrystalline (nc) Al–Pb two phase mixtures of different Pb concentrations were made by two different routes using high energy ball milling. The microhardness measurements show a softening in nc Al–Pb composites with the increase in Pb content, contradicting the previous results reported in the literature. We conclude that interaction of Pb atoms with nanocrystalline Al grain boundaries is responsible for the softening of the nc Al matrix observed in the current study.}, number={2}, journal={SCRIPTA MATERIALIA}, author={Rajulapati, Koteswararao V. and Scattergood, Ronald O. and Murty, Korukonda L. and Duscher, Gerd and Koch, Carl C.}, year={2006}, month={Jul}, pages={155–158} } @article{cerruti_sauthier_leonard_liu_duscher_feldheim_franzen_2006, title={Gold and silica-coated gold nanoparticles as thermographic labels for DNA detection}, volume={78}, ISSN={["1520-6882"]}, DOI={10.1021/ac0600555}, abstractNote={The infrared emissivity of Au and silica-coated Au nanoparticles (Au NPs) deposited on indium tin oxide substrates was investigated. NPs were irradiated with laser light at a frequency close to the Au plasmon resonance band, and the blackbody radiation emitted as a result was monitored with an IR camera equipped with an InAs array detector. The differences in temperature before and after laser irradiation were recorded (T-jumps) and were found to be directly proportional to the number of particles present on the slide and to the laser power used in the experiment. Coating Au NPs with silica increased the measured T-jumps 2-5 times, depending on the thickness of the silica shell. This was in agreement with the observation that silica has a much higher IR emissivity than Au. Both Au and silica-coated Au NPs were then tested as labels for thermographic DNA detection. Target DNA concentrations as low as 100 pM were recorded when Au NPs were used as labels and as low as 10 pM when silica-coated Au NPs were used.}, number={10}, journal={ANALYTICAL CHEMISTRY}, author={Cerruti, Marta G. and Sauthier, Marc and Leonard, Donovan and Liu, Dage and Duscher, Gerard and Feldheim, Daniel L. and Franzen, Stefan}, year={2006}, month={May}, pages={3282–3288} } @article{rhodes_franzen_maria_losego_leonard_laughlin_duscher_weibel_2006, title={Surface plasmon resonance in conducting metal oxides}, volume={100}, ISSN={["1089-7550"]}, DOI={10.1063/1.2222070}, abstractNote={We report the initial observation of surface plasmon resonance (SPR) in a conducting metal oxide thin film. The SPR phenomenon has been observed by attenuated total reflection of near-infrared radiation and is in agreement with electron energy loss spectroscopy measurements. To date, only metals are known to exhibit surface plasmon resonance and only noble metals have practical application. According to theory SPR should be observable in any conductor. This theoretical prediction is verified in the present study. The compositions of many conducting metal oxides are systematically variable, suggesting a significant advance in thin film characterization and innovative possibilities for versatile and sensitive chemical sensing applications.}, number={5}, journal={JOURNAL OF APPLIED PHYSICS}, author={Rhodes, Crissy and Franzen, Stefan and Maria, Jon-Paul and Losego, Mark and Leonard, Donovan N. and Laughlin, Brian and Duscher, Gerd and Weibel, Stephen}, year={2006}, month={Sep} } @article{stoddard_duscher_windl_rozgonyi_2005, title={A new understanding of near-threshold damage for 200 keV irradiation in silicon}, volume={40}, ISSN={["1573-4803"]}, DOI={10.1007/s10853-005-1059-z}, number={14}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Stoddard, N and Duscher, G and Windl, W and Rozgonyi, G}, year={2005}, month={Jul}, pages={3639–3650} } @article{stoddard_pichler_duscher_windl_2005, title={Ab initio identification of the nitrogen diffusion mechanism in silicon}, volume={95}, number={2}, journal={Physical Review Letters}, author={Stoddard, N. and Pichler, P. and Duscher, G. and Windl, W.}, year={2005} } @article{wang_shutthanandan_zhang_thevuthasan_duscher_2005, title={Atomic resolution imaging of Au nanocluster dispersed in TiO2, SrTiO3, and MgO}, volume={88}, ISSN={["0002-7820"]}, DOI={10.1111/j.1551-2916.2005.00579.x}, abstractNote={ Gold nanoclusters dispersed in single crystal TiO2, MgO, and SrTiO3 have been prepared by ion implantation at 300–975 K and subsequent annealing at 1275 K for 10 h. High‐resolution transmission electron microscopy and high‐angle annular dark field (HAADF) imaging in aberration corrected scanning transmission electron microscope (STEM) have been used to characterize the microstructure of the gold nanoclusters dispersed materials. STEM‐HAADF imaging with atomic resolution has directly revealed for all three materials that Au atoms partially occupy cation lattice positions. Cavities up to several tens of nanometers were observed in MgO and SrTiO3. The cavities and gold clusters are spatially associated in MgO and SrTiO3, indicating a strong interaction between the Au cluster and cavities. For MgO and SrTiO3, the faceting planes appear to be the same for both nanometer‐sized cavity and the Au cluster, demonstrating that both the surface energy and the interfacial energy between Au cluster and the matrix are lowest on these planes. }, number={11}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Wang, CM and Shutthanandan, V and Zhang, Y and Thevuthasan, S and Duscher, G}, year={2005}, month={Nov}, pages={3184–3191} } @article{wang_shutthanandan_thevuthasan_duscher_2005, title={Direct imaging of quantum antidots in MgO dispersed with Au nanoclusters}, volume={87}, number={15}, journal={Applied Physics Letters}, author={Wang, C. M. and Shutthanandan, V. and Thevuthasan, S. and Duscher, G.}, year={2005}, pages={153104} } @article{shao_chisholm_duscher_bonnell_2005, title={Low-temperature resistance anomaly at SrTiO3 grain boundaries: Evidence for an interface-induced phase transition}, volume={95}, number={19}, journal={Physical Review Letters}, author={Shao, R. and Chisholm, M. F. and Duscher, G. and Bonnell, D. A.}, year={2005} } @article{stoddard_duscher_karoui_stevie_rozgonyi_2005, title={Segregation and enhanced diffusion of nitrogen in silicon induced by low energy ion bombardment}, volume={97}, ISSN={["1089-7550"]}, DOI={10.1063/1.1866480}, abstractNote={A sample of nitrogen-doped, single crystal Czochralski silicon was subjected to several different surface preparations. Secondary ion mass spectrometry depth profiling has shown that prolonged glancing-angle bombardment by 3–5kV Ar+ ions significantly increases the nitrogen concentration in the near surface by up to an order of magnitude over the bulk value. Concentrations are observed to be elevated over the bulk value to a depth up to 25μm. Nitrogen-implanted samples and samples with a 1nm surface nitride did not exhibit nitrogen segregation under the same conditions, but a sample with 100nm of surface nitride did exhibit ion bombardment induced drive-in. In nitride-free samples, the source of the nitrogen is indicated to be a nitrogen-rich layer in the first micron of material. The diffusion behavior of nitrogen in silicon is discussed and the Crowdion mechanism for diffusion is suggested as the enabling mechanism for the enhanced low temperature diffusion.}, number={8}, journal={JOURNAL OF APPLIED PHYSICS}, author={Stoddard, N and Duscher, G and Karoui, A and Stevie, F and Rozgonyi, G}, year={2005}, month={Apr} } @article{wang_zhang_shutthanandan_baer_weber_thomas_thevuthasan_duscher_2005, title={Self-assembling of nanocavities in TiO2 dispersed with Au nanoclusters}, volume={72}, number={24}, journal={Physical Review. B, Condensed Matter and Materials Physics}, author={Wang, C. M. and Zhang, Y. and Shutthanandan, V. and Baer, D. R. and Weber, W. J. and Thomas, L. E. and Thevuthasan, S. and Duscher, G.}, year={2005} } @article{wang_baer_thomas_amonette_antony_qiang_duscher_2005, title={Void formation during early stages of passivation: Initial oxidation of iron nanoparticles at room temperature}, volume={98}, number={9}, journal={Journal of Applied Physics}, author={Wang, C. M. and Baer, D. R. and Thomas, L. E. and Amonette, J. E. and Antony, J. and Qiang, Y. and Duscher, G.}, year={2005} } @article{kvit_karoui_duscher_rozgonyi_2004, title={"Umbrella"-like precipitates in nitrogen-doped Czochralski silicon wafers}, volume={84}, ISSN={["1077-3118"]}, DOI={10.1063/1.1669069}, abstractNote={Nitrogen effect on nucleation of oxygen precipitates in Czochralski Si has been investigated by transmission electron microscopy, Z-contrast imaging, and electron energy loss spectrometry (EELS). We have examined unusual “umbrella” shape oxygen precipitates in bulk of ingot in depths of more than 40 μm. Two predominant orientations of “umbrella” have been found along [110] and [−1−10] directions. We have investigated the distribution of nitrogen, oxygen, and interstitial Si by EELS profile taken simultaneously with HR Z-contrast image. The mechanism of nitrogen-enriched oxygen precipitates nucleation has been discussed.}, number={11}, journal={APPLIED PHYSICS LETTERS}, author={Kvit, A and Karoui, A and Duscher, G and Rozgonyi, GA}, year={2004}, month={Mar}, pages={1889–1891} } @article{duscher_chisholm_alber_ruhle_2004, title={Bismuth-induced embrittlement of copper grain boundaries}, volume={3}, ISSN={["1476-4660"]}, DOI={10.1038/nmat1191}, abstractNote={Catastrophic brittle fracture of crystalline materials is one of the best documented but most poorly understood fundamental phenomena in materials science. Embrittlement of copper by bismuth is a classic example of this phenomenon. Because brittle fracture in any structural material can involve human tragedy, a better understanding of the mechanisms behind it is of the highest interest. In this study, we use a combination of two state-of-the-art atomic characterization techniques and ab initio theoretical materials simulations to investigate the geometric and electronic structure of a copper grain boundary with and without bismuth. Only with this unique combination of methods are we able to observe the actual distribution of bismuth in the boundary and detect changes in the electronic structure caused by the bismuth impurity. We find that the copper atoms that surround the segregated bismuth in the grain boundary become embrittled by taking on a more zinc-like electronic structure.}, number={9}, journal={NATURE MATERIALS}, author={Duscher, G and Chisholm, MF and Alber, U and Ruhle, M}, year={2004}, month={Sep}, pages={621–626} } @article{campbell_plitzko_king_foiles_kisielowski_duscher_2004, title={Copper segregation to the Sigma 5 (310)/[001] symmetric tilt grain boundary in aluminum}, volume={12}, ISSN={["0927-7056"]}, DOI={10.1023/B:INTS.0000028647.72322.90}, number={2-3}, journal={INTERFACE SCIENCE}, author={Campbell, GH and Plitzko, JM and King, WE and Foiles, SM and Kisielowski, C and Duscher, GJM}, year={2004}, pages={165–174} } @article{wang_shutthanandan_zhang_thevuthasan_duscher_2004, title={Direct observation of substitutional Au atoms in SrTiO3}, volume={70}, number={17}, journal={Physical Review. B, Condensed Matter and Materials Physics}, author={Wang, C. M. and Shutthanandan, V. and Zhang, Y. and Thevuthasan, S. and Duscher, G}, year={2004} } @article{wang_zhang_shutthanandan_thevuthasan_duscher_2004, title={Microstructure of precipitated au nanoclusters in TiO2}, volume={95}, ISSN={["1089-7550"]}, DOI={10.1063/1.1748859}, abstractNote={Gold nanoclusters dispersed in TiO2(110) single crystal have been formed by 2 MeV Au2+ implantation to an ion fluence of 6.0×1016 cm−2 at 300 and 975 K followed by annealing at 1275 K for 10 h. The morphological features, size, crystallographic orientation of the Au nanoclusters with respect to the TiO2 matrix, and the interface structure between the Au nanoclusters and TiO2 have been investigated using conventional transmission electron microscopy (TEM), high-resolution TEM (HRTEM), electron diffractions, and high angle annular dark-field (HAADF) imaging in an aberration corrected scanning TEM (STEM). STEM-HAADF image directly reveals that Au atoms are in the substitutional Ti atomic columns in the TiO2 lattice prior to nucleation of Au cluster. An Atomic structural model of the interface between Au and TiO2 was established based on HRTEM and image simulations. The precipitated Au clusters show typical (111) twins. Au clusters are faceted along Au{112}, Au{111}, and Au{220} planes. Two types of orientation relationship can be identified, Au〈110〉//TiO2[001] and Au{111}//TiO2(200), and Au〈110〉//TiO2[001] and Au{111}//TiO2(110). These orientation relationships as well as the {111} twining feature in Au clusters are similarly observed for Au clusters grown on stoichiometric TiO2(110) free surface, indicating that the presently established orientation corresponds to the lowest interfacial energy for Au contacted with TiO2. This is essential for understanding the catalytic properties of Au supported on TiO2.}, number={12}, journal={JOURNAL OF APPLIED PHYSICS}, author={Wang, CM and Zhang, Y and Shutthanandan, V and Thevuthasan, S and Duscher, G}, year={2004}, month={Jun}, pages={8185–8193} } @article{windl_liang_lopatin_duscher_2004, title={Modeling and characterization of atomically sharp "perfect" Ge/SiO2 interfaces}, volume={114-15}, number={Dec 15 2004}, journal={Materials Science & Engineering. B, Solid-state Materials for Advanced Technology}, author={Windl, W. and Liang, T. and Lopatin, S. and Duscher, G.}, year={2004}, pages={156–161} } @article{wang_shutthanandan_zhang_thomas_baer_thevuthasan_duscher_2004, title={Precipitation of Au nanoclusters in SrTiO3 by ion implantation}, volume={95}, ISSN={["1089-7550"]}, DOI={10.1063/1.1691187}, abstractNote={Gold nanoclusters dispersed in single-crystal SrTiO3 (STO) (001) have been prepared by ion implantation at both 300 and 975 K followed by annealing at 1275 K for 10 h. High-resolution transmission electron microscopy (TEM), high-angle annular dark-field imaging in an aberration-corrected dedicated scanning TEM, and image simulations were used to study the morphology, size, and crystallographic orientation of the Au nanoclusters with respect to the STO matrix, as well as the interface structure between the Au nanoclusters and STO. Gold ion implantation at 300 K leads to amorphization of the STO surface layer, which is corrugated to form bumps and valleys on the surface. Annealing at 1275 K for 10 h leads to epitaxial recrystallization of the amorphized layer within which Au clusters of several nanometers and a narrow size distribution were formed. Implantation at 975 K and subsequent annealing produces much larger Au clusters ∼50 nm in diameter and a very wide size distribution. The precipitated Au clusters possess an epitaxial orientation with the STO, such that Au[001]//STO[001] and Au(100)//STO(100). The critical cluster size for transition from strain-matched interfaces to dislocation relaxed interfaces has been found to be ∼7 nm. Cavities formed by condensation of vacancies were faceted along {001} and {011} planes in the STO matrix. It is generally inferred that implantation below a critical temperature may lead to a finer Au cluster size.}, number={9}, journal={JOURNAL OF APPLIED PHYSICS}, author={Wang, CM and Shutthanandan, V and Zhang, Y and Thomas, LE and Baer, DR and Thevuthasan, S and Duscher, G}, year={2004}, month={May}, pages={5060–5068} } @article{pennycook_lupini_kadavanich_mcbrid_rosenthal_puetter_yahil_krivanek_dellby_nellist_et al._2022, title={Aberration-corrected scanning transmission electron microscopy: the potential for nano- and interface science}, volume={94}, ISSN={["2195-8556"]}, DOI={10.1515/ijmr-2003-0065}, abstractNote={Abstract The sub-Ångström probe of an aberration-corrected scanning transmission electron microscope will enable imaging and analysis of nanostructures and interfaces with unprecedented resolution and sensitivity. In conjunction with first-principles theory, new insights are anticipated into the atomistic processes of growth and the subtle link between structure and functionality. We present initial results from the aberration-corrected microscopes at Oak Ridge National Laboratory that indicate the kinds of studies that will become feasible in the near future. Examples include (1) the three-dimensional location and identification of individual dopant and impurity atoms in semiconductor interfaces, and their effect on local electronic structure; (2) the accurate reconstruction of surface atomic and electronic structure on nanocrystals, and the effect on optical properties; and (3) the ability to distinguish which configurations of catalyst atoms are active, and why.}, number={4}, journal={INTERNATIONAL JOURNAL OF MATERIALS RESEARCH}, author={Pennycook, S. J. and Lupini, A. R. and Kadavanich, A. and McBrid, J. R. and Rosenthal, S. J. and Puetter, R. C. and Yahil, A. and Krivanek, L. and Dellby, N. and Nellist, P. D. L. and et al.}, year={2022}, month={Feb}, pages={350–357} } @article{pennycook_lupini_kadavanich_mcbride_rosenthal_puetter_yahil_krivanek_dellby_nellist_et al._2003, title={Aberration-corrected scanning transmission electron microscopy: the potential for nano- and interface science}, volume={94}, number={4}, journal={Zeitschrift fur MetallkundeAmerican Journal of Physiology}, author={Pennycook, S. J. and Lupini, A. R. and Kadavanich, A. and Mcbride, J. R. and Rosenthal, S. J. and Puetter, R. C. and Yahil, A. and Krivanek, O. L. and Dellby, N. and Nellist, P. D. L. and et al.}, year={2003}, pages={350–357} } @article{gupta_wang_kvit_duscher_narayan_2003, title={Effect of microstructure on diffusion of copper in TiN films}, volume={93}, ISSN={["1089-7550"]}, DOI={10.1063/1.1566472}, abstractNote={We investigated the effect of the microstructure of TiN films on the diffusion behavior of Cu. Cu/TiN films were synthesized on Si(100) substrate by the pulsed laser deposition (PLD) technique. Three different microstructures of TiN were achieved by growing the films at different substrate temperatures, where higher deposition temperatures (∼650 °C) led to epitaxial growth by the mechanism of domain matching epitaxy and lower temperature depositions resulted in polycrystalline and nanocrystalline TiN films. These structures were characterized using x-ray diffraction and high-resolution transmission electron microscopy. Cu was deposited in situ on the samples with three different microstructures of TiN films on Si(100) by PLD. All three samples were simultaneously annealed at 500 °C for 30 min in high vacuum to study the effect of diffusion characteristics of Cu as a function of microstructure of the TiN films. Secondary ion mass spectroscopy, Z-contrast imaging and electron energy-loss spectroscopy were used to understand the diffusion mechanisms and rationalize results in different microstructures.}, number={9}, journal={JOURNAL OF APPLIED PHYSICS}, author={Gupta, A and Wang, H and Kvit, A and Duscher, G and Narayan, J}, year={2003}, month={May}, pages={5210–5214} } @article{kvit_yankov_duscher_rozgonyi_glasko_2003, title={Formation of nanoscale voids and related metallic impurity gettering in high-energy ion-implanted and annealed epitaxial silicon}, volume={83}, ISSN={["0003-6951"]}, DOI={10.1063/1.1601678}, abstractNote={We have examined nanovoid formation, Fe gettering, and Fe clustering phenomena occurring in epitaxial silicon layers implanted with MeV Si ions. Insights into these phenomena as a function of depth have been gained from detailed analyses by Z-contrast imaging in conjunction with electron energy-loss spectroscopy. Our work has shown at the nanoscale structural and chemical levels that the defects produced by MeV self-ion implantation between the surface and the ion projected range Rp (i.e., in the so-called Rp/2 region) are voids, which provide extremely efficient and aggressive metallic impurity gettering. It has been proposed that the gettering does not occur via chemisorption or silicidation layering on the internal surface of the void walls, as in the well-known case of helium-induced cavities, but rather proceeds in a mode of metal–metal atom binding in the vicinity of the Rp/2 voids.}, number={7}, journal={APPLIED PHYSICS LETTERS}, author={Kvit, A and Yankov, RA and Duscher, G and Rozgonyi, G and Glasko, JM}, year={2003}, month={Aug}, pages={1367–1369} } @article{stoddard_karoui_duscher_kvit_rozgonyi_2003, title={In situ point defect generation and agglomeration during electron-beam irradiation of nitrogen-doped Czochralski silicon}, volume={6}, ISSN={["1944-8775"]}, DOI={10.1149/1.1614471}, abstractNote={Samples of Czochralski silicon were observed after irradiation by a convergent electron beam in a transmission electron microscope. In a nitrogen-doped sample, the 200 keV electrons induced a vacancy-rich region containing point-defect clusters, surrounded by a ring rich in self-interstitials. No comparable effect existed in nitrogen-free reference samples. It is proposed that Frenkel pairs, created by electron collisions, are separated and stabilized by nitrogen or related complexes. Some interstitials become free to diffuse while the nitrogen, vacancies and oxygen agglomerate. This study demonstrates that the initial formation of voids and precipitate nuclei from point defects can be observed at low temperatures. © 2003 The Electrochemical Society. All rights reserved.}, number={11}, journal={ELECTROCHEMICAL AND SOLID STATE LETTERS}, author={Stoddard, N and Karoui, A and Duscher, G and Kvit, A and Rozgonyi, G}, year={2003}, month={Nov}, pages={G134–G136} } @article{rozgonyi_karoui_kvit_duscher_2003, title={Nano-scale analysis of precipitates in nitrogen-doped Czochralski silicon}, volume={66}, ISSN={["1873-5568"]}, DOI={10.1016/S0167-9317(02)00923-1}, abstractNote={Nitrogen-doped Czochralski (CZ) silicon wafers were heat treated with Lo-Hi annealing in argon. Nanoscale defects were then examined by high resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) in the Z-contrast mode, and electron energy loss spectroscopy (EELS) analyses using a field emission JEOL 2010 with a resolution below 2 A. The structures of precipitates, stacking faults and interstitial aggregates were found to depend on their location relative to the wafer surface. Precipitate composition, strain at the interface and interface roughness were obtained and are discussed in connection with the point defects generated during crystal growth and modified during wafer annealing. An excellent correlation was found between Z-contrast line scans across the precipitates and the N to O concentration ratio determined with EELS. In the precipitate central region that ratio is between 1 and 6%, whereas at precipitate boundaries it reaches 17%.}, number={1-4}, journal={MICROELECTRONIC ENGINEERING}, author={Rozgonyi, GA and Karoui, A and Kvit, A and Duscher, G}, year={2003}, month={Apr}, pages={305–313} } @article{haverkamp_mayo_bourham_narayan_jin_duscher_2003, title={Plasma plume characteristics and properties of pulsed laser deposited diamond-like carbon films}, volume={93}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.1555695}, DOI={10.1063/1.1555695}, abstractNote={Pulsed laser deposition is a unique technique for the deposition of hydrogen-free diamond-like carbon films. During deposition, amorphous carbon is evaporated from a solid target by a high-energy KrF laser, ionized, and ejected as a plasma plume. The plume expands outwards and deposits the target material on a substrate. The plasma properties of the plume determine the quality of the thin films deposited on the substrate. These plume properties include ion density, ion flow speed, electron temperature, and plume peaking parameter. In this research, a triple Langmuir probe is used to determine various plasma properties of the plume created from the pulsed laser ablation of amorphous graphite as a function of laser energy density and laser spot size on the target. A thin diamond-like carbon film is deposited and analyzed with electron energy-loss spectroscopy to determine the sp3/sp2 fraction. A special preparation technique was used to prepare the thin film for analysis to prevent the damage that may be caused by conventional ion milling techniques.}, number={6}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Haverkamp, J. and Mayo, R. M. and Bourham, M. A. and Narayan, J. and Jin, C. and Duscher, G.}, year={2003}, month={Mar}, pages={3627–3634} } @article{kumar_pennycook_lupini_duscher_tiwari_narayan_2002, title={Synthesis and atomic-level characterization of Ni nanoparticles in Al2O3 matrix}, volume={81}, ISSN={["0003-6951"]}, DOI={10.1063/1.1525052}, abstractNote={Single domain magnetic nickel nanocrystals were embedded in alumina matrix using a pulsed-laser deposition technique. Structural characterization carried out at the atomic level using scanning transmission electron microscopy with atomic number contrast (STEM-Z) in conjunction with electron energy loss spectroscopy have revealed that the Ni particles are well separated and have interfaces with the host matrix that are atomically sharp and free of any oxide layer. An excellent correlation was found between particle sizes determined theoretically from magnetization versus field data and experimentally using STEM-Z which indicates the absence of any magnetically dead layers on the Ni nanoparticles within an experimental error of 0.1 monolayer.}, number={22}, journal={APPLIED PHYSICS LETTERS}, author={Kumar, D and Pennycook, SJ and Lupini, A and Duscher, G and Tiwari, A and Narayan, J}, year={2002}, month={Nov}, pages={4204–4206} } @article{lopatin_pennycook_narayan_duscher_2002, title={Z-contrast imaging of dislocation cores at the GaAs/Si interface}, volume={81}, ISSN={["0003-6951"]}, DOI={10.1063/1.1511808}, abstractNote={The interface between silicon and epitaxial GaAs thin film grown by metalorganic chemical vapor deposition was studied using atomic-resolution Z-contrast imaging. Z-contrast imaging provides chemical composition information and allows direct interpretation of micrographs without simulation. Three different types of dislocations were identified. As expected, a dangling bond was found in the atomic structure of the 60° dislocation. One of the observed 90° dislocations had the reconstructed atomic core structure (with no dangling bonds). The core structure of the other 90° dislocation exhibited a dangling bond.}, number={15}, journal={APPLIED PHYSICS LETTERS}, author={Lopatin, S and Pennycook, SJ and Narayan, J and Duscher, G}, year={2002}, month={Oct}, pages={2728–2730} } @article{smith_french_duscher_bonnell_2001, title={Consequence of nanometer-scale property variations to macroscopic properties of CrOCN thin films}, volume={84}, ISSN={["0002-7820"]}, DOI={10.1111/j.1151-2916.2001.tb01108.x}, abstractNote={Macroscopic properties of CrOCN thin films are related directly to composition and property variations on multiple length scales. Compositions resolved on a nanometer scale were measured in‐depth in 120–150 nm thick CrOCN films by sputtered neutral mass spectroscopy. A statistical analysis of composition identifies the particular coordinations of the various anions with Cr that form preferentially under relevant processing conditions. Near‐edge structure in electron energy loss from transmission electron microscopy and the Cr core level shift in X‐ray photoemission spectroscopy further support this conclusion. A wide range of compositions are described in terms of mixtures of binary and ternary compounds, and optical absorption is found to be correlated with the presence of Cr4+ within this description. It appears that the presence of the unfilled t2g state is responsible for optical absorption in the range of 0.5–6 eV and that a critical concentration of Cr4+ in certain species within the system is required for the transition to occur. These results conflict with the suggestion that a percolated network of metallic clusters is responsible for the change in properties.}, number={12}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Smith, J and French, RH and Duscher, G and Bonnell, D}, year={2001}, month={Dec}, pages={2873–2881} } @article{wagner_marien_duscher_2001, title={Cu, Nb and V on (110) TiO2 (rutile): epitaxy and chemical reactions}, volume={398}, ISSN={["1879-2731"]}, DOI={10.1016/S0040-6090(01)01351-7}, abstractNote={Thin metal films on oxide substrates are used in a variety of technological applications including microelectronic devices, catalysts and sensors. Ideally, the films should have low defect densities. This prerequisite can often be fulfilled by growing epitaxial films. Recently, epitaxial films have received a great deal of attention for fundamental studies of the structure and bonding of heterophase interfaces. In this paper, fundamental investigations of the interface formation for MBE deposited metals (Cu, Nb, V) on TiO2 single crystals (rutile) will be presented. The structure and chemical composition of the metal/oxide interfaces were determined by a variety of surface science and transmission electron microscopy methods. We conclude on general trends, which allow the prediction of the growth behavior of metals on oxides as a function of processing and material parameters.}, journal={THIN SOLID FILMS}, author={Wagner, T and Marien, J and Duscher, G}, year={2001}, month={Nov}, pages={419–426} }