@article{tawancy_aboelfotoh_hassan_alhems_2021, title={Synthesis of superlattice heterostructure of germanium quantum dots in silicon spacer layers and its application in photovoltaic solar cells}, volume={155}, ISSN={["1096-3677"]}, DOI={10.1016/j.spmi.2021.106924}, abstractNote={Superlattice heterostructure of dislocation-free Ge quantum dots buried in Si spacer layers has been synthesized using ultra high vacuum-chemical vapor deposition technique. The heterostructure has been used as active layer in Si solar cells based upon vertical p-i-n junction configuration. Experiment shows that such solar cells exhibit strong repose to infrared radiation in contrast with the negligible response of solar cells with active layers of pure Si having the same thickness. A solar cell with 300 nm thick superlattice is shown to have thermodynamic efficiency of about 11.2%. This is correlated with the rather high quality of the heterostructure used in the present study as judged from photoluminescence spectroscopy and electron microscopy as well as strain and dark current measurements. It is concluded that such type of heterostructure may provide a pathway to develop efficient and cost effective solar cells.}, journal={SUPERLATTICES AND MICROSTRUCTURES}, author={Tawancy, H. M. and Aboelfotoh, M. O. and Hassan, Mohamed A. and Alhems, L. M.}, year={2021}, month={Jul} }
 @article{tawancy_aboelfotoh_2018, title={Analysis of the Ordered Crystal Structure of Cu3Ge Intermetallic}, volume={7}, ISSN={["2192-9270"]}, DOI={10.1007/s13632-018-0491-9}, number={6}, journal={METALLOGRAPHY MICROSTRUCTURE AND ANALYSIS}, author={Tawancy, H. M. and Aboelfotoh, M. O.}, year={2018}, month={Dec}, pages={769–775} }
 @article{tawancy_alhems_aboelfotoh_2017, title={Performance of bond coats modified by platinum group metals for applications in thermal barrier coatings}, volume={26}, number={7}, journal={Journal of Materials Engineering and Performance}, author={Tawancy, H. M. and Alhems, L. M. and Aboelfotoh, M. O.}, year={2017}, pages={3191–3203} }
 @article{tawancy_aboelfotoh_2014, title={Mechanical properties of ground state structures in substitutional ordered alloys: High strength, high ductility and high thermal stability}, volume={603}, journal={Materials Science & Engineering. A, Structural Materials: Properties, Microstructure and Processing}, author={Tawancy, H. M. and Aboelfotoh, M. O.}, year={2014}, pages={121–128} }
 @article{lampert_lappi_papanikolas_reynolds_aboelfotoh_2013, title={Morphology and chain aggregation dependence of optical gain in thermally annealed films of the conjugated polymer poly[2-methoxy-5-(2 '-ethylhexyloxy)-p-phenylene vinylene]}, volume={113}, number={23}, journal={Journal of Applied Physics}, author={Lampert, Z. E. and Lappi, S. E. and Papanikolas, J. M. and Reynolds, C. L. and Aboelfotoh, M. O.}, year={2013} }
 @misc{bouchier_aboelfotoh_2012, title={Comments on the article: "Enhancing the photovoltaic effect in the infrared region by germanium quantum dots inserted in the intrinsic region of a silicon p-i-n diode with nanostructure" by H. M. Tawancy (Journal of Materials Science DOI: 10.1007/s10853-0}, volume={47}, number={1}, journal={Journal of Materials Science}, author={Bouchier, D. and Aboelfotoh, O.}, year={2012}, pages={100–103} }
 @article{lampert_reynolds_papanikolas_aboelfotoh_2012, title={Controlling Morphology and Chain Aggregation in Semiconducting Conjugated Polymers: The Role of Solvent on Optical Gain in MEH-PPV}, volume={116}, ISSN={["1520-5207"]}, DOI={10.1021/jp304199u}, abstractNote={We report the results of a detailed investigation that addresses the influence of polymer morphology and chain aggregation, as controlled by the chemical nature of the solvent, on the optical gain properties of the conjugated polymer poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV). Using the variable stripe length technique in the picosecond regime, we have extensively studied the optical gain performance of asymmetric planar waveguides formed with thin MEH-PPV films spin-cast from concentrated chlorobenzene (CB) and tetrahydrofuran (THF) solutions onto thermally oxidized silicon substrates. CB and THF solvents were chosen based on their known ability to promote and effectively limit aggregate formation, respectively. Very large net gain coefficients are demonstrated, reaching values of 330 and 365 cm(-1), respectively, when optically pumping the waveguides with a maximum energy density of 85 μJ/cm(2). Our results clearly demonstrate that polymer morphology, and hence, the chain conformation dependence of the degree of aggregation in the films as controlled by the solvent, has minimal impact on the net gain. Moreover, the waveguides exhibit low loss coefficients of 10-20 cm(-1) at the ASE wavelength. These results question the importance of polymer morphology and aggregate formation in polymer-based optical devices operating at high excitation densities in the stimulated emission regime as would be characteristic of lasers and optical amplifiers.}, number={42}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Lampert, Zach E. and Reynolds, C. Lewis, Jr. and Papanikolas, John M. and Aboelfotoh, M. Osama}, year={2012}, month={Oct}, pages={12835–12841} }
 @article{tawancy_aboelfotoh_2010, title={Yttrium-doped nanocrystalline Ni4Mo: Ultrahigh strength and high ductility combined with useful intermetallic properties}, volume={45}, number={13}, journal={Journal of Materials Science}, author={Tawancy, H. M. and Aboelfotoh, M. O.}, year={2010}, pages={3413–3418} }
 @article{tawancy_aboelfotoh_2009, title={Application of long-range ordering in the synthesis of a nanoscale Ni-2 (Cr,Mo) superlattice with high strength and high ductility}, volume={500}, number={1-2}, journal={Materials Science & Engineering. A, Structural Materials: Properties, Microstructure and Processing}, author={Tawancy, H. M. and Aboelfotoh, M. O.}, year={2009}, pages={188–195} }
 @article{tawancy_ui-hamid_abbas_aboelfotoh_2008, title={Effect of platinum on the oxide-to-metal adhesion in thermal barrier coating systems}, volume={43}, ISSN={["0022-2461"]}, DOI={10.1007/s10853-007-2130-8}, number={9}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Tawancy, H. M. and Ui-Hamid, A. and Abbas, N. M. and Aboelfotoh, M. O.}, year={2008}, month={May}, pages={2978–2989} }
 @article{tawancy_aboelfotoh_2008, title={High strength and high ductility in a nanoscale superlattice of Ni-2(Cr,Mo) deformable by twinning}, volume={59}, ISSN={["1359-6462"]}, DOI={10.1016/j.scriptamat.2008.06.026}, abstractNote={It is demonstrated that long-range ordering can be utilized to synthesize a nanoscale superlattice of Ni2(Cr,Mo) in a Ni–18.6 at.% Mo–15.1 at.% Cr. The superlattice is distinguished by high strength and high ductility. This behavior has been correlated with the crystallography of the disorder–order transformation, which favors deformation by twinning on the {1 1 1} planes of the parent face-centered cubic structure.}, number={8}, journal={SCRIPTA MATERIALIA}, author={Tawancy, H. M. and Aboelfotoh, M. O.}, year={2008}, month={Oct}, pages={846–849} }
 @article{darling_guduru_reynolds_bhosle_chan_scattergood_koch_narayan_aboelfotoh_2008, title={Thermal stability, mechanical and electrical properties of nanocrystalline Cu3Ge}, volume={16}, ISSN={0966-9795}, url={http://dx.doi.org/10.1016/j.intermet.2007.11.005}, DOI={10.1016/j.intermet.2007.11.005}, abstractNote={The intermetallic ɛ1 compound Cu3Ge was produced through a mechanical alloying procedure that enables the formation of a nanograined microstructure. There is a dependence of grain size (20–11 nm) on milling conditions. The microstructure remained very stable even at temperatures up to 500 °C for 5 h which is a minimum of 76% of the melting temperature. The materials produced by these methods were in the form of powders with particle size ranging from 200 nm to 10 μm. The morphology of the particles varied with the largest being rough and irregular and the smallest being spherical. Preliminary resistivity measurements showed low resistivity, 8.8 μΩ cm, which is comparable to that previously reported for thin films with grain sizes thousands of times larger. Nanoindentation was also performed, yielding an elastic modulus of ∼110 GPa.}, number={3}, journal={Intermetallics}, publisher={Elsevier BV}, author={Darling, Kris A. and Guduru, R.K. and Reynolds, C. Lewis, Jr and Bhosle, Vikram M. and Chan, Ryan N. and Scattergood, Ronald O. and Koch, Carl C. and Narayan, J. and Aboelfotoh, M.O.}, year={2008}, month={Mar}, pages={378–383} }
 @article{aboelfotoh_frojdh_petersson_2003, title={Schottky-barrier behavior of metals on n- and p-type 6H-SiC}, volume={67}, number={7}, journal={Physical Review. B, Condensed Matter and Materials Physics}, author={Aboelfotoh, M. O. and Frojdh, C. and Petersson, C. S.}, year={2003}, pages={075312–1} }
 @article{hattab_aboelfotoh_tremblay_meyer_kolodzey_osten_dubois_2002, title={Diffusion and electrical activity of copper in Si1-x-yGexCy alloys}, volume={60}, DOI={10.1016/S0167-9317(01)00605-0}, abstractNote={We investigate copper diffusion in Si-rich Si1−x−yGexCy (x<20%) and Ge-rich (x=93%) Si1−xGex layers. The profiles of the different constituents (Si, Ge, Cu, C, B) were determined using secondary ion mass spectroscopy (SIMS). Carrier profiles were studied by electrical characterizations of Schottky diodes. The structures were prepared by copper deposition on SiGeC alloys at room temperature. The increase of the Ge-content from 0% to 93% results in a decrease of the Cu diffusion depth determined by SIMS. C-incorporation also leads to a reduction of Cu-diffusion. The effect of boron seems to be more important, and Cu-diffusion is well retarded in p-type samples. The electrical activity of Cu in IV–IV alloys depends on the Ge-content. For Si-rich p-type SiGe alloy, we observed a passivation of the boron acceptors attributed to the formation of Cu–B pairs, which also explains the reduction of Cu diffusion. For p-type Ge-rich samples, the acceptor concentration can reach very high values (larger than the boron concentration), and becomes temperature dependent. These results show that boron passivation is no longer the most important effect of Cu diffusion. We suggest that the presence of Cu in Ge-rich alloys produces an acceptor-like trap.}, number={1-2}, journal={Microelectronic Engineering}, author={Hattab, A. and Aboelfotoh, M. O. and Tremblay, G. and Meyer, F. and Kolodzey, J. and Osten, H. J. and Dubois, C.}, year={2002}, pages={283–288} }
 @article{barthula_aboelfotoh_meyer_2001, title={Copper passivation of boron in Si1-xGex alloys and boron reactivation kinetics}, volume={55}, DOI={10.1016/S0167-9317(00)00463-9}, abstractNote={Abstract Copper passivation of boron in SiGe layers has been investigated by the use of Schottky barrier structures prepared by the deposition of copper on boron-doped SiGe alloys at room temperature. The boron passivation occurs at room temperature after Cu deposition and diffusion in the alloy. The Cu diffusivity is enhanced by dislocations and retarded by increasing the Ge content and (or) the compressive strain. The mechanisms for passivation seem similar to those evidenced for pure silicon: the fast-diffusing interstitial Cu + passivates the boron acceptors by forming neutral B–Cu complexes. The reactivation of boron is partially obtained after annealing at 200°C while the Cu 3 Si 1− x Ge x phase is formed. The reaction kinetics are first order with an activation energy of 0.76 eV.}, number={1-4}, journal={Microelectronic Engineering}, author={Barthula, M. and Aboelfotoh, M. O. and Meyer, F.}, year={2001}, pages={323–328} }
 @article{teng_aboelfotoh_davis_muth_kolbas_2001, title={Photoluminescence and electrical characteristics of the two-dimensional electron gas in Si delta-doped GaN layers}, volume={78}, ISSN={["1077-3118"]}, DOI={10.1063/1.1353836}, abstractNote={We have studied the electrical and photoluminescence (PL) properties of a Si delta-doped GaN layer grown by metalorganic chemical vapor deposition. The Hall mobility and electron sheet concentration are 726 cm2/V s and 1.9×1012 cm−2, respectively, at 2 K. A PL peak located at 78 meV below the band gap of GaN is observed at 77 K. This PL peak is attributed to the radiative recombination between electrons in the two-dimensional quantum states and photoexcited holes in GaN, which is consistent with simulation results using a one-dimensional Poisson and Schrödinger equation solver. The peak disappears at temperatures higher than 77 K and is not observed in uniformly doped GaN layers.}, number={12}, journal={APPLIED PHYSICS LETTERS}, author={Teng, CW and Aboelfotoh, MO and Davis, RF and Muth, JF and Kolbas, RM}, year={2001}, month={Mar}, pages={1688–1690} }
 @article{aboelfotoh_borek_narayan_2000, title={Microstructure and electrical resistivity of Cu and Cu3Ge thin films on Si1-xGex alloy layers}, volume={87}, ISSN={["0021-8979"]}, DOI={10.1063/1.371868}, abstractNote={We have studied the reaction between Cu and ε1-Cu3Ge thin films and Si1−xGex (x=0.5) alloy layers epitaxially grown on Si(100) in the temperature range of 250–400 °C. In this temperature range, Cu reacts with the alloy to form a Cu3Si1−xGex ternary phase with an ordered body-centered-cubic crystal structure, and no Ge segregation occurs during the reaction. Unlike ε1-Cu3Ge, the Cu3Si1−xGex films exhibit a high-room-temperature resistivity of ∼150 μΩ cm. However, the Cu3Si1−xGex phase is not observed when Ge is added to Cu to form ε1-Cu3Ge. In contrast to the results reported for films of ε1-Cu3Ge formed on Si(100) substrates, the outdiffusion of Si into the ε1-Cu3Ge films is found to be suppressed when the films are formed on Si0.5Ge0.5 layers at temperatures up to 500 °C, and their resistivity remains low (typically less than 10 μΩ cm at room temperature), indicating the increased stability of ε1-Cu3Ge on Si1−xGex alloys. Furthermore, the ε1-Cu3Ge films form a sharp interface with the Si0.5Ge0.5 layers. These results indicate that ε1-Cu3Ge is an attractive candidate for contacts to SiGe-based devices.}, number={1}, journal={JOURNAL OF APPLIED PHYSICS}, author={Aboelfotoh, MO and Borek, MA and Narayan, J}, year={2000}, month={Jan}, pages={365–368} }
 @article{aboelfotoh_doyle_1999, title={Defect energy levels in electron-irradiated and deuterium- implanted 6H silicon carbide}, volume={59}, number={16}, journal={Physical Review. B, Condensed Matter and Materials Physics}, author={Aboelfotoh, M. O. and Doyle, J. P.}, year={1999}, pages={10823–10829} }
 @article{aboelfotoh_borek_narayan_1999, title={Interaction of Cu and Cu3Ge thin films with Si1-xGex alloys}, volume={75}, ISSN={["0003-6951"]}, DOI={10.1063/1.124804}, abstractNote={The interaction of Cu and Cu3Ge thin films with Si1−xGex (x=0.5) alloy layers epitaxially grown on Si(100) has been studied in the temperature range of 250–400 °C. In this temperature range, Cu reacts with the alloy to form a Cu3(Si1−xGex) ternary phase with an ordered body-centered-cubic crystal structure. The Cu3(Si1−xGex) phase exhibits high-room-temperature (∼150 μΩ cm) and nonmetallic resistivity. However, this ternary phase is not observed and the diffusion of Cu into the alloy is suppressed when Cu is replaced by low resistivity (typically less than 10 μΩ cm at room temperature) ε1-Cu3Ge phase. In contrast to the results reported for films of ε1-Cu3Ge formed on Si(100), the outdiffusion of Si into the ε1-Cu3Ge films is found to be suppressed when the films are formed on Si0.5Ge0.5 layers, indicating the increased stability of ε1-Cu3Ge on Si1−xGex alloys compared to pure silicon.}, number={12}, journal={APPLIED PHYSICS LETTERS}, author={Aboelfotoh, MO and Borek, MA and Narayan, J}, year={1999}, month={Sep}, pages={1739–1741} }
 @article{aboelfotoh_borek_narayan_1999, title={Ohmic contact to p-type GaAs using Cu3Ge}, volume={75}, ISSN={["1077-3118"]}, DOI={10.1063/1.125505}, abstractNote={We have investigated ε1−Cu3Ge as an ohmic contact to p-type GaAs, and found that the ε1−Cu3Ge contact has a specific contact resistivity of 5×10−6 Ω cm2 on p-type GaAs with doping concentrations of ∼7×1018 cm−3. The ε1−Cu3Ge contact exhibits a planar and structurally abrupt interface with the GaAs, and no reaction between the contact metal and the GaAs is required for contact formation. The contact is electrically stable during annealing at temperatures up to 400 °C. It is suggested that Ge is incorporated into the GaAs as a p-type impurity resulting in a low contact resistivity. Furthermore, the addition of Ge to Cu to form ε1−Cu3Ge is found to impede the diffusion of Cu into the p-type GaAs. Along with the results reported for n-type GaAs, the present results indicate that ε1−Cu3Ge is an attractive candidate for ohmic contact formation on both n- and p-type GaAs.}, number={25}, journal={APPLIED PHYSICS LETTERS}, author={Aboelfotoh, MO and Borek, MA and Narayan, J}, year={1999}, month={Dec}, pages={3953–3955} }
 @article{aboelfotoh_oktyabrsky_narayan_woodall_1997, title={Electrical and microstructural characteristics of Ge/Cu ohmic contacts to n-type GaAs}, volume={12}, ISSN={["2044-5326"]}, DOI={10.1557/JMR.1997.0308}, abstractNote={It is shown that Cu–Ge alloys prepared by depositing sequentially Cu and Ge layers onto GaAs substrates at room temperature followed by annealing at 400 °C form a low-resistance ohmic contact to n-type GaAs over a wide range of Ge concentration that extends from 15 to 40 at. %. The contacts exhibit a specific contact resistivity of 7 × 10−7 Ω cm2 on n-type GaAs with doping concentrations of 1 × 1017 cm−3. The contact resistivity is unaffected by varying the Ge concentration in the range studied and is not influenced by the deposition sequence of the Cu and Ge layers. Cross-sectional high-resolution transmission electron microscopy results show that the addition of Ge to Cu in this concentration range causes Cu to react only with Ge forming the ξ and ε1–Cu3Ge phases which correlate with the low contact resistivity. The ξ and ε1–Cu3Ge phases have a planar and structurally abrupt interface with the GaAs substrate without any interfacial transition layer. It is suggested that Ge is incorporated into the GaAs as an n-type impurity creating a highly doped n+-GaAs surface layer which is responsible for the ohmic behavior. n-channel GaAs metal-semiconductor field-effect transistors using ohmic contacts formed with the ξ and ε1–Cu3Ge phases demonstrate a higher transconductance compared to devices with AuGeNi contacts.}, number={9}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Aboelfotoh, MO and Oktyabrsky, S and Narayan, J and Woodall, JM}, year={1997}, month={Sep}, pages={2325–2331} }