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Full-Text Articles in Physics
Effect Of Fabrication Parameters On The Ferroelectricity Of Hafnium Zirconium Oxide Films: A Statistical Study, Guillermo A. Salcedo, Ahmad E. Islam, Elizabeth Reichley, Michael Dietz, Christine M. Schubert Kabban, Kevin D. Leedy, Tyson C. Back, Weison Wang, Andrew Green, Timothy S. Wolfe, James M. Sattler
Effect Of Fabrication Parameters On The Ferroelectricity Of Hafnium Zirconium Oxide Films: A Statistical Study, Guillermo A. Salcedo, Ahmad E. Islam, Elizabeth Reichley, Michael Dietz, Christine M. Schubert Kabban, Kevin D. Leedy, Tyson C. Back, Weison Wang, Andrew Green, Timothy S. Wolfe, James M. Sattler
Faculty Publications
Ferroelectricity in hafnium zirconium oxide (Hf1−xZrxO2) and the factors that impact it have been a popular research topic since its discovery in 2011. Although the general trends are known, the interactions between fabrication parameters and their effect on the ferroelectricity of Hf1−xZrxO2 require further investigation. In this paper, we present a statistical study and a model that relates Zr concentration (x), film thickness (tf), and annealing temperature (Ta) with the remanent polarization (Pr) in tungsten (W)-capped Hf1−xZrxO2. …
Electron Traps In Ag-Doped Li2B4O7 Crystals: The Role Of Ag Interstitial Ions, Timothy D. Gustafson, Brant E. Kananen, Nancy C. Giles, Brian C. Holloway, Volodymyr T. Adamiv, Ihor M. Teslyuk, Yaroslav V. Burak, Larry E. Halliburton
Electron Traps In Ag-Doped Li2B4O7 Crystals: The Role Of Ag Interstitial Ions, Timothy D. Gustafson, Brant E. Kananen, Nancy C. Giles, Brian C. Holloway, Volodymyr T. Adamiv, Ihor M. Teslyuk, Yaroslav V. Burak, Larry E. Halliburton
Faculty Publications
Electron paramagnetic resonance (EPR) is used to establish models for electron traps in Ag-doped lithium tetraborate (Li2B4O7) crystals. When exposed at room temperature to ionizing radiation, electrons are trapped at interstitial Ag+ ions and holes are trapped at Ag+ ions on Li+ sites. The trapped electrons occupy a 5s1 orbital on the interstitial Ag ions (some of the unpaired spin density is also on neighboring ions). Three EPR spectra are assigned to electrons trapped at interstitial Ag ions. Their g values are near 1.99 and they have resolved hyperfine structure …
Radiation-Induced Electron And Hole Traps In Ge1-XSnX (X = 0-0.094), Michael R. Hogsed, Kevin Choe, Norman Miguel, Buguo Wang, John Kouvetakis
Radiation-Induced Electron And Hole Traps In Ge1-XSnX (X = 0-0.094), Michael R. Hogsed, Kevin Choe, Norman Miguel, Buguo Wang, John Kouvetakis
Faculty Publications
The band structure of germanium changes significantly when alloyed with a few percent concentrations of tin, and while much work has been done to characterize and exploit these changes, the corresponding deep-level defect characteristics are largely unknown. In this paper, we investigate the dominant deep-level defects created by 2 MeV proton irradiation in Ge1 -xSnx (x = 0.0, 0.020, 0.053, 0.069, and 0.094) diodes and determine how the ionization energies of these defects change with tin concentrations. Deep-level transient spectroscopy measurements approximate the ionization energies associated with electron transitions to/from the valence band (hole traps) and conduction band (electron traps) …
Cathodoluminescence Studies Of Defects In Coated Boron Nitride, Kévin Guerch, Justin Dekany, Jr Dennison, Thierry Paulmier, Sophie Guillemet-Fritsch, Pascal Lenormand
Cathodoluminescence Studies Of Defects In Coated Boron Nitride, Kévin Guerch, Justin Dekany, Jr Dennison, Thierry Paulmier, Sophie Guillemet-Fritsch, Pascal Lenormand
Journal Articles
Optical emission properties of Boron Nitride (BN) substrates, BN with alumina (Al2O3) coating, and thermally-annealed alumina-coated boron nitride (an-BN/Al2O3) were investigated under electron irradiation using cathodoluminescence (CL) measurements. Tests were performed temperatures ranging from ~100 K to ~300 K, with monoenergetic beams from 5 keV to 30 keV, and electron flux densities from 1 nA.cm-2 to 500 nA.cm-2. These experiments were conducted to identify the effects of coating and thermal annealing on the nature and occupation of defect states in different samples with BN substrates. Previous studies have shown that these treatments can limit the charging of BN substrates. Consequently, …
Electrical Properties Of Annealed And Coated Boron Nitride Under Electron Beam Irradiation, Kevin Guerch, Theirry Paulmier, Jr Dennison, Justin Dekany, Pascal Lenormand, Sophie Guillemet-Fritsch
Electrical Properties Of Annealed And Coated Boron Nitride Under Electron Beam Irradiation, Kevin Guerch, Theirry Paulmier, Jr Dennison, Justin Dekany, Pascal Lenormand, Sophie Guillemet-Fritsch
Journal Articles
The charging and relaxation kinetics of pyrolytic boron nitride (BN) substrates, BN with an aluminium oxide (BN/Al2O3) coating, and thermally-annealed alumina-coated boron nitride (an-BN/Al2O3) were investigated under low power electron irradiation (5 < E0 < 20 keV, Ji = 10 nA.cm-2 at room temperature) in the CEDRE facility at ONERA (Toulouse, France). Surface potentials of each ceramics configuration were measured over time using the Kelvin probe method. The influence of coating and annealing treatments to limit charging is discussed in this paper. A thorough study of a an–BN/Al2O3 sample was carried out …
Low Temperature Ordering And High (001) Orientation Of [Fe/Pt/Cu]18 Multilayer Films, Yongsheng Yu, Xingzhong Li, T A. George, W D. Fei, Haibo Li, David J. Sellmyer
Low Temperature Ordering And High (001) Orientation Of [Fe/Pt/Cu]18 Multilayer Films, Yongsheng Yu, Xingzhong Li, T A. George, W D. Fei, Haibo Li, David J. Sellmyer
David Sellmyer Publications
[Fe/Pt/Cu]18 multilayer films with different Cu thicknesses were prepared on thermally oxidized Si (111) substrates at room temperature using dc- and rf-magnetron sputtering. The magnetic proper-ties and microstructure of [Fe/Pt/Cu]18 multilayer films annealed at various temperatures have been investigated. Compared with pure [Fe/Pt]18 multilayer films low-temperature ordering and (001) ori-entation in the annealed films with Cu volume concentration below 20% can be obtained. During annealing process Cu atoms diffused into FePt lattice which enhanced the diffusion of Fe and Pt atoms and the grain growth of the films. The perpendicular anisotropy and hard magnetic properties of the …
Carrier Capture Dynamics Of Single Ingaas/Gaas Quantum-Dot Layers, Kripa N. Chauhaun, D. Mark Riffe, Addison E. Everett, D. J. Kim, H Yang, F. K. Shen
Carrier Capture Dynamics Of Single Ingaas/Gaas Quantum-Dot Layers, Kripa N. Chauhaun, D. Mark Riffe, Addison E. Everett, D. J. Kim, H Yang, F. K. Shen
All Physics Faculty Publications
Using 800nm, 25-fs pulses from a mode locked Ti:Al2O3 laser, we have measured the ultrafast optical reflectivity of MBE-grown, single-layer In0.4Ga0.6As/GaAs quantum-dot (QD) samples. The QDs are formed via two-stage Stranski-Krastanov growth: following initial InGaAs deposition at a relatively low temperature, self assembly of the QDs occurs during a subsequent higher temperature anneal. The capture times for free carriers excited in the surrounding GaAs (barrier layer) are as short as 140fs, indicating capture efficiencies for the InGaAs quantum layer approaching 1. The capture rates are positively correlated with initial InGaAs thickness and annealing temperature. With increasing excited carrier density, the …
Characterization Of A Thermal Reservoir For Consistent And Accurate Annealing Of High Sensitivity Thermoluminescence Dosimeters In Brachytherapy Dosimetry, William Patrick Donahue
Characterization Of A Thermal Reservoir For Consistent And Accurate Annealing Of High Sensitivity Thermoluminescence Dosimeters In Brachytherapy Dosimetry, William Patrick Donahue
Honors Scholar Theses
Unlike regular TLD, an accurate and consistent annealing of the high-sensitivity TLD at 240 ˚C for 15 minutes is challenging using conventional annealing ovens because the temperature in the oven chamber varies drastically over the 15-minute period after the opening (to put the TLD tray in) and closing of oven door. The temperature in the oven drops dramatically after the door is opened and ramps up gradually after the door is closed, often accompanied with significant temperature overshoot. Because an overshoot by more than 5 ˚C can significantly reduce the sensitivity of the TLD and the ramp-up profile varies with …
Stable Highly Conductive Zno Via Reduction Of Zn Vacancies, David C. Look, Timothy C. Droubay, Scott A. Chambers
Stable Highly Conductive Zno Via Reduction Of Zn Vacancies, David C. Look, Timothy C. Droubay, Scott A. Chambers
Physics Faculty Publications
Growth of Ga-doped ZnO by pulsed laser deposition at 200 °C in an ambient of Ar and H2produces a resistivity of 1.5 × 10−4 Ω-cm, stable to 500 °C. The resistivity can be further reduced to 1.2 × 10−4 Ω-cm by annealing on Zn foil, which reduces the compensating Zn-vacancy acceptor concentration NA to 5 × 1019 cm−3, only 3% of the Ga-donor concentration ND of 1.6 × 1021 cm−3, with ND and NA determined from a degenerate mobility theory. The plasmon-resonance wavelength is only 1060 …
Highly Conductive Zno Grown By Pulsed Laser Deposition In Pure Ar, Robin C. Scott, Kevin D. Leedy, Burhan Bayraktaroglu, David C. Look, Yong-Hang Zhang
Highly Conductive Zno Grown By Pulsed Laser Deposition In Pure Ar, Robin C. Scott, Kevin D. Leedy, Burhan Bayraktaroglu, David C. Look, Yong-Hang Zhang
Physics Faculty Publications
Ga-doped ZnO was deposited by pulsed laser deposition at 200 °C on SiO2/Si, Al2O3, or quartz in 10 mTorr of pure Ar. The as-grown, bulk resistivity at 300 K is 1.8×10−4 Ω cm, three-times lower than that of films deposited at 200 °C in 10 mTorr of O2 followed by an anneal at 400 °C in forming gas. Furthermore, depth uniformity of the electrical properties is much improved. Mobility analysis shows that this excellent resistivity is mostly due to an increase in donor concentration, rather than a decrease in acceptor concentration. Optical …
Mobility Analysis Of Highly Conducting Thin Films: Application To Zno, David C. Look, K. D. Leedy, D. H. Tomich, B. Bayraktaroglu
Mobility Analysis Of Highly Conducting Thin Films: Application To Zno, David C. Look, K. D. Leedy, D. H. Tomich, B. Bayraktaroglu
Physics Faculty Publications
Hall-effect measurements have been performed on a series of highly conductive thin films of Ga-doped ZnO grown by pulsed laser deposition and annealed in a forming-gas atmosphere (5% H2 in Ar). The mobility as a function of thickness d is analyzed by a simple formula involving only ionized-impurity and boundary scattering and having a single fitting parameter, the acceptor/donor concentration ratio K = NA/ND. For samples with d = 3–100 nm, Kavg = 0.41, giving ND = 4.7×1020 and NA = 1.9×1020 cm−3. Thicker samples require a …
Chemical Structure Of Vanadium-Based Contact Formation On N-Ain, S. Pookpanratana, R. France, M. Blum, Sean R. Mulcahy, A. Bell, M. Bär, L. Weinhardt, Y. Zhang, T. Hofmann, O. Fuchs, W. Yang, J. D. Denlinger, T. D. Moustakas, C. Heske
Chemical Structure Of Vanadium-Based Contact Formation On N-Ain, S. Pookpanratana, R. France, M. Blum, Sean R. Mulcahy, A. Bell, M. Bär, L. Weinhardt, Y. Zhang, T. Hofmann, O. Fuchs, W. Yang, J. D. Denlinger, T. D. Moustakas, C. Heske
Geology Faculty Publications
We have investigated the chemical interaction between a Au/V/Al/V layer structure and n-type AlN epilayers using soft x-ray photoemission, x-ray emission spectroscopy, and atomic force microscopy. To understand the complex processes involved in this multicomponent system, we have studied the interface before and after a rapid thermal annealing step. We find the formation of a number of chemical phases at the interface, including VN, metallic vanadium, aluminum oxide, and metallic gold. An interaction mechanism for metal contact formation on the entire n-Al,GaN system is proposed. ©
Uv Light-Induced Changes To The Surface Conduction In Hydrothermal Zno, B. Claflin, David C. Look
Uv Light-Induced Changes To The Surface Conduction In Hydrothermal Zno, B. Claflin, David C. Look
Physics Faculty Publications
High quality, bulk ZnO crystals grown by Tokyo Denpa using the hydrothermal process typically exhibit a room temperature carrier concentration in the 1013–1014 cm−3 range and a low mobility, conductive surface layer, observed at low temperature, with a sheet concentration on the order of 1012–1013 cm−2. In the sample discussed here, bulk conduction is controlled by two donor levels at 50 and 400 meV with concentrations of 1.2×1016 and 1.5×1016 cm−3, respectively. Temperature-dependent photo-Hall-effect measurements, using blue/UV light, in vacuum show an increase in the surface sheet …
In-Implanted Zno: Controlled Degenerate Surface Layer, David C. Look, Gary C. Farlow, F. Yaqoob, L. H. Vanamurthy, M. Huang
In-Implanted Zno: Controlled Degenerate Surface Layer, David C. Look, Gary C. Farlow, F. Yaqoob, L. H. Vanamurthy, M. Huang
Physics Faculty Publications
In was implanted into bulk ZnO creating a square profile with a thickness of about 100 nm and an In concentration of about 1×1020 cm-3. The layer was analyzed with Rutherford backscattering, temperature-dependent Hall effect, and low-temperature photoluminescence measurements. The implantation created a nearly degenerate carrier concentration n of about 2×1019 cm-3, but with a very low mobility μ, increasing from about 0.06 cm2/V s at 20 K to about 2 cm2/V s at 300 K. However, after annealing at 600 °C for 30 min, n increased to about 5×10 …
Enhanced Spin-Dependent Tunneling Magnetoresistance In Magnetite Films Coated By Polystyrene, Wendong Wang, Leszek Malkinski, Jinke Tang
Enhanced Spin-Dependent Tunneling Magnetoresistance In Magnetite Films Coated By Polystyrene, Wendong Wang, Leszek Malkinski, Jinke Tang
Physics Faculty Publications
Hematite films were deposited by magnetron sputtering. A phase transformation from hematite to magnetite occurred when polystyrene (PS) coated hematite films were annealed above 200 °C in hydrogen flow. Giant negative magnetoresistance (MR) was observed with the best MR ratio of over 8% (at room temperature and in a field of 5.5 T) found in samples annealed at 230 °C. The temperature dependence of the resistivity is characteristic of intergranular tunneling. After the PS layer was removed and the films annealed again at 230 °C in hydrogen flow, the resistivity increased by about one order of magnitude and the MR …
Stress Evolution In Nanocrystalline Diamond Films Produced By Chemical Vapor Deposition, Hao Li, Brian W. Sheldon, Abhishek Kothari, Zhigang Ban, Barbara L. Walden
Stress Evolution In Nanocrystalline Diamond Films Produced By Chemical Vapor Deposition, Hao Li, Brian W. Sheldon, Abhishek Kothari, Zhigang Ban, Barbara L. Walden
Faculty Scholarship
Nanocrystalline diamond films were grown on silicon substrates by microwave plasma enhanced chemical vapor deposition with 1% methane, 2%–10% hydrogen, and argon. High resolution transmission electron microscope images and selected area electron diffraction patterns confirm that the films consist of 10–20 nm sized diamond grains. The residual and intrinsic stresses were investigated using wafer curvature. Intrinsic stresses were always tensile, with higher H2 concentrations generally leading to higher stresses. Annealing the films in a hydrogen plasma significantly increased these stresses. These hydrogen induced changes also appear to alter stress levels and stress gradients during the growth process itself. Raman …
Compositional Stability Of Fept Nanoparticles On Sio2/Si During Annealing, Richard R. Vanfleet, B. Yao, R. V. Petrova, K. R. Coffey
Compositional Stability Of Fept Nanoparticles On Sio2/Si During Annealing, Richard R. Vanfleet, B. Yao, R. V. Petrova, K. R. Coffey
Faculty Publications
The loss of Fe due to oxidation or diffusion into the substrate can prevent the successful preparation of well-ordered, stoichiometric, FePt nanoparticles. In this work we report the composition changes during annealing observed for small (<10 nm) FePt nanoparticles on thermally grown SiO2 layers on Si wafer substrates. Additionally, we describe the use of a controlled reducing gas mixture, Ar+H2+H2O, to reduce the loss of Fe.
Electroabsorption Studies Of Structurally Modified Fullerene Thin Films, Gerald Farrell, Gordon Chambers, Hugh Byrne
Electroabsorption Studies Of Structurally Modified Fullerene Thin Films, Gerald Farrell, Gordon Chambers, Hugh Byrne
Conference papers
Ultraviolet (UV/Vis) and Electroabsorption (EA) spectroscopy is used to examine and differentiate between intermolecular and intra molecular excited state species in fullerene films. Charge Transfer (CT) states are identified at 2.4 eV and 2.7 eV and dipole moments are calculated. Thermal annealing of C60 films is monitored in situ using absorption spectroscopy and electroabsorption spectroscopy. Recorded spectra display both some temperature dependent and partially irreversible effects, indicating the occurrence of an annealing process. EA shows that the CT states associated with the transferring an electron from the HOMO of one molecule located at the (0,0,0) position to the LUMO of …
Electronic Structure And Light-Induced Conductivity Of A Transparent Refractory Oxide, Julia E. Medvedeva, Arthur J. Freeman, Mariana I. Bertoni, Thomas O. Mason
Electronic Structure And Light-Induced Conductivity Of A Transparent Refractory Oxide, Julia E. Medvedeva, Arthur J. Freeman, Mariana I. Bertoni, Thomas O. Mason
Physics Faculty Research & Creative Works
Combined first-principles and experimental investigations reveal the underlying mechanism responsible for a drastic change of the conductivity (by 10 orders of magnitude) following hydrogen annealing and UV irradiation in a transparent oxide, 12CaO · 7Al2O3, found by Hayashi et al. [Nature (London) 419, 462 (2002).] The charge transport associated with photoexcitation of an electron from H- occurs by electron hopping.We identify the atoms participating in the hops, determine the exact paths for the carrier migration, estimate the temperature behavior of the hopping transport, and predict a way to enhance the conductivity by specific doping.
Low‐Cost Technique For Preparing N‐Sb2S3/P‐Si Heterojunction Solar Cells, O. Savadogo, K. C. Mandal
Low‐Cost Technique For Preparing N‐Sb2S3/P‐Si Heterojunction Solar Cells, O. Savadogo, K. C. Mandal
Faculty Publications
No abstract provided.