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Full-Text Articles in Physics
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 …
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 …
Electron And Hole Traps In N-Doped Zno Grown On P-Type Si Substrate By Mocvd, Zhaoqiang Fang, Bruce B. Claflin, David C. Look, Lei L. Kerr, Xiaonan Li
Electron And Hole Traps In N-Doped Zno Grown On P-Type Si Substrate By Mocvd, Zhaoqiang Fang, Bruce B. Claflin, David C. Look, Lei L. Kerr, Xiaonan Li
Physics Faculty Publications
Electron and hole traps in N-doped ZnO were investigated using a structure of n+-ZnO:Al/i-ZnO/ZnO:N grown on a p-Si substrate by metalorganic chemical vapor deposition (for growth of the ZnO:N layer) and sputtering deposition (for growth of the i-ZnO and n+-ZnO:Al layers). Current-voltage and capacitance-voltage characteristics measured at temperatures from 200 to 400 K show that the structure is an abrupt n+−p diode with very low leakage currents. By using deep level transient spectroscopy, two hole traps, H3 (0.35 eV) and H4 (0.48 eV), are found in the p-Si …
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 …
Chemistry-Induced Intrinsic Stress Variations During The Chemical Vapor Deposition Of Polycrystalline Diamond, Ashok Rajamani, Brian W. Sheldon, Sumit Nijhawan, Alan Schwartzman, Janet Rankin, Barbara L. Walden, Laura Riester
Chemistry-Induced Intrinsic Stress Variations During The Chemical Vapor Deposition Of Polycrystalline Diamond, Ashok Rajamani, Brian W. Sheldon, Sumit Nijhawan, Alan Schwartzman, Janet Rankin, Barbara L. Walden, Laura Riester
Faculty Scholarship
Intrinsic tensile stresses in polycrystalline films are often attributed to the coalescence of neighboring grains during the early stages of film growth, where the energy decrease associated with converting two free surfaces into a grain boundary provides the driving force for creating tensile stress. Several recent models have analyzed this energy trade off to establish relationships between the stress and the surface∕interfacial energy driving force, the elastic properties of the film, and the grain size. To investigate these predictions, experiments were conducted with diamond films produced by chemical vapor deposition. A multistep processing procedure was used to produce films with …
Hopping Conduction In Molecular Beam Epitaxial Gaas Grown At Very Low Temperatures, David C. Look, Z-Q. Fang, J. W. Look, J. R. Sizelove
Hopping Conduction In Molecular Beam Epitaxial Gaas Grown At Very Low Temperatures, David C. Look, Z-Q. Fang, J. W. Look, J. R. Sizelove
Physics Faculty Publications
Conductivity and Hall effect measurements have been performed on 2 μm thick molecular beam epitaxial layers grown at very low substrate temperatures, 200 to 400°C. For growth temperatures below 300°C, the conduction is dominated by hopping between arsenic antisite defects of concentrations up to 1020 cm−3. Below measurement temperatures of about 130 K, the hopping conduction can be quenched by strong IR light illumination, because the antisite then becomes metastable. The antisite has a thermal activation energy of , and thus is not identical to the famous EL2. Both nearest‐neighbor and variable‐range hopping mechanisms are considered in …