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Full-Text Articles in Physics
As-Doped P-Type Zno Produced By An Evaporation/Sputtering Process, David C. Look, G. M. Renlund, R. H. Burgener, J. R. Sizelove
As-Doped P-Type Zno Produced By An Evaporation/Sputtering Process, David C. Look, G. M. Renlund, R. H. Burgener, J. R. Sizelove
Physics Faculty Publications
Strongly p-type ZnO is produced by the following sequence of steps: (1) evaporation of Zn3As2 on a fused-quartz substrate at 350 °C; and (2) sputtering of ZnO with substrate held at 450 °C. The electrical characteristics include: resistivity of 0.4 Ω cm, a mobility of 4 cm2∕V s, and a hole concentration of about 4×1018 cm−3. This resistivity is among the best (lowest) ever reported for p-type ZnO. Secondary-ion mass spectroscopic analysis gives an average As concentration about 5×1019 cm−3, and a simple one-band fit of the …
Micro-Auger Electron Spectroscopy Studies Of Chemical And Electronic Effects At Gan-Sapphire Interfaces, X. L. Sun, S. T. Bradley, G. H. Jessen, David C. Look, Richard J. Molnar, L. J. Brillson
Micro-Auger Electron Spectroscopy Studies Of Chemical And Electronic Effects At Gan-Sapphire Interfaces, X. L. Sun, S. T. Bradley, G. H. Jessen, David C. Look, Richard J. Molnar, L. J. Brillson
Physics Faculty Publications
We have used cross-sectional micro-Auger electron spectroscopy (AES), coupled with micro-cathodoluminescence (CLS) spectroscopy, in a UHV scanning electron microscope to probe the chemical and related electronic features of hydride vapor phase epitaxy GaN/sapphire interfaces on a nanometer scale. AES images reveal dramatic evidence for micron-scale diffusion of O from Al2O3 into GaN. Conversely, plateau concentrations of N can extend microns into the sapphire, corresponding spatially to a 3.8 eV defect emission and Auger chemical shifts attributed to Al-N-O complexes. Interface Al Auger signals extending into GaN indicates AlGaN alloy formation, consistent with a blue-shifted CLS local interface …
Response Of The Martian Thermosphere/Ionosphere To Enhanced Fluxes Of Solar Soft X Rays, Jane L. Fox
Response Of The Martian Thermosphere/Ionosphere To Enhanced Fluxes Of Solar Soft X Rays, Jane L. Fox
Physics Faculty Publications
We have investigated the response of the thermosphere and ionosphere of Mars to enhanced fluxes of solar soft X rays, such as those that have been detected by the SNOE satellite (e.g., Bailey et al., 2000 ). We have constructed standard models by adopting the SC#21REFW and F79050N solar fluxes from H. E. Hinteregger (private communication) (see also Torr et al., 1979 ) for the low and high solar activity models, respectively. We then constructed enhanced soft X-ray models by multiplying the solar photon fluxes for wavelengths below 200 Å by a factor of 3 at low solar …
Below Band Gap Photoreflectance Transitions In Epitaxial Gan, Phil W. Yu, Jerry D. Clark, David C. Look, C. Q. Chen, Jinwei Yang, Edmundas Koutstis, M. Asif Khan, Denis V. Tsvertkov, Vladimir A. Dmitriev
Below Band Gap Photoreflectance Transitions In Epitaxial Gan, Phil W. Yu, Jerry D. Clark, David C. Look, C. Q. Chen, Jinwei Yang, Edmundas Koutstis, M. Asif Khan, Denis V. Tsvertkov, Vladimir A. Dmitriev
Physics Faculty Publications
A photoreflectance (PR) and photoluminescence (PL) study has been performed on a Si-doped epitaxial GaN layer that contains impurity or defect related below band gap features in its PR spectrum. In the 300 K PR spectrum, these features appear at energies of 3.26 and 3.33 eV, respectively, but below 180 K they can no longer be seen. The 3.26 eV line evidently corresponds to a donor acceptor pair transition, also seen in PL. The origin of the 3.33 eV line is uncertain, but may correspond to a transition involving the nitrogen vacancy.
Co2+ Dissociative Recombination: A Source Of Thermal And Nonthermal C On Mars, Jane L. Fox
Co2+ Dissociative Recombination: A Source Of Thermal And Nonthermal C On Mars, Jane L. Fox
Physics Faculty Publications
CO2 + dissociative recombination has been assumed in the past to proceed overwhelmingly by the channel that produces CO + O. Although the channel that leads to the products C + O2 is energetically possible, the significant rearrangement of bonds that is required has led to the belief that this channel contributes minimally. Seiersen et al. [2003] have recently measured the branching ratio for the latter channel, and they have reported a value of ∼9% of the total. We have constructed both low and high solar activity models of the Martian thermosphere, and we have tested the effect …
Hot Carbon Densities In The Exosphere Of Venus, Michael W. Liemohn, Jane L. Fox, Andrew F. Nagy, Xiaohua Fang
Hot Carbon Densities In The Exosphere Of Venus, Michael W. Liemohn, Jane L. Fox, Andrew F. Nagy, Xiaohua Fang
Physics Faculty Publications
The results of calculations of hot carbon densities in the exosphere of Venus are presented. The calculation is a two-step process. First a two-stream transport code is used to solve for the distribution function at the exobase, and then these results are used in a Liouville equation solution above the exobase. It is found that generally, photodissociation of carbon monoxide is the largest source of hot carbon atoms in the upper atmosphere of Venus, larger than dissociative recombination of CO+ and significantly larger than the creation of hot carbon through collisions with hot oxygen atoms. It is also found …
Anomalous Capture And Emission From Internal Surfaces Of Semiconductor Voids: Nanopores In Sic, David C. Look, Z-Q. Fang, S. Soloviev, T. S. Sudarshan, J. J. Boeckl
Anomalous Capture And Emission From Internal Surfaces Of Semiconductor Voids: Nanopores In Sic, David C. Look, Z-Q. Fang, S. Soloviev, T. S. Sudarshan, J. J. Boeckl
Physics Faculty Publications
Deep level transient spectroscopy in nanoporous, n-type SiC reveals a new type of deep (˜0.8 eV) trap that can hold more than 100 electrons and that has anomalous capture and emission behavior. Here we quantitatively explain these effects with a new, general formalism that treats both emission and capture in the presence of dynamic energy barriers, resulting from the charging and discharging of states on the internal surfaces of voids, such as pores or nanopipes. The capture kinetics display a logarithmic time dependence over a certain filling range, as has often been observed in connection with dislocation-related trapping.
Reply To "Comment On 'Recombination Of Excitons Bound To Oxygen And Silicon Donors In Freestanding Gan' ", A. Wysmolek, K. P. Korona, R. Stepniewski, J. M. Baranowsky, J. Bloniarz, M. Potemski, R. L. Jones, David C. Look, J. Kuhl, Seong-Ju S. Park, S. K. Lee
Reply To "Comment On 'Recombination Of Excitons Bound To Oxygen And Silicon Donors In Freestanding Gan' ", A. Wysmolek, K. P. Korona, R. Stepniewski, J. M. Baranowsky, J. Bloniarz, M. Potemski, R. L. Jones, David C. Look, J. Kuhl, Seong-Ju S. Park, S. K. Lee
Physics Faculty Publications
In their Comment on our publication [Phys. Rev. B 66, 245317 (2002)], Freitas et al. criticize our identification of donor-bound exciton transitions and the analysis of two-electron satellite emission lines. We show that some arguments given in the Comment are in conflict with our time-resolved and magneto-optical data. We present a discussion of the intradonor transition energies and donor chemical shifts to avoid misunderstanding.
Remote Hydrogen Plasma Doping Of Single Crystal Zno, Yuri M. Strzhemechny, Howard L. Mosbacker, David C. Look, Donald C. Reynolds, Cole W. Litton, Nelson Y. Garces, Nancy C. Giles, Larry E. Halliburton, Shigeru Niki, Leonard J. Brillson
Remote Hydrogen Plasma Doping Of Single Crystal Zno, Yuri M. Strzhemechny, Howard L. Mosbacker, David C. Look, Donald C. Reynolds, Cole W. Litton, Nelson Y. Garces, Nancy C. Giles, Larry E. Halliburton, Shigeru Niki, Leonard J. Brillson
Physics Faculty Publications
We demonstrate that remote plasma hydrogenation can increase electron concentrations in ZnO single crystals by more than an order of magnitude. We investigated the effects of this treatment on Hall concentration and mobility as well as on the bound exciton emission peak I4 for a variety of ZnO single crystals–bulk air annealed, Li doped, and epitaxially grown on sapphire. Hydrogen increases I4 intensity in conducting samples annealed at 500 and 600 °C and partially restores emission in the I4 range for Li-diffused ZnO. Hydrogenation increases carrier concentration significantly for the semi-insulating Li doped and epitaxial thin film …
High-Quality, Melt-Grown Zno Single Crystals, D. C. Reynolds, C. W. Litton, David C. Look, J. E. Joelscher, B. Claflin, T. C. Collins, J. Nause, B. Nemeth
High-Quality, Melt-Grown Zno Single Crystals, D. C. Reynolds, C. W. Litton, David C. Look, J. E. Joelscher, B. Claflin, T. C. Collins, J. Nause, B. Nemeth
Physics Faculty Publications
High-quality, melt-grown ZnO crystals are reported. The reflection and emission spectra of the melt-grown samples are compared with the same spectra from high-quality, vapor-grown ZnO crystals. We isolate the reflection and emission spectra predominantly related to the intrinsic properties associated with the wurtzite structure of the crystals. The quality of the crystals is reflected in the spectral reproduction of the intrinsic properties of the crystals. Both the ground state and the n=2 state of the free excitons associated with the A, B, and C valence bands of the crystals are spectrally observed in reflection. Assuming a hydrogenic character for …