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- 1. Phys. Rev. Lett. 102, 075506 (2009) , “Proton Tunneling: A Decay Channel of the O-H Stretch Mode in KTaO3”, E. J. Spahr, L. Wen, M. Stavola, L. A. Boatner, L. C. Feldman, N. H. Tolk, and G. LüpkeThe vibrational lifetimes of the O-H and O-D stretch modes in the perovskite oxide KTaO3 are measured by pump-probe infrared spectroscopy. Both stretch modes are exceptionally long lived and exhibit a large “reverse” isotope effect, due to a phonon-assisted proton-tunneling process, which involves the O-Ta-O bending motion. The excited-state tunneling rate is found to be 7 orders of magnitude larger than from the ground state in the proton conducting oxide, BaCeO3 [Phys. Rev. B 60, R3713 (1999)]. (Read more)
- 2. J.Am.Chem.Soc. 130, 48 (2008) , ACS , “Enhanced Ferromagnetism and Tunable Saturation Magnetization of Mn/C Codoped GaN Nanostructures Synthesized by Carbothermal Nitridation”, Zeyan Wang, Baibiao Huang, Lin Yu, Ying Dai, Peng Wang, Xiaoyan Qin, Xiaoyang Zhang, Jiyong Wei, Jie Zhan, Xiangyang Jing, Haixia Liu, and Myung-Hwan WhangboMn/C-codoped GaN nanostructures were synthesized by carbothermal nitridation with active charcoal as the carbon source. Nanostructures such as zigzag nanowires and nanoscrews were observed by varying the reaction time and the C/Ga molar ratio of the starting material used for the synthesis. The structures and morphologies of the as-grown samples were characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy measurements. The doping of both Mn and C in the GaN matrix was confirmed by X-ray photoelectron spectroscopy measurements, and the ferromagnetic properties of Mn/C-codoped GaN samples were confirmed by room-temperature magnetization measurements. The saturation magnetization of Mn/C-codoped GaN increases steadily with increasing C/Ga molar ratio of the starting material at a rate of ~0.023 emu/g per C/Ga molar ratio, and the ferromagnetism of Mn/C-codoped GaN can be stronger than that of Mn-doped GaN by a factor of ~40. A plausible growth mechanism was proposed, and the role of carbon codoping in tuning the morphology and ferromagnetic property was discussed. Our work suggests that carbon doping in the GaN matrix favors the N sites over the Ga sites, Mn/C-codoping in the GaN matrix is energetically favorable, and the C-codoping strongly enhances the preference of the FM coupling to the AFM coupling between the two doped Mn sites. These suggestions were probed on the basis of first-principles density functional theory electronic structure calculations for a number of model doped structures constructed with a 32-atom 2 × 2 × 2 supercell. (Read more)
- 3. Phys. Rev. B 75, 195207 (2007) , “Effects of optical absorption on 71Ga optically polarized NMR in semi-insulating GaAs: Measurements and simulations”, Stacy Mui, Kannan Ramaswamy, and Sophia E. HayesThe intensity and the hyperfine shift of optically polarized NMR (OPNMR) signals of 71Ga in semi-insulating GaAs have been found to depend on the photon energy and the helicity of light used for optical pumping. Single-crystal GaAs wafers of two different thicknesses, 400 and 175 ... (Read more)
- 4. Phys. Rev. B 75, 085415 (2007) , “Positronium as a probe of transient paramagnetic centers in a-SiO2”, D. B. Cassidy, K. T. Yokoyama, S. H. M. Deng, D. L. Griscom, H. Miyadera, H. W. K. Tom, C. M. Varma, and A. P. Mills, Jr.A laser-pump, positron-probe technique has been developed for measuring the dynamics of laser-induced paramagnetic centers in porous materials. The basis of the technique is the fact that the annihilation rate of ortho-positronium may increase in the presence of unpaired spins. By using an intense... (Read more)
- 5. Phys. Rev. Lett. 98, 206406 (2007) , “Role of Intermolecular Coupling in the Photophysics of Disordered Organic Semiconductors: Aggregate Emission in Regioregular Polythiophene”, Jenny Clark, Carlos Silva, Richard H. Friend, and Frank C. SpanoWe address the role of excitonic coupling on the nature of photoexcitations in the conjugated polymer regioregular poly(3-hexylthiophene). By means of temperature-dependent absorption and photoluminescence spectroscopy, we show that optical emission is overwhelmingly dominated by weakly coupled H... (Read more)
- 6. Phys. Rev. Lett. 98, 026802 (2007) , “Microscopic Basis for the Mechanism of Carrier Dynamics in an Operating p-n Junction Examined by Using Light-Modulated Scanning Tunneling Spectroscopy”, Shoji Yoshida, Yuya Kanitani, Ryuji Oshima, Yoshitaka Okada, Osamu Takeuchi, and Hidemi ShigekawaThe doping characteristics and carrier transport in a GaAs p-n junction were visualized with a ~10 nm spatial resolution, using light-modulated scanning tunneling spectroscopy. The dynamics of minority carriers under operating conditions, such as recombination, diffusion, and electric... (Read more)
- 7. Appl. Phys. Lett. 89, 101111 (2006) , “Investigation of dark line defects induced by catastrophic optical damage in broad-area AlGaInP laser diodes”, M. Bou Sanayeh, A. Jaeger, W. Schmid, S. Tautz, P. Brick, K. Streubel, and G. BacherThe authors present a detailed investigation of defects generated during catastrophic optical damage (COD) in high-power 650 nm AlGaInP lasers using microphotoluminescence (µ-PL) mapping, focused ion beam (FIB) microscopy, and deep-etching techniques. High-resolution µ-PL... (Read more)
- 8. Appl. Phys. Lett. 89, 092103 (2006) , “Electron energy barriers at interfaces of GaAs(100) with LaAlO3 and Gd2O3”, V. V. Afanas'ev, A. Stesmans, R. Droopad, M.Passlack, L.F. Edge, D. G. SchlomElectron energy barriers at the interfaces of GaAs(100) with Gd2O3 appear to be insensitive to the Fermi level pinning indicating that charges at interface states are of marginal importance for the band alignment at semiconductor/insulator interfaces. The inferred conduction... (Read more)
- 9. Appl. Phys. Lett. 88, 161905 (2006) , “Defect characterization of Si-doped GaN films by a scanning near-field optical microscope-induced photoluminescence”, M. Yoshikawa, R. Sugie, M. Murakami, T. Matsunobe, K. Matsuda, and H. IshidaWe developed a tapping-mode-scanning near-field optical microscope to measure near-field photoluminescence (SNOM-PL) with nanometer spatial resolution using an ultraviolet laser, and we measured the defect distribution of a Si-doped GaN film. The obtained result was compared with one measured by... (Read more)
- 10. J. Appl. Phys. 100, 104901 (2006) , “Photoluminescence and photoconductivity in CdTe crystals doped with Bi”, E. Saucedo, C. M. Ruiz, V. Bermúdez, E. Dieguez, E. Gombia, A. Zappettini, A. Baraldi, and N. V. SochinskiiDefect levels in CdTe doped with Bi are studied by low temperature photoluminescence, photoinduced current transient spectroscopy, photoconductivity measurements, and optical absorption. Two centers associated with the doping with Bi are reported. The first one, a deep level located at... (Read more)
- 11. J. Appl. Phys. 100, 093507 (2006) , “A view of the implanted SiC damage by Rutherford backscattering spectroscopy, spectroscopic ellipsometry, and transmission electron microscopy”, G. Battistig, N. Q. Khánh, P. Petrik, T. Lohner, L. Dobos, B. Pécz, J. García López, and Y. Morilla4H-SiC single crystalline substrates were implanted at room temperature with 150 keV Al+ ions using fluences of 4×1014, 1×1015, and 2×1015 cm−2 with current density of 2.5 µA cm−2.... (Read more)
- 12. J. Appl. Phys. 100, 083512 (2006) , “Spectroscopy and optically stimulated luminescence of Al2O3:C using time-resolved measurements”, E. G. Yukihara and S. W. S. McKeeverThis paper reports the observation of ultraviolet (UV) emission at 335 nm in the optically stimulated luminescence (OSL) of carbon-doped aluminum oxide (Al2O3:C) and presents results on the investigation of the OSL properties of this band, including its dose response, time... (Read more)
- 13. J. Appl. Phys. 100, 043706 (2006) , “Electrical properties of unintentionally doped semi-insulating and conducting 6H-SiC”, W. C. Mitchel, W. D. Mitchell, Z. Q. Fang, D. C. Look, S. R. Smith, H. E. Smith, Igor Khlebnikov, Y. I. Khlebnikov, C. Basceri, and C. BalkasTemperature dependent Hall effect (TDH), low temperature photoluminescence (LTPL), secondary ion mass spectrometry (SIMS), optical admittance spectroscopy (OAS), and thermally stimulated current (TSC) measurements have been made on 6H-SiC grown by the physical vapor transport technique... (Read more)
- 14. J. Appl. Phys. 100, 033517 (2006) , “Sources of optical absorption between 5.7 and 5.9 eV in silica implanted with Si or O”, R. H. Magruder, III, A. Stesmans, K. Clémer, R. A. Weeks, and R. A. WellerTo determine if the only source of optical absorption between 5.8 and 5.9 eV is the E center (absorbing at 5.85 eV) two separate suites of type III silica samples were implanted, one with Si and one with O. Several ion energies were used for implantation to produce layers 600 and... (Read more)
- 15. J. Appl. Phys. 100, 013501 (2006) , “Contactless electromodulation spectroscopy of AlGaN/GaN heterostructures with a two-dimensional electron gas: A comparison of photoreflectance and contactless electroreflectance”, R. Kudrawiec, M. Syperek, M. Motyka, J. Misiewicz, R. Paszkiewicz, B. Paszkiewicz, M. T?acza?aPhotoreflectance (PR) and contactless electroreflectance (CER) spectroscopies have been applied to study optical transitions in undoped and Si-doped AlGaN/GaN heterostructures at room temperature. Spectral features related to excitonic and band-to-band absorptions in GaN layer and band-to-band... (Read more)
- 16. J. Appl. Phys. 99, 123514 (2006) , “Study of the annealing kinetic effect and implantation energy on phosphorus-implanted silicon wafers using spectroscopic ellipsometry”, Emmanouil Lioudakis, Constantinos Christofides, and Andreas OthonosIn this work, we have studied the changes in the optical properties on crystalline silicon implanted wafers (1×10131×1016 P+/cm2) using an extensive ellipsometric analysis. The effects of implantation energy (20180 KeV) and... (Read more)
- 17. J. Appl. Phys. 99, 113520 (2006) , “Effects of hydrogen bond redistribution on photoluminescence of a-SiC:H films under thermal treatment”, A. V. Vasin, S. P. Kolesnik, A. A. Konchits, V. I. Kushnirenko, V. S. Lysenko, A. N. Nazarov, A. V. Rusavsky, and S. AshokHydrogenated amorphous silicon carbide (a-SiC:H) films have been deposited using magnetron sputtering technique. An integrated investigation of the effect of vacuum annealing temperature on photoluminescence properties and paramagnetic defects and its correlation with structural... (Read more)
- 18. J. Appl. Phys. 99, 073709 (2006) , “Optical and electron paramagnetic resonance spectroscopies of diffusion-doped Co2+:ZnSe”, Ming Luo, N. Y. Garces, N. C. Giles, Utpal N. Roy, Yunlong Cui, and Arnold BurgerThe efficacy of diffusing cobalt into window-grade polycrystalline ZnSe during high-temperature anneals has been studied. Absorption, photoluminescence (PL), time-resolved PL, and electron paramagnetic resonance (EPR) were used to characterize samples with cobalt concentrations ranging from... (Read more)
- 19. J. Phys. Chem. Solids 67, 789 (2006) , “Spectroscopic and magnetic studies of manganese ions in ZnO–Sb2O3–B2O3 glass system”, M. Srinivasa Reddy, G. Murali Krishna , N. VeeraiahZnO–Sb2O3–B2O3 glasses containing different concentrations of MnO ranging from 0 to 1.0 mol% were prepared. A number of studies, viz. optical absorption, infrared and ESR spectra and magnetic susceptibility, were carried out as a function of manganese ion concentration. The analysis of... (Read more)
- 20. Phys. Rev. B 74, 235210 (2006) , “Dislocation-induced deep electronic states in InP: Photocapacitance measurements”, Yutaka Oyama, Jun-ichi Nishizawa, Toshihiro Kimura, and Takenori TannoPhotocapacitance and excitation photocapacitance methods were applied to reveal the dislocation-induced deep levels in coalescent epitaxial lateral overgrowth layers of InP. Point-contact Schottky barrier junctions with small junction areas were formed on dislocated and dislocation-free regions by... (Read more)
- 21. Phys. Rev. B 74, 165202 (2006) , “Structural and electronic properties of Fe3+ and Fe2+ centers in GaN from optical and EPR experiments”, E. Malguth, A. Hoffmann, W. Gehlhoff, O. Gelhausen, M. R. Phillips, and X. XuThis work provides a consistent picture of the structural, optical, and electronic properties of Fe-doped GaN. A set of high-quality GaN crystals doped with Fe at concentrations ranging from 5×1017 cm3 to 2×1020 cm3 is... (Read more)
- 22. Phys. Rev. B 74, 153201 (2006) , “Light-induced hyperfine 69Ga shifts in semi-insulating GaAs observed by optically polarized NMR”, Kannan Ramaswamy, Stacy Mui, and Sophia E. HayesWe report the observation of 69Ga NMR light induced hyperfine shifts at 6 K in semi-insulating GaAs detected by optically polarized nuclear magnetic resonance in a magnetic field of 4.7 T. The main features of the observed shift are a systematic change in the absolute shift value as the... (Read more)
- 23. Phys. Rev. B 73, 245207 (2006) , “Photoionization measurement of deep defects in single-crystalline CVD diamond using the transient-current technique”, J. Isberg, A. Tajani, and D. J. TwitchenWe have adopted the transient-current technique as a sensitive method to detect small concentrations of charged defects in diamond and to study its photoionization spectrum. It is found that ionized impurity concentrations in the interval 1091013 cm3 can... (Read more)
- 24. Phys. Rev. Lett. 97, 227401 (2006) , “Optical Detection and Ionization of Donors in Specific Electronic and Nuclear Spin States”, A. Yang, M. Steger, D. Karaiskaj, M. L. W. Thewalt, M. Cardona, K. M. Itoh, H. Riemann, N. V. Abrosimov, M. F. Churbanov, A. V. Gusev, A. D. Bulanov, A. K. Kaliteevskii, O. N. Godisov, P. Becker, H.-J. Pohl, J. W. Ager III, and E. E. HallerWe resolve the remarkably sharp bound exciton transitions of highly enriched 28Si using a single-frequency laser and photoluminescence excitation spectroscopy, as well as photocurrent spectroscopy. Well-resolved doublets in the spectrum of the 31P donor reflect the hyperfine... (Read more)
- 25. Phys. Rev. Lett. 96, 145501 (2006) , “Identification of the Carbon Antisite-Vacancy Pair in 4H-SiC”, T. Umeda, N. T. Son, J. Isoya, E. Janzn, T. Ohshima, N. Morishita, H. Itoh, A. Gali, M. BockstedteThe metastability of vacancies was theoretically predicted for several compound semiconductors alongside their transformation into the antisite-vacancy pair counterpart; however, no experiment to date has unambiguously confirmed the existence of antisite-vacancy pairs. Using electron paramagnetic resonance and first principles calculations we identify the SI5 center as the carbon antisite-vacancy pair in the negative charge state (CSiVC-) in 4H-SiC. We suggest that this defect is a strong carrier-compensating center in n-type or high-purity semi-insulating SiC. (Read more)SiC| ENDOR EPR Theory electron-irradiation optical-spectroscopy thermal-meas./anneal-exp.| -1 -2 1.0eV~ 13C 29Si C1h C3v Carbon Csi EI5/6 HEI1 HEI5/6 Nitrogen P6/7 SI5 Silicon Vc antisite bistable/metastable dangling-bond n-type pair(=2) semi-insulating vacancy .inp files: SiC/SI5_C1h SiC/SI5_80K SiC/SI5_100K | last update: Takashi Fukushima
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