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ZnO Heteroepitaxy on Sapphire Using a Novel Buffer Layer of Titanium Oxide: Optoelectronic Behavior  [PDF]
Satoshi Yamauchi, Yoh Imai
Crystal Structure Theory and Applications (CSTA) , 2013, DOI: 10.4236/csta.2013.23014
Abstract:

Optoelectronic property of ZnO epitaxial layer grown by plasma-assisted epitaxy at temperature as low as 340°C using Ti2O3 buffer layer on a-sapphire were studied by low temperature photoluminescence at 10 K comparing to the layers on c-sapphire and a-sapphire without the buffer layer. The near band-edge emission consisting of free-exciton emissions and neutral-donor bound exciton emissions was significantly dependent on the buffer thickness and dominated by the free-exciton emissions in the layer grown on the very thin buffer layer about 0.8 nm, whereas the intense emissions by neutral-donor bound excitons were observed in the ZnO layer on c-sapphire. The structural behavior indicated the donor was originated from the three-dimensional growth of ZnO layer and details of the optoelectronic feature suggested the residual donors were Al and interstitial-Zn.

A 1 W injection locked cw titanium:sapphire laser  [PDF]
E. A. Cummings,M. S. Hicken,S. D. Bergeson
Physics , 2001,
Abstract: We report an injection-locked cw titanium:sapphire ring laser at 846 nm. It produces 1.00 W in a single frequency when pumped with 5.5 W. Single frequency operation requires only a few milliwatts of injected power.
Response of Seven Crystallographic Orientations of Sapphire Crystals to Shock Stresses of 16 to 86 GPa  [PDF]
G. I. Kanel,W. J. Nellis,A. S. Savinykh,S. V. Razorenov,A. M. Rajendran
Physics , 2009, DOI: 10.1063/1.3204940
Abstract: Shock-wave profiles of sapphire (single-crystal Al2O3) with seven crystallographic orientations were measured with time-resolved VISAR interferometry at shock stresses in the range 16 to 86 GPa. Shock propagation was normal to the surface of each cut. The angle between the c-axis of the hexagonal crystal structure and the direction of shock propagation varied from 0 for c-cut up to 90 degrees for m-cut in the basal plane. Based on published shock-induced transparencies, shock-induced optical transparency correlates with the smoothness of the shock-wave profile. The ultimate goal was to find the direction of shock propagation in sapphire that is most transparent as a window. Particle velocity histories were recorded at the interface between a sapphire crystal and a LiF window. In most cases measured wave profiles are noisy as a result of heterogeneity of deformation. Measured values of Hugoniot Elastic Limits (HELs) depend on direction of shock compression and peak shock stress. The largest HEL values were recorded for shock loading along the c-axis and perpendicular to c along the m-direction. Shock compression along the m- and s-directions is accompanied by the smallest heterogeneity of deformation and the smallest rise time of the plastic shock wave. m- and s-cut sapphire most closely approach ideal elastic-plastic flow, which suggests that m- and s-cut sapphire are probably the orientations that remains most transparent to highest shock pressures. Under purely elastic deformation sapphire has very high spall strength, which depends on load duration and peak stress. Plastic deformation of sapphire causes loss of its tensile strength.
Structural and Crystallographic Features of Chemically Synthesized Cero- and Titanium Cero- Antimonates Inorganic Ion Exchangers and Its Applications  [PDF]
Mamdouh M. Abou-Mesalam
Advances in Chemical Engineering and Science (ACES) , 2011, DOI: 10.4236/aces.2011.11001
Abstract: Chemically synthesized cero-antimonate and titanium cero-antimonate prepared by sol-gel technique was conducted for the synthesis of a novel ion exchanger. The prepared materials has been characterized by X-ray diffraction, X-ray fluorescence, Fourier transform Infrared Spectroscopy (FT-IR) and Thermograve-metric analyses. The structures and empirical formula's was identified and found to CeSb4O12?6.19H2O and TiCeSb4O14?12.22H2O, for cero-antiomate and titanium cero-antimonate, respectively. The data obtained from X-ray diffraction was analyzed to define the crystallographic feature of cero-antimonate and titanium cero-antimonate and found both the composites were belong to cubic system with lattice constant 5.15 and 5.149 Å, respectively. The crystallite size and strain of cero-antimonate and titanium cero-antimonate were determined. By using ChemDraw Ultra program the modeling structures of cero-antimonate and titanium cero-antimonate were conducted. Finally, application of the prepared materials for the removal of heavy metals from industrial waste water in terms of capacity measurements was performed.
Phase-Locked, Low-Noise, Frequency Agile Titanium: Sapphire Lasers for Simultaneous Atom Interferometers  [PDF]
Holger Mueller,Sheng-wey Chiow,Quan Long,Steven Chu
Physics , 2005, DOI: 10.1364/OL.31.000202
Abstract: We demonstrate phase lock of two >1.6W Titanium:sapphire lasers with a phase noise of -138dBc/Hz at 1MHz from the carrier, using an intra-cavity electro-optic phase modulator. The residual phase variance is 2.5 10^(-8)rad^2 integrated from 1Hz to 10kHz. Instantaneous offset frequency steps of up to 4MHz are achieved within 200ns. Simultaneous atom interferometers can make full use of this ultra-low phase noise in differential measurements by suppressing common influences from vibration of optics.
Pulsed Laser Deposition of epitaxial titanium diboride thin films  [PDF]
V. Ferrando,D. Marre',P. Manfrinetti,I. Pallecchi,C. Tarantini,C. Ferdeghini
Physics , 2003, DOI: 10.1016/S0040-6090(03)01025-3
Abstract: Epitaxial titanium diboride thin films have been deposited on sapphire substrates by Pulsed Laser Ablation technique. Structural properties of the films have been studied during the growth by Reflection High Energy Electron Diffraction (RHEED) and ex-situ by means of X-ray diffraction techniques; both kinds of measurements indicate a good crystallographic orientation of the TiB2 film both in plane and along the c axis. A flat surface has been observed by Atomic Force Microscopy imaging. Electrical resistivity at room temperature resulted to be five times higher than the value reported for single crystals. The films resulted to be also very stable at high temperature, which is very promising for using this material as a buffer layer in the growth of magnesium diboride thin films.
Structure and growth of titanium buffer layers on Al2O3(0001)  [PDF]
E. Sondergard,O. Kerjan,C. Barreteau,J. Jupille
Physics , 2004, DOI: 10.1016/j.susc.2004.03.072
Abstract: The structure of titanium films on \alpha - Al2O3(0001) surfaces at room temperature was investigated through in situ reflection high energy electron diffraction (RHEED). The \alpha-phase of titanium was observed to grow with the Ti(0001) || Al2O3(0001), Ti[1100] || Al2O3[2110] and Ti[1010] || Al2O3[1100] epitaxy. For up to 6 nm thick films, an other structure was found to coexist with \alpha-Ti. Its presence has dramatic consequences for the wetting of silver, which partly explains the nontrivial buffer effect of titanium at the silver/alumina interface. From the RHEED data, the extra structure is assigned to the high-pressure hexagonal \omega-Ti phase. This is supported by tight-binding total energy calculations that demonstrate that the \omega phase could actually be stabilized by the \alpha - Al2O3(0001) substrate.
Surfactants in semiconductor heteroepitaxy: Thermodynamics and/or kinetics?  [PDF]
Ivan Markov
Physics , 2000,
Abstract: The effect of surfactants on the thermodynamics and kinetics of semiconductor heteroepitaxy is briefly discussed. It is argued that the way the surfactants suppress the thermodynamic driving force for 3D islanding depends on the mechanism of exchange of overlayer and surfactant atoms. If the overlayer atoms occupy bulk-like positions provided by the outgoing surfactant dimers, as is the case of Ge/Si(001), large atomic displacements are forcibly inhibited, and the wetting of the overlayer by the substrate becomes nearly complete. This complete wetting of the overlayer by the substrate means a zero thermodynamic driving force for 3D islanding. Once the thermodynamics do not require 3D islanding a change of the growth mode with the temperature should not be observed. Thus, the temperature change of the growth mode appears as an indication for the primary role of the kinetics, as in the case of Ge/Si(111).
ZnO Nanostructures Grown on AlN/Sapphire Substrates by MOCVD
ZnO Nanostructures Grown on A1N/Sapphire Substrates by MOCVD

WEI Hong-Yuan,HU Wei-Guo,ZHANG Pan-Feng,LIU Xiang-Lin,ZHU Qin-Sheng,WANG Zhan-Guo,
魏鸿源
,胡卫国,张攀峰,刘祥林,朱勤生,王占国

中国物理快报 , 2007,
Abstract: ZnO nanorods and nanotubes are successful synthesized on AlN/sapphire substrates by metal-organic chemical vapour deposition (MOCVD). The different morphology and structure properties of ZnO nanorods and nanotubes are found to be affected by the AlN under-layer. The photoluminescence spectra show the optical properties of the ZnO nanorods and nanotubes, in which a blueshift of UV emission is observed and is attributed to the surface effect.
Compared growth mechanisms of Zn-polar ZnO nanowires on O-polar ZnO and on sapphire  [PDF]
Guillaume Perillat-Merceroz,Robin Thierry,Pierre-Henri Jouneau,Pierre Ferret,Guy Feuillet
Physics , 2013, DOI: 10.1088/0957-4484/23/12/125702
Abstract: Controlling the growth of zinc oxide nanowires is necessary to optimize the performances of nanowire-based devices such as photovoltaic solar cells, nano-generators, or light-emitting diodes. In this view, we investigate the nucleation and growth mechanisms of ZnO nanowires grown by metalorganic vapor phase epitaxy either on O-polar ZnO or on sapphire substrates. Whatever the substrate, ZnO nanowires are Zn-polar, as demonstrated by convergent beam electron diffraction. For growth on O-polar ZnO substrate, the nanowires are found to sit on O-polar pyramids. As growth proceeds, the inversion domain boundary moves up in order to remain at the top of the O-polar pyramids. For growth on sapphire substrates, the nanowires may also originate from the sapphire / ZnO interface. The presence of atomic steps and the non-polar character of sapphire could be the cause of the Zn-polar crystal nucleation on sapphire, whereas it is proposed that the segregation of aluminum impurities could account for the nucleation of inverted domains for growth on O-polar ZnO.
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