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MgO-doped stoichiometric LiTaO3 (MgO:SLT) is one of the most promising nonlinear materials. However, its industrial application is limited by the poor optical quality caused by the nonhomogeneous distribution of magnesium. Herein, an MgO:SLT polycrystalline powder was synthesized with a homogenous magnesium distribution by a wet-chemical spray-drying method. A comparative investigation of the coordination state of Ta ions in MgO:SLT powders synthesized by this method and by a conventional solid-state reaction method was performed by X-ray photoelectron spectroscopy. It is proved that the Ta-Li antisite was completely eliminated as a result of the homogeneous Mg doping in the SLT lattice using the wet-chemical spray-drying method. However, for MgO:LT powder produced by the solid-state reaction method, element analysis after acid treatment shows that some Mg ions did not enter the LT lattice after high-temperature calcination. Also, scanning electron microscopy and transmission electron microscopy energy dispersive spectroscopy verified that some MgO particles still exist in the as-synthesized MgO:LT powder. This synthesis method can be used for mass production of high-quality polycrystalline powders for doped crystal growth and some other doped oxide powder products with high melt point. [ABSTRACT FROM AUTHOR]

As a demonstration of the activity modulation migration enhanced epitaxy (AM-MEE) heteroepitaxial 2H-AlN thin films of 53.8 nm and 171.3 nm thickness on Si(111) on a double buffer layer (DBL) have been grown by the AM-MEE of plasma assisted molecular beam epitaxy (PA-MBE) method. It is a droplet free growth and an atomic layer epitaxy (ALE). The influence of the DBL, which was formed in a MBE chamber before the AM-MEE growth of 2H-AlN thin films on Si(111), was studied to improve the crystallinity of AlN films. For the growth of high quality 2H-AlN on Si(111), the optimization of growth of the DBL. The interface roughness of the DBL as a layer between two layers of AlN and Si, AlN/DBL/Si was characterized by grazing incidence X-ray reflectivity (GIXR) and the surfaces were observed by AFM. Full width at half maximum (FWHM) of ω /2θ for 53.8 nm and 171.3 nm thickness AlN (0002) films were 12.1 arcmin and 7.1 arcmin, respectively. AFM images showed droplet free growth after the AM-MEE and importance of the preparation of initial clean Si surface. Unifrom formation of DBL on a large size wafer of Si was available to use indirect exposure of N radical atoms. By increasing the thickness of the AlN the crystallinity was improved but the surface roughness of AlN did not depend on the thickness of the AlN films obtained by fitting results of GIXR curves. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Reactive ion etching (RIE) is known to alter electrical characteristics by creating a damaged layer on the surface of the etched substance. An Au/p-Si Schottky diode was formed on a silicon surface which was etched by RE using CF4 gas. It was found that excess dc conductance and inductive susceptance were observed in the current voltage (I-V) and the admittance frequency (Y-f) characteristics under forward bias conditions, respectively. These results are expLained by assuming the existence of deep-level traps induced by RJE in the depletion region of the diode. Assuming a damage depth distribution of 10 nm, the experimental values of inductive susceptance are able to calculate by following parameters of the deep-level traps induced by RIE; Er Ev 0.33 (eV) and NT = 1 × 1019 (cm-3). [ABSTRACT FROM AUTHOR]

A radio frequency inductively coupled plasma (rf-ICP) nitrogen discharge was investigated to improve group III nitride growth on Si substrates. Two modes of the rf-ICP discharge, low brightness (LB) and high brightness (HB) discharges, were successfully controlled through mode transition. Direct irradiation and indirect irradiation of nitrogen atoms were applied for the growth of group III nitrides. As an application of indirect irradiation of nitrogen atoms, the growth of β-Si3N4 using interface reaction epitaxy (IRE) was studied. As applications of direct irradiation of nitrogen atoms, activity modulation migration-enhanced epitaxy (AM-MEE) and plasma-assisted molecular beam epitaxy (PA-MBE), which are atomic layer epitaxy (ALE) methods, are demonstrated. These growth systems operate to realize a single-growth process from a Si substrate to an AlN or GaN epitaxial layer, i.e., through preparation of a double buffer (DBL) layer of AlN/β-Si3N4/Si after the growth of IRE β-Si3N4 and IRE AlN. The electron emission due to the self-ionization of nitrogen atoms on a negatively biased electrode is demonstrated to measure in situ direct and indirect nitrogen atom fluxes during the growth. [ABSTRACT FROM AUTHOR]

Highlights: [•] A dense TiH2 layer is synthesized by a hydrogen free acid-hydrothermal method. [•] Hydrogen in a TiH2 layer synthesized can release at low temperature. [•] During the dehydrogenation process, there is no any intermediate phase forming. [•] We report a method of low-cost, low-risk and convenience toward productive TiH2. [Copyright &y& Elsevier]