Papers by Keyword: Point Defect

Abstract: We have investigated the electrical properties of germanium-implanted n-type 4H-SiC epitaxial layers. Deep level transient spectroscopy (DLTS) was employed in order to study the influence of germanium ions on implantation-induced point defects. In particular, we observe a decrease of the concentration of Z_1/2 defect with increasing dose of implanted germanium.

Abstract: Triple-defect formation in B2-ordered binary A-B intermetallic compounds results fromthe asymmetry between the formation energies of A- and B-antisite defects. Chemical disorderingin such systems is strictly correlated with vacancy formation, which is the reason for usually veryhigh vacancy concentration. Consequently, Kinetic Monte Carlo (KMC) simulation of processes occurringin the triple-defect systems and controlled by atomic migration via vacancy mechanism mustinvolve complete vacancy thermodynamics – i.e. the simulated system must contain the equilibriumtemperature-dependent number of vacancies. The fully consistent approach based on two differentMonte Carlo techniques has been applied in the present study. The AB intermetallic was modelled withan Ising-type Hamiltonian and KMC simulated for “order-order” kinetics with temperature-dependentequilibrium number of vacancies previously determined by means of Semi Grand Canonical MonteCarlo (SGCMC) simulations. The procedure required in addition the determination of saddle -pointenergies assigned to particular atomic jumps to nn vacancies. Their values were estimated in relationto the nn pair-interaction energies with reference to Molecular Statics simulations performed for NiAlsystem with EAM energetics. The results elucidated the role of triple-defect formation as the atomisticscaleorigin of the experimentally observed surprisingly low rate of the “order-order” kinetics in bulkNiAl.

Abstract: Effects of high-speed deformation on age hardening and microstructural evolution behavior of 6061 aluminum alloys were studied. By affecting the high-speed impact compression (about 5 GPa) to the 6061 aluminum alloy plate in the state of quenching after the solution heat treatment, the maximum hardness became twice as high as the original hardness. Even after the impact compression, age-hardening was clearly identified both at 175 °C and 100 °C. TEM observation revealed that point defect clusters were distributed densely inside grains after the impact compression, possibly due to the effect of high-speed deformation. The point defect clusters observed were assumed to be stacking fault tetrahedra on the basis of high resolution TEM analysis. The point defect clusters and precipitates were both visible even after the peak-aged condition at 175 °C. The 6061 aluminum alloy specimen after the solution heat treatment, followed by the impact compression (8.0 GPa) and the peak-aged condition showed the highest hardness value (154 Hv) among the testing conditions selected in the present study.

Abstract: Well addressable and controllable point defects in device friendly semiconductors are desired for quantum computational and quantum informational processes. Recently, such defect, an ultra-bright single photon emitter, the antisite carbon carbon vacancy pair, was experimentally investigated in 4H-SiC. In our theoretical work, based on ab initio calculation and group theory analysis, we provide a deeper understanding of the features of the electronic structures and the luminescence process of this defect.

Abstract: A total of nine electrically active levels have been detected in as-grown and electron irradiated p-type 4H-SiC epilayers. These traps are found in the 0.32-2.26 eV energy range, above the valence band edge (E_V). Of these, six are majority carrier traps whereas three are minority carrier traps. We found that thermal oxidation affects the concentrations of two midgap levels, the majority carrier trap, labeled HK4 and the minority carrier trap identified as EH_6/7. The analysis of the irradiation energy and dose dependence of the concentration of these two traps, rules out the possibility that they may share the same origin.

Abstract: In order to filter, we use the coupling methods of line defects and point defects in photonic crystals to verity through theories and experimentations, get micro-cavity center frequency and wavelength of the main waveguide frequency resonance, and the same frequency lights will enter micro-cavity. Results show waveguides and micro-cavity can support its modes within in their deficiencies, but defects still can transfer energies through the evanescent coupling, the evanescent coupling is the role of the photonic crystals to the integration of device.

Abstract: The aim of this work is study of point defects modification in silicon dioxide by a high power density electron beam. In this work we used the method which allows to estimate quantitative content of luminescent point defects by dependence of cathodoluminescence on current density. Content of point defects was evaluated and changing of point defect content in silicon dioxide under electron beam was assessed. It is shown that content of defect connected with silicon deficit decreases whereas content of defect connected with oxygen deficit increases. The model of point defects transformation was suggested on the basis of these results.

Abstract: Irradiation induced complexes of C-rich case in silicon crystal were examined by the highly sensitive and accurate infrared absorption spectroscopy. Low impurity concentration and high quality crystal was used and low dose was employed to make the reaction simple. Almost all possible absorption lines were revealed and their absorbance determined. The conversion coefficient from absorbance to the complex concentration was estimated by the plausible assumptions. The reaction was discussed in terms of concentration rather than absorbance. Intra-group reaction, chain reaction of successive addition of oxygen or self-interstitial, reaction yield and competition between the parallel reactions were described.

Abstract: For the development of the crystal pulling process for 450 mm-diameter defect-free Si crystals, the impact of thermal stress on intrinsic point defect behavior during crystal growth is studied using extensive density functional theory calculations. The impact of thermal stress on the so-called Voronkov criterion and on void formation is clarified and compared with published experimental results.

Abstract: Unintentionally doped GaSb films grown by Molecular Beam Epitaxy (MBE) on GaAs (001) substrates were annealed under different temperatures and time. It was found that the rapid thermal annealing (RTA) process can improve the optical properties. By changing annealing temperature and time, the optimized annealing temperature and times are found to be 650°C and 30s, respectively. Point defects and dislocations are two major kinds of defect in undoped GaSb thin films grown by MBE on GaAs (001) substrates.