Search results for "Crystallographic"
showing 10 items of 202 documents
Low-temperature positron-lifetime studies of proton-irradiated silicon
1990
The positron-lifetime technique has been used to identify defects created in high-purity single-crystal silicon by irradiation with 12-MeV protons at 15 K, and the evolution of the defects has been studied by subsequent annealings between 20 and 650 K. Two clear annealing steps were seen in the samples, the first starting at 100 K and the other at 400 K. The first is suggested to be a result of the migration of free, negatively charged monovacancies, and the second is connected to the annealing of some vacancy-impurity complexes, probably negatively charged vacancy-oxygen pairs. The specific trapping rate of positrons to both of these negatively charged monovacancy-type defects has been fou…
Defect Calculations for Yttrium Aluminum Perovskite and Garnet Crystals
2000
Native and impurity point defects in both Yttrium Aluminum Perovskite and Garnet crystals are studied in the framework of the pair-potential and the shell model approximations. The calculated formation energies for native defects suggest that the antisite disorder is preferred over the Frenkel and Schottky-like disorder in both YAP and YAG. In non-stoichiometric compounds, the calculated reaction energies indicate that excess of Y2O3 or Al2O3 is, most likely, to be accommodated by the formation of antisites rather than vacancies or interstitials in the lattice. Enthalpies of the reactions for impurity (Ca2+, Mg2+, Sr2+, Ba2+, Cr3+, Fe3+, Nd3+, Si4+) incorporation into both YAP and YAG latti…
<title>Quantum chemical simulation of silicon nanostructures</title>
1999
The point defects in silicon, their migration, geometry and electronic structure, as well as some models for nanowires, were studied. The ab initio Self Consistent Field Molecular Orbital method and the molecular cluster model were used. Hydrogen pseudoatoms were used to saturate dangling bonds of the cluster. The influence of the compression onto defect structure and properties was simulated by changing the bond length value. The silicon interstitial migration activation energy, calculated as the difference between the total energies of the cluster with interstitial in tetrahedral and hexagonal positions, is 4.21 eV, and it does not depend on local pressure. The influence of high pressure …
Evaluation of the Performance of Published Point Defect Parameter Sets in Cone and Body Phase of a 300 mm Czochralski Silicon Crystal
2021
Prediction and adjustment of point defect (vacancies and self-interstitials) distribution in silicon crystals is of utmost importance for microelectronic applications. The simulation of growth processes is widely applied for process development and quite a few different sets of point defect parameters have been proposed. In this paper the transient temperature, thermal stress and point defect distributions are simulated for 300 mm Czochralski growth of the whole crystal including cone and cylindrical growth phases. Simulations with 12 different published point defect parameter sets are compared to the experimentally measured interstitial–vacancy boundary. The results are evaluated for stand…
Delocalized Nature of theEδ′Center in Amorphous Silicon Dioxide
2005
We report an experimental study by electron paramagnetic resonance (EPR) of E(')(delta) point defect induced by gamma-ray irradiation in amorphous SiO2. We obtained an estimation of the intensity of the 10 mT doublet characterizing the EPR spectrum of such a defect arising from hyperfine interaction of the unpaired electron with a 29Si (I=1/2) nucleus. Moreover, determining the intensity ratio between this hyperfine doublet and the main resonance line of E(')(delta) center, we pointed out that the unpaired electron wave function of this center is actually delocalized over four nearly equivalent silicon atoms.
Residual crystalline silicon phase in silicon-rich-oxide films subjected to high temperature annealing
2002
Structural properties of silicon rich oxide films (SRO) have been investigated by means of micro-Raman spectroscopy and transmission electron microscopy (TEM). The layers were deposited by plasma enhanced chemical vapor deposition using different SiH4/O2 gas mixtures. The Raman spectra of the as-deposited SRO films are dominated by a broad band in the region 400-500 cm-1 typical of a highly disordered silicon network. After annealing at temperatures above 1000°C in N2, the formation of silicon nanocrystals is observed both in the Raman spectra and in the TEM images. However, most of the precipitated silicon does not crystallize and assumes an amorphous microstructure. © 2002 The Electrochem…
Luminescence of silicon Dioxide — silica glass, α-quartz and stishovite
2011
Abstract This paper compares the luminescence of different modifications of silicon dioxide — silica glass, α-quartz crystal and dense octahedron structured stishovite crystal. Under x-ray irradiation of pure silica glass and pure α-quartz crystal, only the luminescence of self-trapped exciton (STE) is detected, excitable only in the range of intrinsic absorption. No STE luminescence was detected in stishovite since, even though its luminescence is excitable below the optical gap, it could not be ascribed to a self-trapped exciton. Under ArF laser excitation of pure α-quartz crystal, luminescence of a self-trapped exciton was detected under two-photon excitation. In silica glass and stishov…
Frenkel defect process in amorphous silica
2011
Point defects strongly influence optical properties of synthetic amorphous silica (synthetic a-SiO2) used in excimer laser photolithography and their properties are intensively studied. Decomposition of an Si-O-Si bond into a pair of oxygen vacancy and interstitial oxygen species is an intrinsic defect process in a-SiO2. It is similar to the creation of vacancy-interstitial pairs in crystalline materials and is regarded as "Frenkel defect process" in an amorphous material. Oxygens are also known to be emitted from a-SiO2 surfaces under irradiation with vacuumultraviolet (VUV) light or electron beam. However, the anion part of the Frenkel pair in a-SiO2, interstitial oxygen atom, lacks relia…
Electronic Properties of Point Defects in Metals
1982
Recent progress in electronic structure and related properties of point defects in metals is reviewed. Topics discussed include transition metal impurities in a non-magnetic host, construction of potential energy surfaces from effective-medium theories, trapping of light interstitials, and pair potential in metals.
A microscopic model for long-term laser damage in calcium fluoride
2009
Single crystal calcium fluoride (CaF 2 ) is an important lens material in deep-ultraviolet optics, where it is exposed to high radiation densities. The known rapid damage process in CaF 2 upon ArF laser irradiation cannot account for irreversible damage after long irradiation times. We use density functional methods to calculate the properties of laser-induced point defects and to investigate defect stabilization mechanisms on a microscopic level. The mobility of the point defects plays a major role in the defect stabilization mechanisms. Besides stabilization by impurities, we find that the agglomeration of F-centers plays a significant role in long-term laser damage of CaF 2 . We present …