Influence of isotopic composition of silicon on local vibrational modes of vacancy-oxygen complex

Isotopic composition of natural silicon (28Si (92.23 %), 29Si (4.68 %) and 30Si (3.09 %)) affects noticeably the shape of infrared absorption bands related to the oxygen impurity atoms. The positions of local vibrational modes (LVMs), related to quasimolecules 28Si – 16OS – 29Si and 28Si – 16OS – 30Si (OS – substitutional oxygen atom) have been determined for the absorption spectra measured at Т ≅ 20 K and at room temperature (Т ≅ 300 K). An estimation of the isotopic shifts of corresponding modes in a semi empirical way has been done by the fitting the shape of the experimentally measured absorption band related to the vacancy-oxygen center in irradiated Si crystals. The LVM isotope shifts at Т ≅ 300 K are found to be (2.22 ± 0.25) сm–1 for 28Si – 16OS – 29Si and (4.19 ± 0.80) сm–1 for 28Si – 16OS – 30Si in relation to the most intense band with its maximum at (830.29 ± 0.09) cm–1 due to the vibrations of 28Si – 16OS – 28Si, and the full width at half maximum of the A-center absorption bands is (5.30 ± 0.26) cm–1. At Т ≅ 20 K the corresponding values have been determined as (1.51 ± 0.13); (2.92 ± 0.20); (835.78 ± 0.01) and (2.34 ± 0.03) сm–1. A model for the calculation of isotopic shifts in the considered case has been discussed. From an analysis of the observed isotopic shifts some information about the structure of the vacancy-oxygen complex in silicon at Т ≅ 20 K and at room temperature has been obtained.

Photoluminescence of LiF Crystals Doped with Oxygen-Containing Impurities

The aim of this paper is to study the photoluminescence spectra and photoluminescence excitation spectra in LiF-O, LiF-WO3and LiF-TiO2crystals at 20-300 K. It is shown that the luminescence centers in LiF-WO3and LiF-TiO2crystals are oxygen ions O2-disturbed by defects. Two absorption bands within 6-4.5 eV and two luminescence bands with maxima at 3.1 eV and 2.64 eV correspond to these centers. The absorption and emission spectra of the oxygen center (3.1 eV luminescence band) are close to those for the (O2-- Va) center.

Hydrogen-Vacancy Complexes and their Deep States in n-Type Silicon

The evolution of irradiation-induced and hydrogen-related defects in n-type silicon in the temperature range 0 – 300 °C has been studied by deep level transient spectroscopy (DLTS) and minority carrier transient spectroscopy (MCTS). Implantation of a box-like profile of hydrogen was performed into the depletion region of a Schottky diode to undertake the DLTS and MCTS measurements. Proportionality between the formation of two hydrogen-related deep states and a decrease of the vacancy-oxygen center concentration was found together with the appearance of new hydrogen-related energy levels.

Structure, Electronic Properties and Annealing Behavior of Di-Interstitial-Oxygen Center in Silicon

It is argued in this work that a DLTS signal associated with hole emission from a radiation-induced defect with an energy level at Ev + 0.09 eV is related to a complex of silicon di-interstitial with an oxygen atom (I2O). This signal has been observed in the DLTS spectra of p-type Si:O samples irradiated with either 4-6 MeV electrons or alpha particles. Isochronal and isothermal annealing studies of the samples have shown that the defect responsible for the DLTS signal from the Ev + 0.09 eV level disappears upon heat-treatments in the temperature range 75-100 °C and its formation and annealing behavior is similar to that of a center giving rise to the infrared absorption band at 936 cm-1 previously assigned to a local vibrational mode (LVM) due to the I2O complex. Possible configurations of the I2O complex have been found by ab-initio modeling and analyzed. Formation and binding energies, energy levels and LVMs for different configurations have been determined. It has been found that the minimum energy configuration of the I2O complex consists of the compact I2 to which a divalent interstitial oxygen atom is attached. Calculated values of the strongest LVM (ν = 971 см-1 ) and position of the donor level {Ev + (0.11-0.13) eV} for the minimum energy configuration are very close to those assigned to the I2O defect in the infrared absorption and DLTS experiments.

Interactions of Self-Interstitials with Interstitial Carbon-Interstitial Oxygen Center in Irradiated Silicon: An Infrared Absorption Study

The evolution of radiation-induced carbon-oxygen related defects with the fluence of MeV electrons and upon subsequent isochronal annealing (75-350 °C) in Si crystals with different carbon and oxygen content has been studied by means of Local Vibrational Mode (LVM) spectroscopy. In particular, the generation kinetics of the bands at 998 and 991 cm-1 is considered and additional arguments supporting their previous assignment to the I2CiOi and I3CiOi complexes are found. An annealing behaviour of the LVMs related to the C4 (ICiOi) defect has been studied in the various Si crystals irradiated with different particles. In all the samples studied the bands at 940 and 1024 cm-1 are found to disappear at about 200 °C while three new LVM bands, at 724 cm-1 (O-related) and at 952 and 973 cm-1 (both C-related) are emerging. Further increase in annealing temperature up to 250-275 °C results in a transformation of the latter bands into another set of LVM bands at 969 cm-1 (O-related) and at 951 and 977 cm-1 (both C-related). These bands disappear upon annealing in the temperature range 300-325 °C. The ratios of all the bands intensities as well as their transformation rates do not depend on the oxygen and carbon content in the Si samples nor on the kind of irradiation (2.5 and 10 MeV electrons, fast neutrons) and irradiation doses. These facts confirm our previous conclusion that all the above-mentioned LVMs arise from the C4 defect being in different configurations (ICiOi, ICiOi*, and ICiOi**).