Infrared activity of hydrogen molecules trapped in Si

The rovibrational-translational states of a hydrogen molecule moving in a cage site in Si, when subjected to an electrical field arising from its surroundings, are investigated. The wave functions are expressed in terms of basis functions consisting of the eigenfunctions of the molecule confined to move in the cavity and rovibrational states of the free molecule. The energy levels, intensities of infrared and Raman transitions, effects of uniaxial stress, and a neighboring oxygen defect are found and compared with existing experimental data

Tunable local polariton modes in semiconductors

We study the local states within the polariton bandgap that arise due to deep defect centers with strong electron-phonon coupling. Electron transitions involving deep levels may result in alteration of local elastic constants. In this case, substantial reversible transformations of the impurity polariton density of states occur, which include the appearance/disappearance of the polariton impurity band, its shift and/or the modification of its shape. These changes can be induced by thermo- and photo-excitation of the localized electron states or by trapping of injected charge carriers. We develop a simple model, which is applied to the $O_P$ center in $GaP$. Further possible experimental realizations of the effect are discussed.Comment: 7 pages, 3 figure

Thermal double donor annihilation and oxygen precipitation at around 650°C in Czochralski-grown Si: Local vibrational mode studies

We have used local vibrational mode (LVM) spectroscopy to monitor the formation of oxygen-related thermal double donors (TDDs) at 450°C and their annihilation at 650°C in carbon-lean Czochralski-grown (Cz-) Si crystals. A few samples were treated at 650°C under high hydrostatic pressure. It is found that the annihilation of TDDs at 650°C results not only in a partial recovery of the interstitial oxygen, but also in the appearance of a number of new O-related LVM bands in the range 990-1110 cm-1. The positions of these lines and their shapes are identical to those observed for Cz-Si irradiated with electrons or neutrons and annealed at 600-700°C. Since the lines appear upon annealing out of V O3 and V O4 defects in irradiated samples, they are suggested to arise from V Om (m>4) complexes. In both kinds of samples, pre-annealed and pre-irradiated, the new LVM bands disappear upon prolonged annealing at 650°C while enhanced oxygen precipitation occurs. The V Om defects are suggested to serve as nuclei for oxygen precipitates developing at around 650°C. High hydrostatic pressure is found to enhance further (up to 4-5 times) the oxygen precipitation process at 650°C in the samples pre-annealed at 450°C. © 2005 IOP Publishing Ltd

Divacancy-oxygen and trivacancy-oxygen complexes in silicon: Local vibrational mode studies

Fourier transform infrared absorption spectroscopy was used to study the evolution of multivacancy-oxygen-related defects in the temperature range 200-300 °C in Czochralski-grown Si samples irradiated with MeV electrons or neutrons. A clear correlation between disappearance of the divacancy (V 2) related absorption band at 2767 cm-1 and appearance of two absorption bands positioned at 833.4 and 842.4 cm-1 at 20 K (at 825.7 and 839.1 cm-1 at room temperature) has been found. Both these two emerging bands have previously been assigned to a divacancy-oxygen defect formed via interaction of mobile V2 with interstitial oxygen (O i) atoms. The present study shows, however, that the two bands arise from different defects since the ratio of their intensities depends on the type of irradiation. The 842.4 cm-1 band is much more pronounced in neutron irradiated samples and we argue that it is related to a trivacancy-oxygen defect (V3O) formed via interaction of mobile V3 with Oi atoms or/and interaction of mobile V 2 with VO defects. © (2010) Trans Tech Publications

Trivacancy-oxygen complex in silicon: Local vibrational mode characterization

FTIR study of the evolution of multivacancy-oxygen-related defects in the temperature range 100-350 °C in Czochralski-grown Si samples irradiated with different particles (10 MeV electrons and 5 MeV neutrons) has been carried out. Appearance of two absorption bands positioned at 833.4 and 842.4 cm-1 has been found upon annealing of the divacancy related absorption band at 2767 cm-1. The 833.4 cm-1 band is assigned to a divacancy-oxygen defect. The 842.4 cm-1 band is much more pronounced in neutron irradiated samples and we argue that it is related to a trivacancy-oxygen defect formed via interaction of mobile V3 with Oi atoms. © 2009 Elsevier B.V. All rights reserved

VOn (n>3) defects in irradiated and heat-treated silicon

Local vibrational mode (LVM) spectroscopy has been used to study the evolution of vacancy-oxygen-related defects (VOn) in the temperature range 300-700°C in carbon-lean Cz-Si samples irradiated with MeV electrons or neutrons. New experimental data confirming an attribution of the absorption bands at 910, 976 and 1105 cm-1 to the VO3 complex are obtained. In particular, a correlated generation Of VO3 and the oxygen trimer is observed upon irradiation of CzSi crystals in the temperature range 300-400°C. Strong evidence for the assignment of the bands at 991 and 1014 cm-1 to a VO4 defect is presented. The lines are found to develop very efficiently in the VO2 containing materials enriched with the oxygen dimer. In such materials the formation of VO 4 is enhanced due to occurrence of the reaction O 2i+VO2 ⇒ VO4. Annealing of the VO 3 and VO4 defects at T > 550C °C is found to result in the appearance of new defects giving rise to a number of O-related LVM bands in the range 990-1110 cm-1. These bands are suggested to arise from VO5 and/or VO6 defects. Similar bands also appear upon the annihilation of oxygen-related thermal double donors at 650°C in Cz-Si crystals pre-annealed at 450°C