Extensive experiments studies of the - IV elements have been made in recent years. Motivations have included the rich variety of phase and structural transitions.

Different SiO_2-x defects can be created in Czochralski grown silicon, Cz - Si, by appropriate pre-annealing at atmospheric pressure (10⁵ Pa). Some data concerning the effect of enhanced hydrostatic pressure on creation of defects in the nanomaterial Si - SiO_2-x system have been reported for defects - containing Cz - Si subjected to the cyclic hydrostatic pressure treatment.

The increase of defect concentration in the hydrostatic pressure - treated Cz- Si nanomaterial samples with initially present SiO_2-x precipitates can be considered as a proof of hydrostatic pressure - induced massive creation of defects on before - created oxygen - related defects. However, in the case of some DAC - treated samples, a misfit dislocation network was not directly proved to be created because of too small sample dimension in comparison to the resolution of the spectroscopy and X-ray methods.

The study of these nanomaterial samples was carried out by spectroscopical methods under pressure too. In particular, it was revealed that the sample with high deffect density indicated the transparency ~ 55-70% in the wavelength range 800-1100 nm with some maximum at 930 nm at the initial state the effect possibly connected with the sample non-homogeneity. At application of the high pressure (~5 GPa) the value of transparenvy decreases up to ~10% in the wavelength range of 800-925 nm and later on transparency value increases sharply to ~100% at 1100 nm wavelength. Further pressure rise (up to ~10 GPa) resulted in an increase of the transparency value up to 20% at 800-900 nm range and later on it increases up to 55% at 1100 nm wavelength. Thus with the pressure rise, the absorption edge of forbidden zone moved to higher wavelengths.