Vacancy generation in Si during solid-liquid transition observed by positron annihilation spectroscopy

The Doppler broadening of annihilation radiation (DBAR) measurements were performed on Czochralski and floating-zone-grown Si crystals near the melting point using a positron microbeam. Below 1380degC, the DBAR spectra showed essentially no change. In a very narrow temperature range near the melting point, the peak intensities of the DBAR spectra (S parameter) decreased by approximately 1% suggesting an increase in material density. Upon further heating, the S parameter markedly increased until melting. This indicates the formation of thermal vacancies. Compared with theoretical calculation, both monovacancies and divacancies are considered to be formed. (author)