Doppler broadening of annihilation radiation was studied using float-zone-grown Si crystals, near to the melting point, by means of a positron micro-beam. Below 1380C, the broadening of annihilation radiation spectra exhibited essentially no change. Within a very narrow temperature range, close to the melting point, the peak intensities of the broadening of annihilation radiation spectra (S parameter) decreased by approximately 1%; suggesting an increase in material density. Upon further heating, the S parameter markedly increased up to melting. This indicated the formation of thermal vacancies.

Vacancy Generation in Si During Solid–Liquid Transition Observed by Positron Annihilation Spectroscopy. M.Maekawa, A.Kawasuso: Japanese Journal of Applied Physics, 2009, 48[3], 030203