Positron Annihilation Spectroscopic Studies of Sintering Effect on Sol–Gel-Synthesized SiO2 Wide Band Gap Semiconductor Nanocrystals

Sol–gel procedure followed by sintering was used to prepare silica nanoparticles. Their structural properties were examined using XRD and HRTEM. Estimation of band gap and characterization of various type of defects were carried out by UV-Vis spectroscopy and positron annihilation spectroscopy. Though bulk SiO2 is an insulator, calculated band gap was in the range of wide band gap semiconductor region. High value of positron lifetime indicated presence of void type defects on sintering in air. The defect profile has changed from unsintered samples. Coincidence Doppler broadening spectroscopy revealed the momentum characteristics of core as well as valence electrons.