Positron lifetime and Doppler broadening spectroscopy were used to investigate porous films which had been heat-treated in an Ar atmosphere. Heating at temperatures between 300 and 500C increased the mass of the film by 17%, due to O uptake, and the concentration of open-volume defects which was associated with the formation of an oxide layer on the nanocrystallites increased by a factor of 3. At temperatures of between 600 and 1000C, their concentration decreased gradually to 50% of the original concentration. The Doppler broadening results indicated the existence of 2 distinct electron momentum distributions. One of these arose from open-volume defects, and the other from the pick-off annihilation of positronium at pore walls; due to electrons with an unexpectedly narrow momentum distribution.

Positron annihilation investigation of porous silicon heat-treated to 1000C S.Dannefaer, C.Wiebe, D.Kerr: Journal of Applied Physics, 1998, 84[12], 6559-64