Analysis of thermal detrapping of holes created by electron irradiation in high purity amorphous SiO2 using the induced and secondary current measurements

摘要

Isothermal detrapping of holes after electron irradiation (using a SEM) in high purity amorphous SiO2 is evaluated at different temperatures (in the range 300-663 K) by means of the induced and secondary current measurements. In order to single out the hole detrapping, the specific charging conditions (1 keV defocused electron beam of low density) leading to positive charging are adopted. The thermal detrapping, which stems from a single trap, begins at 523 K and is completed at 663 K. After annealing in air at 973K during 48h, two detrapping stages are revealed: the former is connected with an additional shallow trap, while the latter requires temperatures above 663 K for a complete detrapping. The first order kinetics describes reasonably well the detrapping process. The frequency factors (near 10(10) s(-1)) and the activation energies (about 1.6 eV) deduced from this analysis could be assigned, respectively, to the relaxation connected to detrapping and to the trap energy level of the charged oxygen vacancy. (C) 2015 Elsevier B.V. All rights reserved.