Consequences of anisotropy in electrical charge storage: application to the characterization by the mirror method of TiO2 rutile

This article is devoted first to anisotropic distributions of stored electric charges in isotropic materials, second to charge trapping and induced electrostatic potential in anisotropic dielectrics. On the one hand, we examine the case of anisotropic trapped charge distributions in linear homogeneous isotropic (LHI) insulators, obtained after an electron irradiation in a scanning electron microscope. This injection leads to the formation of a mirror image

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

International audienceIsothermal 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

Modeling of secondary electron emission and charge trapping in an insulator under an electronic beam

International audienceCharge accumulation in an insulator, as achieved by electron irradiation in a SEM, is governed by complex phenomena. The understanding of the relevant processes (the generation of free carriers, transport and trapping/de-trapping) is a prerequisite for the design of materials having improved breakdown strengths. A simple modeling, which meets the planar geometry conditions, is proposed. The predictions of the evolution of secondary electron emission yield (as function of the quantity of trapped charges) agree well with the experimental results at room temperature, in pure amorphous SiO2. The agreement is obtained with trapping cross-sections near 10-10 cm2, which are much higher than the typical values (about 10-16 cm2). Trapping appears as an “effective” process that reflects the Brownian motion of secondary electrons