Measurement of internal electric field in coated grounded quartz irradiated by an electron beam

Physical mechanisms involved in insulators submitted to electron irradiation inside a scanning electron microscope (SEM) are investigated by combining some simple considerations of electron trapping mechanisms with basic equation of electrostatics. To understand such mechanisms, only widely irradiated samples having a uniform trapping sites distribution are considered. This hypothesis leads to develop simple models for the trapped charge distributions and subsequently for the distribution of the electric field build-up in ground coated specimens as investigated in electron probe microanalysis (EPMA). This enables us to study the distortion of the Φ(ρz) function (the depth distribution of characteristic X-ray production) as well as the modification of the specimen's local composition. In this paper, an experimental method, using a series of quartz samples, is described for evaluating the magnitude of the electric field build-up within specimens; thus allowing to establish clearly the electric field influence on the measured Φ(ρz) function.