Analysis of the scanning electron microscope mirror method for studying space charge in insulators

Abstract

Articles you may be interested inMeasurement of surface potential of insulating film on a conductive substrate in a scanning electron microscope specimen chamberWe give a detailed analysis of the scanning electron microscope mirror method for studying a cloud of charge stored near the surface of an insulator, paying particular attention to the approximations that are often made. We discuss the effect of the finite size of the experimental chamber, of the thickness of the sample, and of relativistic corrections, and we demonstrate that interpretation of the observations cannot be unique. By making a detailed computation of the electron orbits in the presence of extended sources, we then test the commonly made assumption that the method measures the radius of curvature of the equipotentials, and we show that this is only partially true. Finally, we show that the sensitivity could be improved by increasing the scattering angle.

Alumina based ceramics for high-voltage insulation

“…[8][9][10][11] They give information on the ability of the insulator to carry and trap electric charges. These measurements are performed with a scanning electron microscope equipped with a beam blanking unit which permits an accurate check of the irradiation time, and a conductive cold-hot stage linked to the ground via a picoammeter.…”

An anomalous contrast in scanning electron microscopy of insulators: The pseudo‐mirror effect

“…The built-up electric field in the vacuum resulting from the trapped electrons in the specimen leads to an image distortion and to secondary electrons (SE) contrast dependence on the local sample charging. One of the most spectacular observations related to the negative charging is the well-known mirror effect (Clarke et al 1970, Vallayer et al 1999, Wintle 1999. The mirror image is the result of a two-step process.…”

Space Charge in Irradiated Insulators: Mirror Method

“…The mirror image formation has been described in various articles [2][3][4][5][6][7] and we just summarize here some important points. When the electron beam of the SEM is scanned over the specimen, the usual image of the considered sample gives place to the mirror image, which displayed a distorted view of the chamber (see Fig.…”

“…In earlier paper [2][3][4][5][6][7], authors assert that, in a general way, the use of optical geometrical Ansatz permits us to determine the rnirror plot relation Ild = J(V) and thus to evaluate the corresponding charge distribution. However, there does not appear to be any firm basis for this hypothesis.…”

“…Since the invention of mirror method, considerable work has been accomplished in order to extract information concerning electrical characteristics of insulator [2][3][4][5] as well as the associated trapping and detrapping mechanism. In fact, the effect of "electrostatic mirror", as pointed out by Le Gressus et al [2] into 1991, is largely used in particular to study the trapping charge efficiency in oxides or polymers.…”