Optical modulation of low-energy-electron reflection and transmission at a Si surface

Abstract

This paper reports the optical modulation of both the transmitted and backscattered currents which result when a primary beam of low-energy electrons is incident on an Ar-bombarded Si (111) surface. It is shown that the dependence of these optically modulated currents on electron energy can be separated into two components. The first component consists of a sharp peak at low incident-electron energies and is correlated with the photovoltaic modulation of the contact-potential difference between the electron gun and Si target. The second component is attributed to the photovoltaic modulation of the escape probability for secondary electrons which are created by the incident primary electrons. A theoretical model based on this physical interpretation correctly predicts the qualitative dependence of optically modulated currents on a number of experimental parameters such as incident-electron current, electron energy, incident light, and sample temperature.