On the kinetics of sapphire charging and luminescence under electron irradiation

Abstract

The paper presents experimental data on the kinetics of charging and cathodoluminescence (CL) of single-crystal sapphire under electron irradiation. We give a new explanation for the previously found effect of the delay in surface potential development during charging of single-crystal sapphire by an electron beam, and simultaneous increasing of CL intensity. Such a delay can be explained by a gradual accumulation of negative charge in the sapphire volume, which volume is larger than the initial electron-solid interaction region, together with high secondary electron emission. Such charge spreading leads to an increase in the CL intensity throughout the surface potential delay. A hypothesis is suggested that the delay time is determined by the initial number of electron traps. Subsequently, when sufficient charge is accumulated, a retarding electric field arises inside the sample, leading to a decrease of the region of negative charge localization and almost complete neutralization of the positive charge.

Keywords

• Charging kinetics
• Surface potential
• Sapphire
• Cathodoluminescence
• Electron emission
• Point defects