An electron-induced secondary electron model for photoelectric sensitivity and quantum efficiency of metal surfaces

Abstract

This paper studies an electron-induced secondary electron model ESEM for photoelectric sensitivity PS and quantum efficiency QE of metal surfaces near threshold frequency γ0, which was developed from Sommerfeld’s theory and the theories of transport and escape of electron-induced secondary electrons. The ESEM includes the effects of γ and T, properties of metals (Fermi energy and work function φ including Schottky effect) and applied field on metal surface, where T is Kelvin temperature, γ is the frequency of incident light. The PS curves show that for γ near γ0 there is a marked increase in photoemission with T, for γ farther away there is no change of photoemission with T, and for γ still father away there is a slight decrease in photoemission with T; these characteristics of PS curves were explained, respectively. Two methods of determining φ by using formulas deduced here for PS or QE curves of metal surfaces near γ0 to fit corresponding experimental data were presented, respectively. The ESEM is compared with existing widely used classical models, i. e., the three-step model and the Fowler-DuBridge model. Even though with different assumptions and settings, it is found that PS and QE curves of metal surfaces near γ0 in ESEM agree well with corresponding curves in other models, and that the ESEM has several advantages over other models.

Keywords

• Photoelectric sensitivity
• Quantum efficiency
• Metals
• Work function
• Secondary electron emission
• Applied field