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

摘要

This paper studies an electron-induced secondary electron model ESEM for photoelectric sensitivity PS and quantum efficiency QE of metal surfaces near threshold frequencyγ0, which was developed from Sommerfeld’s theory and the theories of transport and escape of electron-induced secondary electrons. The ESEM includes the effects ofγandT, properties of metals (Fermi energy and work functionΦincluding Schottky effect) and applied field on metal surface, whereTis Kelvin temperature,γis the frequency of incident light. The PS curves show that forγnearγ0there is a marked increase in photoemission withT, forγfarther away there is no change of photoemission withT, and forγstill father away there is a slight decrease in photoemission withT; these characteristics of PS curves were explained, respectively. Two methods of determiningΦby using formulas deduced here for PS or QE curves of metal surfaces nearγ0to 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 nearγ0in ESEM agree well with corresponding curves in other models, and that the ESEM has several advantages over other models.