Characteristics of secondary electron emission from metal surface onto gas adsorption

Abstract

The thickness of the adsorption layer typically ranges from a few nanometers to several hundred nanometers, which is comparable to the interaction range of electrons with metals. Therefore, adsorbed gases can significantly influence secondary electron emission characteristics. This study investigates gas adsorption/desorption experiments using Ag samples, with N2, O2, and air as the background gases for adsorption. The effects of gas adsorption on material surface properties were analyzed, and a comparative study was conducted on secondary electron yield, secondary electron energy spectra, desorption amount, and surface x-ray photoelectron spectroscopy composition changes under different conditions—ion cleaning, gas adsorption, and thermal desorption. The results show that the secondary electron yield of a clean surface increases to varying degrees after gas adsorption, depending on the gas type and adsorption quantity. After 12 h of exposure to different gases (N2, O2, and air), the adsorption thickness reached approximately 2–3 nm, and the gas desorption amount after heating was on the order of 1015 molecules/cm2. Additionally, samples treated in an air environment exhibited significant H2 desorption, indicating that water vapor adsorption has a substantial impact on the secondary electron emission characteristics of metal surfaces.