Evolution of secondary electron emission characteristics of gold plating and silver plating in atmosphere and its effect on multipactor susceptibility chart

The secondary electron emission (SEE) characteristics of materials is one of the issues of interest for microwave components used in space, as it has a decisive effect on the multipactor. In the presented work, the SEE characteristics of gold and silver plating widely used in microwave components is systematically investigated as a function of atmospheric exposure time for up to 400 days. The secondary electron yield (SEY) and the first energy crossover point (E1) increase and decrease non-monotonically with exposure time for gold plating, whereas they decrease and increase non-monotonically for silver plating, respectively. The results of surface characteristics test and analysis indicate that after exposure to the atmosphere, the surface of gold plating has an adsorption layer consisting of C and O elements, which leads to an increase in SEY, while the surface of silver plating becomes rough and a microporous structure is formed on it due to natural chemical reaction, which results in a decrease in SEY. In addition, the analysis results of parallel plate model show that the multipactor voltage is reduced by up to 3 dB for gold plating and increased by up to 3 dB for silver plating after prolonged exposure to the atmosphere.