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Secondary electron (SE) yield, δ , is a very sensitive surface property. The values of δ often are not consistent for even identical materials. The influence of surface changes on the SE yield was investigated experimentally in this article. Argon ion sputtering was used to remove the contamination from the surface. Surface composition was monitored by X-ray photoelectron spectroscopy (XPS) and surface topography was scanned by scanning electron microscope (SEM) and atomic force microscope (AFM) before and after every sputtering. It was found that argon sputtering can remove contamination and roughen the surface. An “equivalent work function” is presented in this thesis to establish the relationship between SE yield and surface properties. Argon ion sputtering of 1.5keV leads to a significant increase of so called “work function” (from 3.7 eV to 6.0 eV), and a decrease of SE yield (from 2.01 to 1.54). These results provided a new insight into the influence of surface changes on the SE emission. [ABSTRACT FROM AUTHOR]

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 (E 1) 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. • Secondary electron yield of gold plating increases non-monotonically with exposure time. • Secondary electron yield of silver plating decreases non-monotonically with exposure time. • Variation of secondary electron emission characteristics greatly affects the multipactor voltage. [ABSTRACT FROM AUTHOR]

• The influence of adsorption of N 2 , O 2 , Ar and air for Ar ion sputtered Cu on the secondary electron emission were researched experimentally. • Different effects of heat treatment on between Ar ion sputtered sample and gas adsorption sample were confirmed. • The relative contents of C and O with different treatment were analyzed by in-situ XPS. • The relationship between the secondary electron yield and secondary electron spectrum was theoretical derivation and experimental validated. Secondary electron (SE) emission is a superficial physical phenomenon. The range of SEs excited in materials which are finally emitted from the surface is generally within a few tens of nanometers. SE emission from materials by electron irradiation has great dependence on surface quality, such as gas adsorption, oxidation, contamination, and morphology. In this paper, the influence of surface adsorption of N 2 , O 2 , Ar and air on SE yield (SEY) and the SE spectrum (SES) of copper was investigated by experiment. The measured SEY and SES were compared before and after the copper surface was sputtered by Ar ions. The results show that gas adsorption could increase SEY, and air adsorption lead to the maximum increase, Ar adsorption the minimum. Meanwhile, the relationship between the SES and the SEY was deduced and validated by the experiment. It was also found in the experiment that the Ar ion sputtering or heating alone can effectively reduce the SEY, while heating the sample after Ar ion sputtering increases SEY. The reasons for the variation of the SEYs with gas adsorption, sputtering and heating are preliminarily explained with the help of in-situ XPS. Accordingly, the research helps to further reveal the mechanism of SEE influenced by complex superficial factors. [ABSTRACT FROM AUTHOR]

• Secondary electron yield of inert metals increases with exposure time. • Surface adsorption layer consisting of carbon and oxygen elements results in the increase. • A two-layers secondary electron yield model is established and parameters of adsorption layer are obtained. • The increase of secondary electron yield can significantly reduce the multipactor threshold. The secondary electron emission (SEE) property of materials is closely related to the multipactor, which is one of the potential risk factors affecting the reliability of high power microwave components for space application. In the presented work, the influence of atmospheric exposure on the secondary electron yield (SEY) of the inert metal is investigated. It is found that the SEY increases gradually with exposing time, and the increase in SEY results from the surface adsorption layer consisting of carbon and oxygen elements. A two-layers SEY model is established to explain this evolution and obtain the corresponding parameters of the adsorption layer. Simulation on a C band impedance transformer shows that 45 days of exposure will result in a 7.5 dB decrease of multipactor threshold. [ABSTRACT FROM AUTHOR]