Abstract
In this work, the surface of Al sheet was coated with a fluorocarbon (FC) thin film by radio frequency (RF) sputtering of polytetrafluoroethylene (PTFE) to investigate the influence of dielectric coatings on the secondary electron yield (SEY) behavior of Al sheets. Atomic-force microscopy (AFM) and energy-dispersive spectroscopy (EDS) were employed to identify the surface topographies and elemental contents of the samples with FC coatings. Water contact angle (WCA) measurements were performed to characterize the surface tension as well as the polar and dispersion components of the samples’ surface. The secondary electron- mission (SEE) behavior of the samples was determined by measuring the SEY coefficients in an ultra-high vacuum chamber with three electron guns. The experimental results indicated that the longer sputtering time effectively led to the increase in coating thickness and a higher ratio of F/C, as well as the continued decrease of surface tension. A quite thin FC coating of about 11.3 nm on Al sheet resulted in the value of maximum SEY (δmax) dropping from 3.02 to 1.85. The further increase in coating thickness beneficially decreased δmax down to 1.60, however, at the cost of a ten-fold thicker coating (ca. 113 nm). It is found that increasing the coating thickness contributes to reducing SEY coefficients as well as suppressing SEE. The results are expected to guide the design of dielectric-coating for SEY reduction as well as multipactor suppression on Al.
Highlights
Secondary electron emission (SEE) is a phenomenon where primary incident electrons hitting a solid or passing through the surface layer of a solid, induce the emission of secondary electrons
It is seen that the1 increased thickness of FC characteristics coatings leads of to FC
11.3 nm coating that resulted the increased of FC coatings leads to the increasing of increase
Summary
Secondary electron emission (SEE) is a phenomenon where primary incident electrons hitting a solid or passing through the surface layer of a solid, induce the emission of secondary electrons. It is a well-known phenomenon of electron-solid interactions that has been regarded as accounting for the multipactor effect in space-based systems. Secondary electron yield (SEY) is frequently used as the index for describing SEE behavior and is defined as the proportion of secondary electron numbers to primary electron numbers. It is known that reducing SEY helps to suppress SEE
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