Gas Desorption and Secondary Electron Emission from Graphene Coated Copper Due to E-Beam Stimulation

Abstract

The gas desorption and secondary electron multiplication induced by electron bombardment tend to induce severe low-pressure discharge effects in space microwave device cavities. Nevertheless, few studies have focused on both secondary electron emission and electron-stimulated gas desorption (ESD). Although the suppression of secondary electrons by graphene was found to be better in our previous study, it is still unclear whether the surface modification of graphene, which brings about different interfacial states, can also be manifested in terms of ESD. The deep mechanism of gas desorption and secondary electron emission from this extremely thin two-dimensional material under electron bombardment still needs further investigation. Therefore, this paper investigates the mechanism of graphene modification on Cu metal surface on the gas release and secondary electron emission properties under electron bombardment. The surface states of graphene-modified Cu were characterized, and the ESD yield and secondary electron yield of Cu/GoCu were investigated using a self-researched platform and analyzed using molecular dynamics simulations and electron Monte Carlo simulations. The results of the study showed that the most released component on the Cu surface under the bombardment of electrons was H2O molecules, while the most released component on the GoCu surface was H2 molecules. The graphene-modified samples showed a significant suppression effect on the secondary electron yield and ESD only in the low-energy region below 400 eV. This study can provide a valuable reference for suppressing low-pressure discharge and multipactor phenomena in space microwave components.

Recent advances in multipactor physics and mitigation

“…The dots represent the experimentally measured multipactor susceptibility boundaries. It is noteworthy that multipactor susceptibility region shrinks with increasing porosity (ρ) and with ρ ¼ 0:66, the model predicts total suppression of the multipactor which agrees with the experimental measurements; therefore, the susceptibility region for ρ ¼ 0:66 is absent in the figure . reported with graphene coated copper [126][127][128]. In 2017, Wu et al proposed a simple fabrication process of porous Ag/ TiO 2 /Au coating [129] to combine a roughened structure with a low SEY material coated surface and obtained a greater SEY reduction with the combined approach than any of the techniques could obtain separately.…”

“…In the Fermilab main injector, diamond‐like Carbon coating (DLC) has been found to mitigate multipactor to roughly 2% of that measured in the uncoated stainless steel beampipe [124]. In addition, significant SEY suppression (of almost up to 50% in [125]) has been reported with graphene coated copper [126–128]. In 2017, Wu et al.…”

“…(b) Comparison of the SEY of stainless steel and a–c coatings [123]; C‐Ne1 represents coating of a–c as received and C‐Ne2 represents coating of a–c aged in air for 2 weeks. (c) Secondary electron yield of Cu (black square dashed curve) and Graphene on Cu (red circle dashed curve) [128].…”

“…(b) Comparison of the SEY of stainless steel and a-c coatings[123]; C-Ne1 represents coating of a-c as received and C-Ne2 represents coating of a-c aged in air for 2 weeks. (c) Secondary electron yield of Cu (black square dashed curve) and Graphene on Cu (red circle dashed curve)[128].F I G U R E 1 1 (a)Instantaneous rf electric field, E y (solid blue line) and normal electric field, E x (broken black line), and secondary electron yield δ (dotted red line) for two-frequency rf field,E y ¼ E rf sinðωt þ θÞ þ βE rf sinðnðωt þ θÞ þ γÞ,[60] with frequency ratio n ¼ 2, initial relative phase of the second carrier frequency, γ ¼ π=2, and relative strength of the second carrier frequency β ¼ 1, at the saturation state for rf carrier amplitude, E rf ¼ 3=ffi ffi ffi MV=m, and frequency of the fundamental carrier mode, f rf ¼ 1 GHz. (b)The corresponding plot of trajectories of the electric field [E x ðtÞ; E y ðtÞ] [60].…”

Physical mechanism of secondary-electron emission in Si wafers

“…Most researchers have concentrated on surface treatment techniques, [15][16][17][18][19] such as the formation of grooved, [20][21][22] fibrous [23,24] and micro-porous [25] structures. However, the SEY increases after surface treatment of the sinusoidal rippled surface [26] and the larger triangular grooves.…”