Abstract
Porous Ag/TiO2/Au coatings with excellent multipactor suppression were prepared by fabrication of porous Ag surface through two-step wet chemical etching, synthesis of TiO2 coatings by electroless-plating-like solution deposition and deposition of Au coatings via electroless plating. Porous structure of Ag surface, TiO2 coatings on porous Ag surface and Au coatings on porous Ag/TiO2 surface were verified by field-emission scanning electron microscopy, the composition and crystal type of TiO2 coatings was characterized by X-ray photoelectron spectroscopy and X-ray diffraction. Secondary electron yield (SEY) measurement was used to monitor the SEY coefficient of the porous Ag coatings and Ag/TiO2/Au coatings. The as-obtained porous Ag coatings were proved exhibiting low SEY below 1.2, and the process was highly reproducible. In addition, the porous Ag/TiO2/Au coatings showed excellent multipactor suppression with the SEY 1.23 and good environmental stability. It is worth mentioning that the whole preparation process is simple and feasible, which would provide a promising application in RF devices.
Highlights
Multipactor is a potentially detrimental phenomenon in RF devices in space, such as high-energy particle accelerators[1] gyroklystron[2] waveguide filters[3] and so on
Gold coatings with low surface resistance, low Secondary electron yield (SEY), and stable chemical and physical structure, on a rough silver surface are considered as a viable alternative[16], whereas that will probably be formed into gold-silver alloy, which is unbeneficial to RF devices
We presented the comparison of the maximum SEY of the porous surface between the study and the reported literature in Table 3, the maximum SEY of the porous Ag surface is lower than that reported in literature, the SEY suppression and environmental stability of porous Ag/ TiO2/Au surface is more excellent
Summary
Multipactor is a potentially detrimental phenomenon in RF devices in space, such as high-energy particle accelerators[1] gyroklystron[2] waveguide filters[3] and so on. Porous materials that can effectively trap escaping secondary electrons, are prepared to suppress multipactor. Titanium dioxide(TiO2) film was chosen to be synthesized as transition layer prior to the deposition of Au coatings on porous Ag surface for several reasons, including its low cost, electronic properties, and easiness of thin film preparation. Many works have been performed on preparation of TiO2 films, including physical and chemical methods, such as magnetron sputtering method[17], atomic layer deposition[18], sol-gel method[19], electroless-plating-like solution deposition (EPLSD) approach[20,21], etc. We developed an available method to fabricate TiO2 films on porous Ag surface, which is called the EPLSD, but the preparation mechanism is different from that of the above approach. The EPLSD we reported would achieve conformal and dense TiO2 thin films
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