Electroplating Deposition of Bismuth Absorbers for X-ray Superconducting Transition Edge Sensors |
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| Authors: | Jian Chen Jinjin Li Xiaolong Xu Zhenyu Wang Siming Guo Zheng Jiang Huifang Gao Qing Zhong Yuan Zhong Jiusun Zeng Xueshen Wang |
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| Affiliation: | 1.National Institute of Metrology (NIM), Beijing 100029, China; (J.C.); (X.X.); (S.G.); (Z.J.); (H.G.); (Q.Z.); (Y.Z.);2.College of Metrology and Measurement Engineering, China Jiliang University, Hangzhou 310018, China; (Z.W.); (J.Z.) |
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| Abstract: | An absorber with a high absorbing efficiency is crucial for X-ray transition edge sensors (TESs) to realize high quantum efficiency and the best energy resolution. Semimetal Bismuth (Bi) has shown greater superiority than gold (Au) as the absorber due to the low specific heat capacity, which is two orders of magnitude smaller. The electroplating process of Bi films is investigated. The Bi grains show a polycrystalline rhombohedral structure, and the X-ray diffraction (XRD) patterns show a typical crystal orientation of (012). The average grain size becomes larger as the electroplating current density and the thickness increase, and the orientation of Bi grains changes as the temperature increases. The residual resistance ratio (RRR) (R300 K/R4.2 K) is 1.37 for the Bi film (862 nm) deposited with 9 mA/cm2 at 40 °C for 2 min. The absorptivity of the 5 μm thick Bi films is 40.3% and 30.7% for 10 keV and 15.6 keV X-ray radiation respectively, which shows that Bi films are a good candidate as the absorber of X-ray TESs. |
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| Keywords: | transition edge sensors bismuth absorbers electroplating deposition |
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