Preparation of electrochemically active hydrate and hydroxide thin films by sputtering

水合Ta_2O_5是一种质子导电固体电解质，羟基氧化镍（NiOOH）是一种电致变色材料。采用反应溅射法制备了水合Ta_2O_5和NiOOH薄膜。1）以H_2O为反应气体，反应溅射Ta金属靶。在溅射过程中将衬底温度冷却到-20℃以减少H_2O分子从薄膜表面的脱附。利用Ratherford背散射（RBS）和氢前向散射（HFS）对Ta_2O_5薄膜中氢原子的掺入量进行了估算。结果表明，随着衬底温度的降低，Ta_2O_5薄膜中的氢含量增加，在衬底温度为-20℃时，H/Ta原子比达到最大值2.2。通过X射线反射率（XRR）测量发现膜密度随着衬底温度的降低而降低。Ta_2O_5薄膜的离子电导率随氢含量的增加而增加，在基片温度为-20 ℃时达到最大值4 × 105 S/cm。2）采用O_2+H_2O混合气体反应溅射Ni金属靶<-8>，傅立叶变换红外光谱（FTIR）分析表明，当水流量比大于5%时，NiOOH薄膜形成。在KOH水溶液中研究了NiOOH薄膜的电致变色性能，得到了约30 cm ^2/C的着色效率。3）利用水合Ta_2O_5固体电解质和NiOOH电致变色层制备了全固态反射型电致变色器件，得到了5：1的反射率变化。今后，我们将致力于寻找具有高离子电导率的新型固体电解质材料，开发高性能的薄膜电化学器件。

Hydrated Ta_2O_5 is a proton-conducting solid-electrolyte and Ni oxyhydroxide (NiOOH) is an electrochromic (EC) material. Thin films of hydrated Ta_2O_5 and NiOOH were prepared by reactive sputtering, which is one of the most widely used dry processing methods.1) A Ta metal target was reactively sputtered using H_2O as a reactive gas. Substrate temperature was cooled to -20℃ during sputtering to decrease the desorption of H_2O molecules from the films surface. The amount of hydrogen atoms incorporated into the Ta_2O_5 films was estimated by Ratherford Back Scattering (RBS) and Hydrogen Forward Scattering (HFS). It is found that hydrogen content in the Ta_2O_5 films increased with decreasing substrate temperature and a maximum H/Ta atomic ratio of 2.2 was obtained at a substrate temperature of -20℃. The film density was found to decrease with decreasing substrate temperature by X-ray Reflectivity (XRR) measurement. Corresponding to the increase of the hydrogen content and the decrease of film density, the ion-conductivity of the Ta_2O_5 films increased and a maximum ion-conductivity of 4x10^<-8> S/cm was obtained at a substrate temperature of -20℃.2) A Ni metal target was reactively sputtered using O_2+H_2O mixed gas, and the formation of NiOOH thin films was confirmed at H_2O flow ratios above 5% by Fourier Transform Infrared Spectroscopy (FTIR). EC properties of the NiOOH thin films were studied in a KOH aqueous electrolyte and a coloration efficiency of approximately 30 cm^2/C was obtained.3) All-solid-state reflective-type EC devices were fabricated using the hydrated Ta_2O_5 solid-electrolyte and the NiOOH EC layers, and reflectance change of 5:1 was obtained.From these results, it is clarified that hydrate and hydroxide thin films can be prepared by the sputtering method. In the future, we will search for new solid electrolyte materials with high-ion-conductivity and develop high-performance thin-film-electrochemical-devices.