Preparation of electrochemically active hydrate and hydroxide thin films by sputtering

水合Ta_2O_5是质子导电固体电解液，氢氧化镍是电致变色材料。采用反应溅射法制备了水合Ta2O5和NiOOH薄膜。1)以H2O为反应气体，反应溅射Ta金属靶。在溅射过程中，衬底温度降至-20℃，以减少H2O分子在薄膜表面的脱附。用Ratherford背散射(RBS)和氢前向散射(HFS)估算了Ta2O5薄膜中的氢原子量。结果表明，随着衬底温度的降低，Ta2O5薄膜中的氢含量增加，当衬底温度为-20℃时，薄膜的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，薄膜密度随衬底温度的降低而降低。随着薄膜中氢含量的增加和薄膜密度的降低，Ta2O5薄膜的离子电导率增加，在衬底温度为-20℃时，薄膜的最大离子电导率达到4×10~(-8)&gt；S/cm。2)用O2+H2O混合气体反应溅射Ni金属靶，用傅立叶变换红外光谱证实了当H2O流量比大于5%时，NiOOH薄膜的形成。3)利用水合Ta2O5固体电解质和NiOOH电致发光薄膜制备了全固态反射型电致发光器件，获得了5：1的反射率变化，说明采用溅射方法可以制备水合物和氢氧化物薄膜。在未来，我们将寻找具有高离子导电性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.