Hydrogen retention and release dynamics in tungsten oxide layers with various structure and elemental composition

用Kt磁控溅射法和ArF-PLD法在SiO_2、U或ST衬底上沉积了氧化钨薄膜。沉积过程中的衬底温度在300~800K的范围内变化。将Ar和氧气的混合物引入沉淀室，并由质量流量控制器进行调节。沉积的薄膜厚度约为500 nm。用X射线衍射仪和透射电子显微镜对薄膜的晶体结构和微观结构进行了分析。用卢瑟福背散射光谱(RBS)测定了薄膜中W和O的组成。用弹性反冲检测分析(ERDA)技术测量了氢的浓度深度分布。在散射室中利用配备了CCD摄像机的单色仪同时测量了薄膜在200-900 nm波长范围内的光吸收。在室温下，在没有氧气的情况下，两种沉积方法都形成了多晶的β-钨(A-15型结构)。随着氧气的增加，β-钨的长程有序性开始丧失。然后在足够的氧气压力下出现了W03的非晶相。ERD测量表明，氢原子在W03薄膜中分布均匀，其浓度高达H/W=0.7。氢气暴露过程中氢的掺入支持气致变色过程的双注入模型，在该模型中溶解的质子。起到了减少水分的作用。在高真空的热处理过程中，HxWO_3薄膜在600K左右完成了氢的热释放，并伴随着薄膜的变色，表明W6被还原，H20从表面释放出来。氢气在空气中的热释放行为与在真空中的热释放行为相同，但薄膜的变色受到了抑制。

Tungsten oxide thin films were deposited on a SiO_2, U or St Substrates by Kt magnetron sputtering wan a pure metal W target, and by ArF - PLD using a W03 target. The substrate temperature during the deposition was varied in a range between 300 and 800 K. A mixture of argon and oxygen gases was introduced into a deposition chamber and adjusted by a mass-flow controller. The thickness of the deposited films was about 500 run. The crystal structure and microstructure of films were examined by X-ray diffractometry and by transmission electron microscopy. The composition of W and 0 in the film was determined by Rutherford Backscattering Spectroscopy (RBS). The concentration depth profiles of hydrogen were measured by the Elastic Recoil Detection Analysis (ERDA) technique. The optical absorption of the film in wavelength between 200 and 900 urn was simultaneously measured in a scattering chamber using a monochrometer equipped with CCD camera.At room temperature, poly-crystals of beta-tungsten (A-15 type structure) were formed without supplying the oxygen gas for both deposition methods. With increasing the oxygen, the long range order of the beta-tungsten was initially lost. Then an amorphous phase of W03 appeared under sufficient oxygen pressure. The ERD measurements revealed that the hydrogen atoms were uniformly distributed in the W03 film with a concentration as high as H/W = 0.7. The incorporation of hydrogen during the H2 gas exposure supports the double injection model of the gasochromic process, in which the dissolved protons. play a role for reducing Wt. During the heat treatment in a high vacuum, thermal release of hydrogen from the HxWO_3 film was completed at about 600 K, accompanied by the coloration of the film, indicating the reduction of W6 and release of H20 from the surface. The thermal release behavior of hydrogen in air atmosphere was the same as that in the vacuum, whereas the coloration of the film was suppressed.