- 學位論文
X光吸收光譜研究Li:WO3電致色變之電子結構及原子結構
Correlation Between the Electrochromic Properties and the Electronic/Atomic Structures of Li:WO3 Studied by X-ray Absorption Spectroscopy
摘要
本論文主要以臨場X光吸收光譜實驗研究三種不同製程(退火溫度與前置溶液)的氧化鎢薄膜的耐久性以及在重複的染色和退色過程的原子和電子結構。染色過程運用外加正電流使鋰離子鑲嵌進氧化鎢薄膜，薄膜呈現藍色，當外加電流逆電流時薄膜回到原本透明狀態。實驗包含W L3-edge X光吸收近邊緣結構(X-ray absorption near edge structure，XANES)以及W L3-edge延伸X光吸收精細結構 (Extended X-ray absorption fine structure ， EXAFS)。實驗顯示在反覆的染色過程中氧化鎢薄膜的鎢氧八面體變形使結構有序程度下降，在電子結構上奈米晶粒氧化鎢薄膜在第一個染色週期有近 97% 的回復性，與樣品在可見光區的穿透率變化一致，優越的電致色變特性可能是由於在局域上微觀的結構有較優越的鋰離子擴散性和電子的傳導性。
並列摘要
In-situ x-ray absorption spectroscopy of three different types of tungsten oxide thin films were performed to study the electronic structure of the films with repetitive cycles of coloration and bleaching process. In-situ W L3-edge x-ray absorption near edge spectroscopy (XANES) of crystalline and nanocrystalline tungsten oxide films showed that with the coloration the intensity of the spectra decreases and it increases with bleaching, which corresponds to the filling and unfilling of the density of the conduction band, respectively. After repeated cycles of coloration and bleaching the structural disordering was observed from the second derivative of W L3-edge XANES spectra. In-situ extended x-ray absorption fine structure spectra reveal that the atomic structure of the samples remain unaltered after coloration and bleaching. The nanocrystalline tungsten oxide film showed recovery of (~ 97 %) electronic and atomic structure after the first cycle of coloration and bleaching, which was substantially higher compared to other two crystalline samples. It reveals that nanocrystalline sample has superior electrochromic properties than crystalline samples.