鐵濺鍍膜於含氟乙二醇溶液中陽極蝕刻的溫度變化對其氧化鐵產物微結構、光學與光電特性之影響

Temperature Effect on the Microstructure, Optical and Photoelectrochemical Characteristics of Fe2O3 Resulted from Fe-sputtered Films through Electrochemical Etching in F-containing Ethylene Glycol Solution

本研究以磁控濺鍍系統（magnetron sputtering system）於F-doped SnO2薄膜基板（FTO）上成長Fe薄膜，並於含氟之乙二醇水溶液中，進行二極式陽極蝕刻；蝕刻後之薄膜於550℃箱型爐中退火2小時，並以三極式電化學系統於強鹼溶液中進行光電化學實驗以檢測其分解水之能力。本文著重於探討陽極蝕刻程序下溫度對於鐵膜蝕刻後表面形貌的變化和它在進行光分解水的效率影響。結果顯示:控制蝕刻液在20 ~ 60℃溫度範圍內，經20 V蝕刻2 min，550℃退火2小時後，試片呈現三種不同表面形貌，分別為薄膜（20℃）、奈米顆粒（40℃）及奈米柱（60℃）；若增長蝕刻時間至3 min則會有過蝕刻現象無法應用於光電化學。蝕刻後之試片550℃退火2小時，由XRD及拉曼分析得知其結構屬於純赤鐵礦（無二次相產生），比較三種蝕刻薄膜之光電化學反應，結果顯示：於60℃陽極蝕刻所得之奈米柱結構的光電流最佳（0.59 mA/cm2）。

Pure iron films were deposited on the fluorine-doped SnO2 (FTO) glass substrate by DC magnetron sputtering process. The nano-films were subjected to anodic etching in the F-containing ethylene glycol solution at temperatures ranging from 20 to 60 ℃. The etched samples were annealed in a 550 ℃-furnace under air ambient for 2 h, then examined their surface morphology through scanning electron microscopy (SEM), and determined their crystal structure with x-ray diffraction (XRD) and Raman spectroscopy. Three-eletrode cell was used to conduct photoelectrochemical (PEC) testing in alkaline solution illuminated with a UV-visible light source for evaluation the photo-catalytic decomposition of water. Resultant from XRD analysis and Raman spectra, all the etched samples after post annealing were pure hematite (α-Fe2O3). Through SEM observation, the etched morphology of the films depended upon the etching temperature. It formed films, nano-particles and nanorods while the etching temperatures were 20, 40 and 60 ℃, respectively. The PEC results revealed that the hematite (α-Fe2O3) with the morphology of nanorods, resultant from anodic etching at 60 ℃, showed the highest photoelectrochemical current density (0.40 mA/cm2) at 0.6 V vs. SCE compared to other specimens.