- 學位論文
光源輔助濕蝕刻對GeSbTe硫屬化合物薄膜之微結構及光學特性研究
Study of the Microstructure and Optical properties for GeSbTe chalcogenides by Photo-assisted Wet Etching
摘要
太陽電池的光照面一般都會有抗反射層結構，來減少入射陽光的反射，其在增加入射光穿透太陽能電池模組的能量，使太陽能電池達到更高的光電轉換效率。至今較少論文或期刊探索Ge2Sb2Te5薄膜材料的蝕刻機制，經由蝕刻後薄膜材料表面形態及表面粗糙度變化，評估其在抗反射層上應用的可能性。本研究使用直流濺鍍法來製備Ge2Sb2Te5化合物薄膜，在硝酸水溶液蝕刻Ge2Sb2Te5薄膜的同時，藉由可見光光源的輔助，並以SEM、AFM、UV-Visible光譜儀等儀器分析表面性質及光學特性，觀察薄膜表面對光源輔助蝕刻後的變化。 實驗中我們發現，可以使Ge2Sb2Te5薄膜產生較佳多孔性結構，最佳蝕刻液的濃度為20 wt%。薄膜厚度、孔洞尺寸、表面粗糙度並不隨著照光強度持續增加而成正比趨勢。縱觀從在相同蝕刻時間下，不同光源輔助蝕刻對薄膜厚度、孔洞尺寸、表面粗糙度的變化。我們可以大膽假設硝酸液對Ge2Sb2Te5薄膜蝕刻模型。依據此模型，我們可以推測薄膜蝕刻行為變化。
並列摘要
The surface of solar cell will generally have an anti-reflective layer structure to reduce the incidence of the reflection. Increasing the incident light penetration in the solar cell modules can achieve higher photoelectric conversion efficiency. Few papers explore the etching mechanisms of Ge2Sb2Te5 thin films and the related optic properties of the films. The surface morphology and surface roughness changes by etching the thin films with and without light source implied the possible application of the films on the anti-reflective layer in devices. In this study, the Ge2Sb2Te5 films are deposited by direct current (DC) sputtering system. The visible light was used to assist etching of Ge2Sb2Te5 films in an aqueous HNO3 solution. The SEM、AFM、UV-Visible spectroscopy were used to analyze of the surface and optical properties of the thin films. The film surface was also observed after photo-assisted etching by the same measurement tools. It was found that Ge2Sb2Te5 film can result in better porous structure by aqueous etching process. The ooptimal concentration of the etching solution was 20 wt%. The film thickness、porous size、roughness does not change with increasing illumination intensity is inversely proportional to the trend continuing.Throughout the same etching time with different photo-assisted etching processes shows that the film thickness, porous size, surface roughness were more changed than the non-photo etching process. We can speculate and propose a model of the film etching behavior of Ge2Sb2Te5 film with nitric acid etching solution.