CsGeI3粉末合成及晶體成長之研究

Abstract

本研究是以熱反應法加上布氏長晶法生長CsGeI3晶體，成功的以熱反應法合成複晶原料，並以無晶种方式成長晶體。在合成複晶原料方面，CsI+GeI2配方以550℃搖混8小時、6小時爐冷為最佳條件；而CsI+Ge+I2配方以700℃搖混8小時、6小時爐冷為最佳條件。經X光繞射儀驗證我們所成長之晶體為R3m空間群鈣鈦礦結構的CsGeI3晶體。我們進一步作了DTA分析，得知290.3℃為R3m與Pmmm空間群之相轉變點、433.47℃為溶點、450.68℃為分解點。 所成長之晶體作了變溫及不同聚焦情況之PL量測，螢光峰值發生位置為728nm、788nm、409nm等波長。室溫之拉曼光譜量測，發現拉曼位移峰值為293cm-1與268cm-1。

CsGeI3 (CGI) poly-crystal was synthesized. We also grown the Cs GeI3 Crystal in vertical Bridgman method without seeding. The X-ray diffraction data showed that our crystal CGI is perovskite sturcture and belogns to R3m space group. We identified that CGI has Phase Transition from space group R3m at 290℃ to Pmmm and the melting point is 433.47℃ by Differential Thermal Analysis (DTA) results. CGI was disslved at 450.68℃ if we kept raising the temperature. In photo-luminescence measurements, there were 728nm, 788nm, 409nm peaks which were measured in different temperature and focused condition. We also found 293ch-1 and 268cm-1 Raman shifts in Raman Spectroscopy detection at room temperature. Those Raman shift should be caused by the stretched and anti-stretched modes of GeI2 cluster.