脈衝雷射成長銅銦鎵硒薄膜與其物理特性之超快載子動力學研究

Abstract

本論文利用脈衝寬度分別為奈秒(ns)及飛秒(fs)之雷射源來蒸鍍銅銦鎵硒(CIGS)薄膜於不同鈉(Na)濃度摻雜的基板上。以比較不同脈衝寬度的雷射導致的成長機制影響與Na摻雜對於CIGS薄膜的作用，我們藉由X-ray繞射儀(XRD)及拉曼光譜儀(Raman spectroscopy)來探討其結晶特性，以掃描式電子顯微鏡(SEM)比較其結晶形貌。之後，利用積分球來量測CIGS薄膜的光學特性與能隙。最後以光激發螢光光譜(Photoluminescence spectrum)與光激發-探測系統量測其缺陷與超快載子動力學行為。從XRD量測結果發現，fs PLD CIGS薄膜有其多晶性且各軸向之結晶性較佳，經由Na摻雜後更加明顯。而由拉曼及PL光譜顯示ns PLD由於機制的關係較容易剝離靶材的二次相Cu2−xSex。之後，透過SEM可以發現兩者表面形貌有極大的差異性，並觀察到鈉的摻雜可以鈍化晶界(Grain boundary)。而樣品之超快載子動力學亦觀察到，fs PLD薄膜其缺陷相關非輻射復合率較ns PLD低，並觀察到鈉的摻雜也能減少其缺陷複合。

In this thesis, We prepared copper indium gallium selenide (CIGS) thin films at different sodium (Na) doped substrate by pulsed laser deposition(PLD),the pulse widths are nanoseconds (ns) and femtosecond (fs) laser thin films at different sodium (Na) doped substrate. To compare different laser pulse width effects on the growth mechanism for CIGS thin film and doped with Na or not , we used X-ray diffraction (XRD) and raman spectroscopy (Raman spectroscopy) to investigate the crystallization characteristics . Scanning electron microscopy (SEM) to compare the crystal morphology. integrating sphere to measure the optical properties and bandgap of thin film. Finally, photoluminescence (Photoluminescence spectrum) and femtosecond pump-probe spectroscopy measure ultrafast carrier dynamics. From the XRD, fs PLD CIGS thin film has its nature polycrystalline and crystalline is better via Na doped. By the Raman and PL spectra ns PLD easier to peel off target secondary phase Cu2-xSex because the mechanism. After both can be found through SEM surface morphology have great differences, and observed that the doping of sodium can passivate grain boundaries. The sample of ultrafast carrier dynamics are observed, fs PLD films with defect-related non-radiative recombination rate is lower than the ns PLD and observed that the doping of sodium can also reduce defect generated.