電漿增強式化學氣相沈積法成長超晶格結構以製備奈米矽晶及其特性研究

Abstract

本論文中，利用電漿增強式化學氣相沈積法成長超晶格結構薄膜，其中包含兩種不同材料結構，非晶矽/二氧化矽和富矽氧化矽/二氧化矽的超晶格結構，並接著高溫熱退火的製程，成功於超晶格薄膜中成長出奈米矽晶，透過高解析穿透式電子顯微鏡的觀測，在薄膜中發現明顯規則排列的晶格結構，並搭配電子束的晶格繞射圖像，證實薄膜中奈米矽晶的存在，再透過量測靜態和動態光激螢光頻譜，對奈米矽晶的發光特性進行研究。 在超晶格結構中，利用沉積不同厚度的非晶矽層或富矽氧化矽層，能夠有效的控制奈米矽晶的顆粒大小，由光激螢光頻譜的量測可以觀察到，隨著沉積厚度減少，發光強度開始增強，然後接著減弱，並伴隨波長有藍移的現象，此乃因為奈米矽晶尺寸變小，基於量子侷限效應對奈米矽晶能階造成了影響。最後，透過時間解析螢光頻譜的量測，發現在不同奈米矽晶顆粒大小會影響載子生命期。

In this thesis, we have deposited superlattice thin films by Plasma enhanced chemical vapor deposition(PECVD), including two different kind of material: amorphous Si/silicon dioxide(a-Si/SiO2), silicon-rich oxide/silicon dioxide(SRO/SiO2). Followed by thermal annealing, an apparently ordered structure of silicon atomsand its diffraction pattern were observed by transmission electron microscopy (TEM), which verified the existence of Si-nanocrystals inside the superlattice thin film.Thecharacteristics ofSi-nanocrystals were also studiedby continuous-wave photoluminescence(PL) and time-resolved PL. In the superlattice structure, a-Si or SRO sub-layers were deposited in different thickness and different periodsto control the grand size of Si-nanocrystals. From the PL spectra, we can observe the increasingemission intensitywith the decreasing sub-layer thickness of the thin film, and thendecreasing of the intensity is followed. Blue shift is also observed, which means the grain size is decreasedand quantum confinement has affected the energy levels of Si-nanocrystals. The carrier lifetime also is influenced by the same effect, and can be characterized by time-resolved PL measurement.