以貼靶濺鍍法製備含GaN量子點之Si3N4及SiOxNy奈米複合薄膜之光學性質研究

Abstract

本論文研究以貼靶鍍法（Target-attached Sputtering Method）製備含氮化鎵量子點（GaN Quantum Dots，GaN QDs）之氮化矽（Si3N4）與矽氧氮化物（SiOxNy）奈米複合薄膜（Nanocomposite Thin Films）。電子顯微鏡（Transmission Electron Microscopy，TEM）分析顯示，兩系統中皆能有GaN QDs的生成，並且分佈密度隨貼靶數增加而增大，但粒徑尺寸則大約維持不變。化學電子能譜儀（Electron Spectroscopy for Chemical Analysis，ESCA）及光激發光譜儀（Photoluminescence，PL）分析得知，SiO2基材會因N2的通入而形成SiOxNy化學組成，並在GaN QDs表面形成了不同於Si3N4中的鍵結組態，使得GaN QDs在SiOxNy中具有較強的表面極化（Surface Polarization）作用，抑制了GaN QDs之VGa缺陷所造成的黃/綠光能階轉移之發光。實驗亦發現當兩系統中的GaN QDs與基材體積比約1：1時會有臨界效應的存在，造成近能帶邊緣（Near-band-edge）能階訊號消失，並有增強缺陷發光的特殊光轉換機制產生。雖然現有數據資料仍無法對此特殊光學轉換機制有完全地了解，但以上分析結果仍足以證明介電質種類對奈米複合薄膜之發光特性有極大的影響。

This work prepares the nanocomposite thin films containing GaN quantum dots (QDs) in Si3N4 and SiOxNy dielectric matrices by using the target-attached sputtering method. Transmission electron microscopy （TEM） revealed the presence of GaN QDs in the both types of thin-film systems. Although the dot density increases with the number of the target-attached pellets, the dot size is independent of that. Electron spectroscopy for chemical analysis（ESCA）and photoluminescence（PL） analyses indicated that the SiO2 matrix may react with N2 injected during sputtering and generate the SiOxNy. It generates a distinct bonding configuration on GaN QDs surface and induces a stronger surface polarization in GaN QDs-SiOxNy system in comparison with the GaN QDs-Si3N4 system. This, in turn, suppresses the yellow-green transition relating to VGa on GaN QDs. Meanwhile, a specific optical transitions, which improves the defect luminescent intensity due to the diminishing of near-band-edge signals, when the volume ratio of GaN QDs to matrix is about 1:1 in both systems. Although present data are insufficient to correlate the optical transition in complete manner, the results above indeed illustrate that the dielectric matrix type has an important effect on the optical properties of nanocomposite thin films.