利用掃描式近場光學顯微術研究微米與奈米尺度半導體結構樣品

Abstract

在本論文中，我們利用高解析度掃描式近場光學顯微術研究微碟、光子晶體共振腔與半導體量子點在次微米尺度下的光學特性，並與模擬的結果相比較。利用微碟的近場影像，可以觀察到耳語廊模態在微碟圓周區域形成，其模態橢圓狀光場數目約為模擬個數的一半，我們發現此現象是因為探針無鍍金屬，依據針尖的形狀接收不同高度的光場疊加後的結果。相同的分析技術也用在L3結構光子晶體中，也探討品質因子最高的模態在缺陷的空間分佈。最後，在奈米尺度的量子點樣品中，透過量測金屬銦與量子點的光學性質的差異，提供辨別金屬銦存在的有效方法；由氮化銦鎵量子點的近場影像與形貌可知，銦組成較高的大顆量子點稀疏地分布在表面，銦組成較低的小顆量子點密度高且均勻地平舖在樣品表面，這是由於相分離造成銦組成的不均勻所造成。利用掃描式近場顯微術，我們能從微米與奈米尺度半導體樣品的高解析度影像，有效地研究樣品的微觀光學性質。

Scanning Near-field optical microscopy (SNOM) with high resolution was used to study optical properties in microdisks, photonic crystals, InN and InGaN dots. Finite difference time domain (FDTD) simulation confirm the experimental results. Near-field image show the number of whispering-gallery modes (WGMs) azimuthal intensity maxima around the disk circumference is half number by simulation. It is because of the image is collected from different part of uncoated tip. We also observed the spatial distribution of resonance mode which is highest quality factor in L3 photonic crystal. Finally, we could identify In droplet in InN dots by SNOM because of different optical property. The relation between composition and dot size in InGaN is also found by near-field image and surface morphology. Phase separation in InGaN dots result in different indium composition dots. SNOM is a powerful tool to research semiconductor micro and nano scale structures.