氯化鉀離子固體在矽晶上之介面研究

Abstract

本文研究KCl薄層在0.4-ML-Ge/Si(100)-2□1上的生成與熱脫附反應。在室溫下於Ge/Si(100)-2□1表面上飽和吸附Cl2氣體，接著在Ge/Si(100):Cl表面上蒸鍍上鉀，之後再加熱。實驗是利用同步輻射，以核心層光電子激發術觀察樣品表面的原子結構。由Ge 3d、K 3p和Cl 2p核心層光電子譜及價帶光電子能譜的變化可以得知在0.4-ML-Ge/Si表面曝滿Cl2氣體，則Cl原子與表面產生Si-Cl和Ge-Cl鍵結，而蒸鍍上K之後，Cl和表面的Si-Cl和Ge-Cl鍵結消失，同時Cl和K鍵結形成KCl離子固體薄層在表面上且此薄層與表面沒有電子轉移現象而為類似地毯附著在表面。在325K-665K，熱脫附產物為KCl，至665K，表面已經沒有KCl薄層，而不管K蒸鍍量多或少，加熱至950K的高溫，都還會有微量K沉積散佈在矽表面下，不容易被熱脫附。另外我們還做了HCl在Si(100)-2×1表面上的熱反應實驗，當溫度超過605K，部分原有樣品表層Si的雙原子單體結構被打斷，使部分的Si與兩個Cl鍵結，而原來以雙原子單體鍵結的另一相鄰Si因擠壓而未有Cl與之鍵結，隨樣品溫度升高以Cl-Si-Cl鍵結方式的Si數目增多，至溫度為915K時此溫度開始時Si-Cl及Cl-Si-Cl都出現了Cl脫附現象，且Cl的脫附為以SiCl2為主的方式脫附。另外加熱溫度至650K時，H原子就開始從表面上重新結合成H2分子熱脫附。

The thesis describes the growth of potassium chloride(KCl), and its thermal reactions on the Ge/Si(100)-2□1 surface. Synchrotron radiation was used to excite the Ge 3d、K 3p、Cl 2p photoemission electrons. When Cl2 was exposed onto the Ge/Si(100)-2□1 surface, Cl2 molecules dissociate and chemisorb on surface, and form both Cl-Si and Cl-Ge bonds. The KCl films were obtained by evaporating potassium on the Cl-terminated Ge/Si(100) surface at room temperature. The Cl-Si and Cl-Ge bonds disappears after potassium adsorption. The valence bands spectra indicates that Cl and K become KCl ionic solid on the Ge/Si(100) surface. Annealing the samples to temperature above 325K, KCl desorbs from the Ge/Si(100) surface. At 665K, the KCl thin layer is gone. Small amount of potassium tends to diffuse into the subsurface. Additionally, we studied the thermal reactions of HCl on the Si(100)-2x1 surface. Some Si-Si dimer was broken by chlorine at 605K, so that a part of Si-Cl bonds were replaced by Cl-Si-Cl bonds. Above 915K, Cl gradually desorbs from the Si(100)-2x1 surface via SiCl2 desorption.