由氯的吸附與脫附觀察Si/Ge(100)-2×1表面的原子結構

Abstract

本文研究Si/Ge(100)-2×1表面上，氯的吸附、熱反應與原子排列結構的變化，Ge(100)-2´1表面上的Si分別為0、0.9、1.4、4.2和12ML(monolayer)。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、Si 2p和Cl 2p核心層光電子譜的變化可以得知，當成長Si到Ge(100)-2×1表面上時，Si原子會沈積到Ge(100)-2×1表面下，樣品表面全都被Ge原子覆蓋，形成Ge-Ge雙原子單體結構。曝氣Cl2氣體到Si/Ge(100)表面上，樣品表面只有Cl-Ge鍵結。加熱使樣品溫度升高時，表面的Cl會產生熱脫附現象。樣品加熱溫度在550–680K時，樣品表面的氯以GeCl2的形式脫附，而樣品加熱溫度在680–730K時，樣品表面的氯則是以SiCl2的形式脫附。當加熱樣品使一部份的Cl以GeCl2的形式從樣品表面脫附後，此時Cl 2p 核心層光電子譜出現了Cl-Si鍵結，同時Cl-Ge鍵結消失，顯示在熱脫附發生過程中，表面層的Ge、Si原子位置發生交換反應。

The thesis describes the chlorine adsorption, thermal reactions and the atomic structure on the Si/Ge(100)-2×1 surface studied by synchrotron core-level photoemission. The amounts of Si atoms deposited on the Ge(100) samples are 0, 0.9, 1.4, 4.2 and 12 monolayer(ML). Deposition of Si on the Ge(100) surface results in Si occupying the second layer and Ge floating on the surface. That is, surface is completely covered by Ge with the Ge-Ge dimer structure. After dosing Cl2 onto the Si/Ge(100) surfaces at room temperature, only Cl-Ge bonds are present on the surface. Annealing the sample to the temperature range of 550-680K, Cl partially desorbs from the sample surface. And the Si 2p and Cl 2p spectra show that the Cl-Si bonds replace the Cl-Ge ones. Therefore it is evident that the place exchange occurs between the Si atoms and the Ge atoms near the surface layer. The remaining surface Cl desorbs in the form of SiCl2 in the temperature range of 680-730K.