標題: Ge/Si(100):Cl表面上Si、Ge原子交換的觀測
Observation og Si-Ge Place Exchange on the Cl-terminated Ge/Si(100) surface
作者: 潘祥元
shiang-yuan Pan
林登松
Deng-Sung Lin
物理研究所
關鍵字: 原子交換;矽;鍺;氯;Si;Ge;Cl
公開日期: 2000
摘要: 工業界常利用SiCl4、Si2Cl6…等含Cl之矽化合物來成長Si薄膜,或利用Cl2蝕刻Si晶體,因此研究Cl在矽晶上之物理與化學反應的研究相當受到重視;本文研究Ge/Si(100):Cl表面上的熱反應,實驗方法是利用同步輻射光源,以核心層光電子激發術得到Si 2p、Ge 3d及Cl 2p能譜。因為Cl活性強,與Si、Ge原子鍵結時會由Si、 Ge轉移電子,使Si-Cl與Ge-Cl鍵中Si 2p、Ge 3d之能譜分量相對束縛能對於內體分量之相對束縛能差變大而易於分析。我們於Si(100)表面沈積不同厚度的Ge薄膜,然後在此些樣品上飽和吸附Cl2,觀察樣品加溫時表面Cl的脫附狀況及與Cl鍵結的表層Ge與內層Si原子的交換。 在Si(100)上長不同厚度Ge時,Ge原子大都在樣品表面,當溫度在510至655 K左右,各樣品上Si鍵結的Cl之Cl 2p 能譜分量Cls增加,但與Ge鍵結的Cl 2p能譜分量Clg減少,顯示原來與Cl鍵結的表面層Ge原子與較內層的Si原子做交換,同時Si 2p 能譜分量Si+ 增加及Ge 3d能譜分量Ge+ 減少;這種原子交換是因為表層由Si與Cl鍵結的情形比Ge與Cl鍵結時表面能量為低,因此樣品溫度足夠高時,表層Ge原子獲得足夠的能量,與較內層的Si原子做交換;樣品溫度約為655-710 K時,表層與Cl鍵結的原子皆轉換為Si原子。當溫度高於710 K以上時,從Cl 2p能譜強度減少很快,顯示Cl的脫附情形更為明顯。實驗數據隨表層成長Ge原子的厚度增加Cl的脫附速率更快,當Cl開始脫附時,此時Si 2p能譜表面層分量並未出現,而Ge 3d能譜表面分量逐漸增加,因此可以得知當Cl脫附時,表層為Ge原子會比表層為Si原子時能量為低,因此氯完全脫附後,其表面與在Si(100)剛成長薄膜時的情形相同。
The thesis describes the observation of the exchange of surface Ge-Cl and Si-Cl bonds on the Cl-terminated Ge/Si(100) surface. We grew 0.4 ML、1.2 ML and 2.0 ML Ge on the clean Si(100) surface by atomic-layer epitaxy using Ge2H6 gas source. After Cl2 saturtation each surface atom bond to one Cl. Upon annealing the Ge/Si(100):Cl sample to higher temperatures, synchrotron radiation was used to obtain the Si 2p、Ge 3d and Cl 2p photoemission spectra. Between 325 and 510 K, the Ge/Si(100)︰Cl surface remains largely unchanged. When the samples were annealed to above 510 K, the Ge atoms bonded to Cl on the surface have enough activation energy to exchange with Si in subsurface layers, and all the GeCl species vanish near 655 K. Between 510 and 655 K, some Cl atoms desorb in the form of GeCl2, and above 655 K most Cl atoms desorb by SiCl2 desorption. When Cl atoms compeletely desorb, Si atoms on the surface without Cl bonding move into the subsurface and Ge-Ge dimmer again dominate the surface. Experimental results showed that the desorption temperature of SiCl2 decreases as the Ge coverage increases, indicating that the activation energy of the desorption is lowered by Ge atoms in the subsurface layers.
URI: http://140.113.39.130/cdrfb3/record/nctu/#NT890198015
http://hdl.handle.net/11536/66704
Appears in Collections:Thesis