雙原子分子在半導體表面孤立懸鍵上的吸附研究

Abstract

本論文主要在研究氣態雙原子分子化學吸附於半導體表面懸鍵(dangling bond)上的化學物裡動力學機制，並探討氣體分子在表面化學吸附過程中的分子裂解、原子移動、取代鍵結等現象。我們藉由微細探針引發脫附、熱脫附或控制曝氫量的方法於覆氫矽晶(100)表面產生成對和孤立的懸鍵，之後於此表面釋放氯氣體分子，再利用掃描穿襚顯微鏡(Scanning Tunneling Microscopy, STM)，直接觀測比較氣體分子吸附前後之原子解析度影像來研究這些現象。 本論文中實驗以選擇氯氣體分子和矽(100)-2´1:氫表面為具體研究對象。實驗結果顯示，氯雙原子氣體分子在懸鍵上的化學吸附有兩種可能的結構，一種為氯雙原子氣體接近孤立的懸鍵時，造成電子雲的轉移使得一顆氯原子鍵結於氫-矽-矽-樣品表面形成氫-矽-矽-氯的鍵結；另一種因成對懸鍵產生時，將造成微弱π鍵形成，因此容易被氯原子打斷而鍵結，形成氯-矽-矽-氯化學吸附，然而在掃描穿襚顯微鏡掃描的圖像也可以清楚地看到兩顆氯原子吸附在矽-矽雙原子單體(Si-Si dimer)上。

We have observed gaseous diatomic molecule on the semiconductor surface with the chemical-physics dynamic mechanism of the chemical adsorption on the dangling bond. We explored on the phenomena in how gas molecules dissolve, how the atoms move, and on how they replace the bondings during the chemical adsorption process on the surface. By using ultra-thin scanning tip we can form desorption, or by thermal desorption and controlling the exposure of hydrogen as methods to create the paired and unpaired dangling bonds on the Si(100) surface, then we exposed gas molecules on the surface and used scanning tunneling microscopy to observe the phenomena in comparing the gas molecules before and after the adsorption with the atomic scale images. In the experiment we chose chlorine gas molecules on Si(100)-2x1:H surface as our research object. From the results shown, there were two possibilities in the structure of chemical adsorptions of gas molecules on the dangling bonds; one of them being when diatomic gas molecules come near the unpaired dangling bonds, they cause a shift in the electron cloud, forcing one chlorine atom to bond on the H-Si-Si sample surface forming H-Si-Si-Cl bonds; the other was when paired dangling bond forms, will cause the formation of weak bonds, so it will be easily broke by the chlorine atoms to form bonds, becoming Cl-Si-Si-Cl chemical adsorption. However, from the scanned STM images we can clearly see the two Cl atoms adsorbing on the Si-Si diatomic dimers.