鉛蒸鍍於Si(111)-(5×2)/Au表面時對表面上的亮點造成的影響

Effect of Pb Deposition on Bright Protrusions at Si(111)-(5×2)/Au Surface

陳家麟(JIA-LIN CHEN)

指導教授 ： 門福國

國立中正大學/理學院/物理學系/碩士(2016年)

摘要

蒸鍍0.5 ML (monolayer)的金原子在Si(111)-(7×7)表面時，我們可以觀察到(5×2)重構，儘管經過很多年許多學者的努力下Si(111)-(5×2)/Au原子結構的細節仍然是個謎。為了了解這個令人驚訝的複雜結構，我們選擇兩種不同的方法來研究這個表面的特性，一種為蒸鍍與矽同為4A族的鉛原子到表面上;而另一種方法為施加外部應力在表面上，觀察外部應力對表面結構造成的變化。掃描穿隧式顯微鏡(STM)被用來觀察表面的形態變化。
　　鉛蒸鍍在(5×2)表面後，除了觀察到鉛原子會坐落在空缺的Si adatom位置上，我們也可以發現Si adatoms會被鉛原子取代。當取得了鉛蒸鍍於(5×2)表面的掃描穿隧能譜(STS)數據，可以詳細比較不同鏈長的Si-Si, Pb-Pb, Si-Pb原子鏈在填滿態、空乏態的局部能態密度。
　　施加外部拉伸應力在Si(111)-(5×2)/Au表面，我們可以觀察到隨著施加應力提高則Si adatom密度會減少。施加外部拉伸應力在Si(111)-(5×2)/Au/Pb表面後，Si adatom密度會稍微增加，而Pb adatom密度則減少的較快，目前我們沒有任何一個模型考慮到這個非常有趣的現象。

關鍵字

矽(111)-(5×2)/金 ； 矽(111)-(5×2)/金/鉛 ； 掃描穿隧式顯微鏡 ； 掃描穿隧能譜 ； 局部能態密度

並列摘要

By depositing 0.5 ML (monolayer) of Au atoms on Si(111)-(7×7) surface we have observed a (5×2) reconstruction. Despite of efforts put out by many researchers through the years, the detailed atomic structure of Si(111)-(5×2)/Au is still a mystery. To understand this surprisingly complicated structure we have chosen two different approaches to investigate the properties of this surface, one is to deposit Pb atoms, also a column IV element, on this surface and the other is to apply external stress to observe the change in surface structure resulting from the external stress. Scanning tunneling microscopy (STM) is utilized to observe surface’ morphological changes.
　　After Pb deposition on a (5×2) surface, in addition to Pb atoms taking vacant Si adatom sites, we have also observed the replacements of Si adatoms by Pb atoms. Scanning tunneling spectroscopy (STS) data have been acquired on this Pb deposited (5×2) surface. Detailed comparisons of local density of states for filled and empty states between Si-Si, Pb-Pb, and Si-Pb adatom chains have been performed for a range of chain lengths.
　　By applying an external tensile stress to a Si(111)-(5×2)/Au surface, we have observed a monotonic decrease in Si adatom density with respect to the increase of the applied tensile stress. After applying tensile stress to a Si(111)-(5×2)/Au/Pb surface, however, the Si adatom density increases slightly whereas the Pb adatom density decreases relatively quickly. At present time we do not have a model to account for this intriguing phenomenon.

並列關鍵字

Si(111)-(5×2)/Au ； Si(111)-(5×2)/Au/Pb ； STM ； STS ； LDOS

參考文獻

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