矽(111)基板上製備純粹的鉍-α(√3×√3)表面

Preparation of Pure Bi/Si(111)–α (√3×√3) Phase

謝世慶(Shih-Ching Hsieh)

指導教授 ： 林登松

國立清華大學/理學院/物理學系/碩士(2018年)

摘要

鉍原子於矽(111)基板上有 兩種(√3×√3) R30˚超結構: α及β相，此兩種超結構差別為單位晶包內鉍原子的數目。β結構為鉍三聚體(trimer)所組成，其製備方式及相關電子特性如Rashba效應皆已被廣泛的研究；α結構則是由鉍原子吸附於矽(111)之T4位置形成之鉍原子單體，然而相關文獻中一直無法給出明確的製程說明，也造成α結構尚未被深入的討論研究。在本論文中，以掃描穿隧電子顯微鏡(STM)觀察兩種結構之成長模式，並繪製鉍原子鍍量與加熱溫度之相圖，嘗試找出製備 α- (√3×√3)R30˚單原子層之標準作業程序。實驗結果顯示：直接蒸鍍1/3ML鉍原子於矽基板後加熱，並無法形成大面積的α結構，必須透過熱脫附的方式，對鉍原子個數較多的 β結構進行熱退火，且溫度須達到500˚C並維持三分鐘，使β相中的鉍原子脫附而成長出了1ML的α相結構，接著以此兩種超結構表面為基礎，使用STM去量測兩者間的結構差異及比較其電子能態。

關鍵字

矽(111) ； 鉍

並列摘要

Bismth on Si(111) substrate has two super structure: α and β phase. Both of them show a (√3×√3) R30˚ reconstruction .The most difference between these two super structure is the number of bismuth atoms in an unit cell. β phase is trimer of bismuth atoms, which has been well studied, including the preparing method and the electronic properties, e.g. rashba effect. Compare with α phase, single bismuth atom standing on T4 site. Barely could find the specific fabrication method or phase diagram from literature. Therefore, α phase haven’t been discussed or researched in experiment widly. In this thesis, we use the scanning tunneling microscopy to observe the growth mode of α and β phase. Using the experiment data to make a phase diagram and tring to find out the standard operation procedure for α phase. The experiment results reveal that we couldn’t obtain α(√3×√3) R30˚ atomic layer by depositing 1/3ML Bismuth on substrate then post annealing directly. The technique of thermal desorbtion is nessceary under the process. To get a well-fromed α phase surface. First, prepare 1ML β phase and post anneal to 500˚ C for at least three minutes. While the bismuth atoms desorbing, α phase appearing at the same time. By contral the desorbed time, we could prepare 1ML α phase. And then, base on these two super lattice, α and β phase. Utilizing the STM to measure their density of state and observe the structural differeces.

並列關鍵字

Si(111) ； Bi ； α

參考文獻

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