單層鉍化銦在Si(111)晶面的成長與原子結構

Structure and Growth Mode of the Single Indium-Bismuth Atomic Layer on the Si(111) Surface

黃育璋(Huang, Yu Zhang)

指導教授 ： 林登松

國立清華大學/理學院/物理學系/碩士(2016年)

摘要

近年來單層以及數個原子層二維材料逐漸受到重視，二維材料與一般工業界常用的矽晶基板不同之處在於，二維原子層平面間原子以共價鍵形成網狀結構，而層與層之間則是凡德瓦力(Van der Waals force)鍵結。拓樸絕緣體(topological insulator)近幾年同樣受到學術界重視，拓樸絕緣體最奇特之處在於內部屬於絕緣體，而表面或是邊緣處自旋電子具備導電性質。
最近一些Ⅲ-Ⅴ族化合物薄膜被預測具備二維拓樸絕緣體性質，因此本實驗藉由分子束磊晶(Molecular beam epitaxy)方式將In與Bi沉積於Si(111)表面接著進行熱退火處理，並透過X-ray光電子能譜技術觀察In與Bi鍵結情形以及掃描式穿隧電子顯微技術探測表面形貌以及原子結構。X-ray光電子能譜術含有三組實驗：(1)先成長Bi薄膜接著室溫蒸鍍In (2)先成長In薄膜接著室溫蒸鍍Bi (3)室溫同時蒸鍍In與Bi，三組實驗最後皆進行退火處理，於450℃明顯看出In與Bi有內殼層電子位移的現象，因此推測In與Bi在此狀態產生鍵結；掃描式穿隧電子顯微術實驗中利用室溫同時蒸鍍In與Bi比例1：1 曝量0.5 ML：0.5 ML、1 ML：1 ML以及2 ML：2 ML再進行退火處理於425℃以及480℃退火後成長√7 × √7-InBi 薄膜，最高覆蓋率可達73 %。綜合兩種不同實驗方法得知400℃ ~ 500℃為√7 × √7-InBi成長溫度。
　　本實驗成功藉由分子束磊晶方式再透過熱退火處理成長√7 × √7-InBi薄膜，但是InBi是否具備二維拓樸絕緣體性質仍有待確認，若具備此性質在邊緣處電子態密度會有劇烈變化，因此這方面可藉由掃描探針顯微術加以驗證。若為二維拓樸絕緣體，透過角分辨光電子能譜學(ARPES)分析能帶結構得知能隙大小，進一步確認運用於科技產品的可能性。

關鍵字

鉍化銦 ； 矽(111) ； X-ray光電子能譜技術 ； 掃描式穿隧電子顯微術 ； 鉍 ； 銦

並列摘要

In recent years, researchers pay lots of attention to two dimensional (2D) materials with single atomic layer and multi-layers. The difference between 2D materials and the widely-used silicon substrates is that atoms in 2D atomic layer form networks by covalent bonds in plane, but the bonding between layers is by Van der Waals force. Besides two dimensional materials, topological insulators (TI) have also attracted much interests. The TI’s interior behaves as an insulator, but its surface or edge have conducting states due to spin-orbital interactions.
　　Some Ⅲ-Ⅴ compounds including InBi and GaBi have been recently predicted to be two dimensional topological insulator recently. Therefore, we use molecular beam epitaxy (MBE) method to deposit Indium (In) and Bismuth (Bi) on the Si(111) surface, with subsequently thermal annealing. We utilize synchrotron radiation to observe the core-level spectra of Si, In and Bi and use Scanning tunneling microscopy (STM) to observe the surface topography and atomic structure of the grown films. Three experiments have been performed : 1. to grow a Bi layer first followed by In deposition at room temperature (RT), 2. to grow an In layer first and followed by Bi deposition at RT, 3. co-deposition of In and Bi at RT. We have observed core level shift at 450℃ during post annealing for In 4d and Bi 5d, suggesting the formation of In-Bi layer. In the STM measurement, we co-deposited at RT In and Bi with various In:Bi ratios: 0.5 :0.5 ML, 1.0 :1.0 ML, 2.0 :2.0 ML. We observed √7 × √7-InBi film growth after annealing at 425℃ and 480℃. The highest coverage of the √7 × √7-InBi domains achieved about 73 %. Combining results from the two complementary techniques, we concluded that √7 × √7-InBi layer can be grown between 400℃ to 500℃.

並列關鍵字

InBi ； Si(111) ； X-ray photoemission spectroscopy ； Scanning tunneling microscopy ； Bi ； In

參考文獻

[3] L. Z. Yao, C. P. Crisostomo, C. C. Yeh, S. M. Lai, Z. Q. Huang, C. H. Hsu, F. C. Chuang, H. Lin, and A. Bansil, Scientific reports 5, 15463 (2015).

[4] W. A. Harrison, Surface Science 55, 1 (1976).

[7] H. HUANG and S. Y. TONG, Phys. Lett. A 130, 166 (1988).

[9] A. ICHIMIYA, Surface Science 192, L893 (1987).

[12] C. P. Crisostomo, L. Z. Yao, Z. Q. Huang, C. H. Hsu, F. C. Chuang, H. Lin, M. A. Albao, and A. Bansil, Nano letters 15, 6568 (2015).