Abstract
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℃.