The STM Study of Bi Adsorption on the InAs(111)B Surface

Sammanfattning: Semiconductors composed of group III and group V elements have a variety of promising applications, such as topological insulators and quantum computers. Among this category of semiconductors, bismuth (Bi)-containing III-V compounds are able to make these applications possible. However, the difficulty was found to alloy Bi atoms into the host lattice. To solve the problem of material fabrication, we need to understand how Bi atoms affect the structure of the host material. In this thesis, we chose to study the Bi adsorption on the indium arsenide (InAs) (111)B surface. Bi atoms were evaporated from a solid source, and deposited on the InAs(111)B surface. Scanning tunneling microscopy (STM) was used to investigate the surface morphology, as well as distinguish the difference between different deposition durations and the effect of annealing. From STM images, we found that deposited Bi atoms tend to scatter around as single atoms, and then aggregate into small islands. The growth of Bi films were prohibited due to the short diffusion length on the substrate, since the deposition was done at room temperature. In addition, we also found Bi-induced substrate reconstruction after the deposition. From deposition tests, we noticed that the Bi morphology is sensitive to experimental parameters, such as the Bi source temperature. Thus, the key to improve the reproducibility of the results is the precise control over the source temperature. After annealing the Bi-deposited substrate, the number of Bi clusters decreases significantly, meanwhile, some holes were left on the surface. Our study is just the rst step of understanding the Bi adsorption behavior. The next step will be combining the STM results with other techniques to obtain quantitative and structural information of the surface. Also, the adsorption on nanowires (NWs) is of high interests, since the large surface-to-volume ratio of NWs may exhibit highly different properties from the surface of a bulk.