Investigation of Bismuth-Induced Surface Structures on InSb

Abstract

The investigation of Bismuth surface structures on InSb(110) surfaces is driven by the need to advance semiconductor technology for enhanced electronic device performance and new applications in optoelectronics and quantum computing. III-V semiconductors offer superior electronic properties compared to silicon. Incorporating Bismuth into these materials can significantly manipulate the bandgap, making them suitable for long-wavelength optoelectronic applications, and theoretical studies promise for these materials to behave as topological insulators with nearly lossless electron transport.

In this study, the evaporation and incorporation of Bismuth on InSb(110) surfaces is explored, focusing on the surface interactions and bonding states for bismuth evaporation at elevated sample temperature or at room temperature with subsequent annealing. Scanning Tunneling Microscopy (STM) is used to analyse the surface structure and X-ray Photoelectron Spectroscopy (XPS) to determine the chemical composition and bonding. Thereby, the STM studies show a local difference in the surface step density of the pure InSb surface. A higher step density is observed at the centre of the sample than at the edge, which is tied to an inhomogeneous distribution of strain during the sample cleavage or an inhomogeneous temperature distribution on the sample surface. The observed bismuth structures largely follow the underlying III-V lattice structure with a 1x2 reconstruction over large areas. However, bismuth islands independent of the substrate lattice are observed on the areas with a higher surface step density. During deposition at room temperature with subsequent annealing in a temperature range comparable to that of the STM sample, a 1x3 reconstruction was observed. The same was found with a sample that was heated during deposition to lower temperatures for a longer period of time. XPS data of the last two samples mentioned also show a difference in the types and amounts of Bi bonds. Thus, for subsequent annealing after deposition at room temperature, an increased amount of In-Bi bonds with respect to the Sb-Bi bonds are found, in comparison to the sample with deposition at elevated sample temperatures. Additionally, a higher stability of the amount of Bi on the surfaces under continued heating was observed in comparison to Bi deposition on a heated sample.

Consequently, it is discovered that the order of the treatment steps subsequently influences the type and amount of Bi bondings and the observed surface structure.

Popular Abstract

A Thin Layer of Bismuth atoms on a Semiconductor Substrate Semiconductors, crucial materials that lie between insulators and metals, play a vital role in all electronic devices. With the miniaturisation of electronic components, the importance of surfaces, interfaces, and thin layers has grown. III-V semiconductors, composed of elements from the third and fifth groups of the periodic table, are of particular interest as they are used in everyday electronics and also in many specialised products. Recent research has shown that incorporating bismuth into these semiconductors can significantly alter their properties. Bismuth can efficiently modify the material’s bandgap, a central property of semiconductors.This bandgap also influences the optical properties, such as the colour of light emitted by an LED or laser made out of this semiconductors. A thin bismuth layer on semiconductors like indium antimonide (InSb) is expected to exhibit unique electronic properties. These include the potential for spintronic applications, where electrons are separated by a quantum mechanical property called spin, and the formation of so-called topological insulators. These are materials that allow nearly lossless current flow, reducing device heating and energy consumption. When bismuth is deposited on the semiconductor, it can form bonds with itself and with the underlying atoms. These bonds significantly influence the material’s properties and the potential for forming a topological insulator. Theoretical studies suggest that bonds between bismuth and indium are promising for topological insulators. In this study, Scanning Tunnelling Microscopy (STM) and X-ray Photoelectron Spectroscopy (XPS) are used to investigate the properties of bismuth on the semiconductor, comparing deposition on heated samples and room temperature samples which are subjected to post-deposition heating. STM provides atomically resolved images of the sample’s surface, revealing its topography, enabling us to observe where the bismuth atoms are located on the semiconductor surface. This technique showed different bismuth formations on the surface within individual samples and between different treatment methods. XPS complements STM by ejecting electrons from atoms in the sample and measuring their energy. The energy depends on the chemical environment and bonding of the atom. By analysing the energy of the ejected electrons, we can infer the bonding nature of the atoms. This study observed that heat treatments increase the number of In-Bi bonds, which are crucial for the desired electronic properties.

• author: Ritter, Sina
• supervisor: Rainer Timm; Rohit Yadav
• organization: Atomic Physics; Department of Physics
• course: PHYM03 20241
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Physics and Astronomy
• keywords: semiconductor, surface science, bismuth
• language: English
• id: 9173428
• date added to LUP: 2024-09-03 11:01:55
• date last changed: 2024-09-03 11:01:55