Wafer-scale deposition of transition metal Dichalcogenide film

• Main Author: Ang, Nicole Ru Xuan
• Other Authors: Tay Beng Kang
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Electrical and electronic engineering::Semiconductors
• Online Access: https://hdl.handle.net/10356/157973
• Institution: Nanyang Technological University

In today’s world, two-dimensional (2D) materials have gained huge popularity and interest due to their potential use in a variety of applications, such as electronic, optoelectronic, gas sensing, and energy storage devices. Layered transition-metal dichalcogenides (TMDs) is a key player in 2D materials research. 2D TMDs possess numerous outstanding material properties such as ultrathin nature, high flexibility, high mechanical strength, unique optoelectronic properties, a layer-dependent adjustable band gap coupled with indirect-to-direct band gap transition present in the monolayers, and intense photoluminescence. They are therefore deemed suitable for implementation in optoelectronics and electronics applications. There is a high motivation for successful TMDs integration into commercial applications, which has in turn created a critical demand for obtaining high-quality, electronic-grade monolayer TMDs with homogenous film continuity on large surfaces. This project focusses on molybdenum disulfide (MoS2), a notable example of 2D TMDs. Monolayer MoS2 possess unique and outstanding properties such as a wide direct bandgap (~1.8 – 1.9 eV), high carrier mobility (~ 200 cm2V-1s-1), and high thermal stability, making it suitable for use in the fabrication of field effect transistors with low static power consumption, high efficiency and high on/off ratios. MoS2 devices can also overcome the short-channel effects faced by silicon (Si) devices in the nanoscale level, making it a possible substitute material for Si. In this project, wafer-scale monolayer MoS2 samples were first be prepared via material deposition with chemical vapor deposition (CVD) synthesis, while varying the deposition parameters. Next, material characterization using techniques such as Raman spectroscopy, photoluminescence (PL) spectroscopy and electrical test were conducted to analyze the structural properties, optical properties, and quality of the MoS2 synthesised. Based on the results, further optimisation of the deposition parameters was carried out to improve the quality of the MoS2 films, and also thereby conclude on the optimal deposition parameters to be used, which is crucial for the implementation of wafer-scale monolayer MoS2 in electronic devices and applications. Keywords: 2D materials, TMDs, MoS2, CVD synthesis, wafer-scale