Correlation of Processing Variables with Properties of Two-dimensional Tungsten Diselenide Fabricated via Metal Organic Chemical Vapor Deposition
Open Access
- Author:
- Hossain, Lorraine Amena
- Area of Honors:
- Materials Science and Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Joshua Alexander Robinson, Thesis Supervisor
Elizabeth Rader Kupp, Thesis Honors Advisor - Keywords:
- materials science & engineering
synthesis
thin film
2D materials
analysis & characterization
electronic & optical materials - Abstract:
- Novel two-dimensional materials like WSe2 display optimal properties for faster and more efficient electronic and optical devices. More efficient electronic devices derived from the tunable band gap of these transition metal dichalcogenide materials will see improvements in the National Academy of Engineering’s (NAE) Grand Challenges of health informatics and virtual reality. For the research contained in this thesis, a series of experiments was conducted, varying the substrate material, the pressure, temperature, duration, and gas flow ratios of the system during growth, and the cleaning process to prepare each substrate. The WSe2 films are synthesized onto the various substrates via metal organic chemical vapor deposition, in which a precursor vapor is passed over the substrate with a carrier gas and forms the film from the heat and set pressure. The quality of the resulting WSe2 film was analyzed via Raman spectroscopy, atomic force microscopy, photoluminescence, and field emission scanning electron microscopy. The analysis demonstrated that increasing the pressure of the chamber from 600 Torr to 800 Torr decreased the nucleation of triangles while increasing the domain size of triangles. Additionally, an increased growth temperature from 600 °C to 900 °C also decreased the nucleation density with an increase in domain size. The ratio of selenium to tungsten precursor also affected the synthesis, with lower selenium concentrations creating selenium deficiencies and tungsten-rich precipitants on the surface. With the sapphire substrate, films with about ten micron WSe2 triangles were synthesized. The boron nitride substrates exhibited a different growth mechanism, screw dislocation, and produced smaller domain sizes than sapphire substrates grown under the same conditions.