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Thesis
The effect of metal halides on MoS₂ growth by chemical vapor deposition
Master of Science (M.S.), Drexel University
May 2018
DOI:
https://doi.org/10.17918/ns4d-1f71
Abstract
Two-dimensional (2D) materials are materials in which the crystal structure is arranged only along two dimensions. The first 2D material to be fabricated was graphene, and it has been studied intensively for its unique band structure and excellent mechanical properties. Transition metal dichalcogenides (TMDs) are another type of 2D material that has a sandwich structure where a layer of transition metal atoms is situated between two layers of chalcogen atoms. MoS₂, an example of TMDs, is the most studied 2D material because of the transition from indirect to direct bandgap when the layer number decreases. Chemical vapor deposition (CVD) is a widely used technique to synthesize 2D MoS₂. Large-scale thin films can be obtained from this method; however, a limitation of CVD is that the reaction temperature required for growth is high (~800 °C). In this work, I synthesized MoS₂ on SiO₂ with the assistance of different alkali metal halides (NaCl, NaF and NaBr) at reduced temperatures through CVD, and characterized the properties of the films with optical microscopy, Raman microscopy, photoluminescence and atomic force microscopy. I show that alkali metal halides can reduce the growth temperature of MoS₂ from 850 °C to 750 °C, and different alkali metal halides have different effects. The thickness of MoS₂ synthesized with the assistance of NaCl at 750 °C is close to bulk, while the thickness of MoS₂ synthesized with the assistance of NaBr and NaF at 750 °C is monolayer. However, the size of the films synthesized with the assistance of NaF at 750 °C is much smaller than that with NaBr, indicating that NaBr is the most suitable precursor that can be used to lower the reaction temperature while maintaining the crystalline quality at the investigated conditions. By demonstrating a means to reduce the CVD growth temperature, this work has a potential to advance synthesis of MoS₂ on temperature-sensitive substrates.
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Details
- Title
- The effect of metal halides on MoS₂ growth by chemical vapor deposition
- Creators
- Zizhao Chen - DU
- Contributors
- Steven J. May (Advisor) - Drexel University (1970-)Jonathan E. Spanier (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Master of Science (M.S.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- 57 pages
- Resource Type
- Thesis
- Language
- English
- Academic Unit
- Materials (Science and) Engineering (Metallurgical Engineering) [Historical]; College of Engineering (1970-2026); Drexel University
- Other Identifier
- 8238; 991014632281904721