Optimizing the Growth of WS2 Monolayers


Engineering and Applied Sciences


Project Summary

2D materials is an area of study that consists of crystalline materials made up of a single layer of atoms/molecules. This subject area has experienced exponential growth in the past 15 years with the isolation and production of graphene (a monolayer of graphite), a product that is now used in abundance in semiconductors and electronics. A specific category of 2D materials is Transition Metal Dichalcogenides monolayers, also known as TMDC’s. A TMDC unit is made up of a transition metal bonded with two chalcogen atoms and their electronic, photoelectronic and mechanical properties have great potential for practical application. One of the main obstacles that needs to be overcome regarding these materials is figuring out an optimal way to fabricate these monolayers that is both efficient, precise, and inexpensive to scale up.

My specific project for the summer was working to optimize the growth of WS2 triangle-shaped monolayers for our lab using a method known as Chemical Vapor Deposition. In order to do this, I had to prepare hydrophobic 1 cm2 silicon substrates. I then precisely placed the substrates in a tube along with WO3 and Sulfur. The tube was then put in a multi-zone furnace where I would flush out the tube and increase the different temperature zones, heating its contents in order to facilitate a reaction. Ideally, by the end of the growth process a monolayer of WS2 would have been deposited on the surface of the substrates. In order to optimize the growth of these monolayers, I ran multiple trials of the process, adjusting different parameters such as pressure, temperature, time intervals, ratio and placement of reactants, etc.

While I was able to run many successful and applicable trials, I learned how the overall process was a complex one. As a result, the slightest deviance in furnace configuration or sample preparation would affect the trial in an evident and negative manner. More time than I expected was spent working on identifying these issues when they arose and remedying them to ensure the validity of our results. Another major lesson I learned was that patience is an essential part of conducting research. Whether it was while conducting my experiments, trying to identify problems in the experimental process, or working to optimize my results, I always needed to stay calm, patient, and focused on the goal I was trying to achieve. Overall, I now also have a better understanding of what research can entail. Being a part of a lab group, I saw firsthand how one functions. I was also able to learn about what other projects the group members were working on and how they all related as well as what a career in research could potentially entail. 

Optimizing the Growth of WS2 Monolayers