Chemical and Materials Engineering
Two-dimensional transition metal dichalcogenides (TMDs) are of interest because of their potential for use in transistors and sensors due to their unique electronic and optical properties, coupled with mechanical flexibility. The band gaps of TMDs differ depending on the transition metal and dichalcogenide, the thickness of the TMD, and the structure of the TMD. To be able to tune the electronic and optical properties of TMDs, thin transition metal layers of molybdenum, tungsten, and rhenium were deposited on a silicon substrate with a 200nm oxide layer using a magnetron sputtering chamber. The film thickness and structure, surface characteristics, and conductivity were measured using atomic force microscopy, scanning electron microscopy, and a voltmeter, respectively. The thin transition metal films were then sent to collaborators to be exposed to sulfur or selenium to form TMDs. The TMD heterostructure will then be characterized using an AFM, SEM and Raman Spectroscopy. Then, transition metal bilayers were formed by sequentially depositing the transition metals on the silicon substrate with a 200nm oxide layer using a magnetron sputtering chamber. The film characteristics were then determined using the same methods as the single transition metal layer. The transition metal bilayers were then sent to collaborators to be exposed to sulfur or selenium to form TMDs. The bilayer TMD heterostructure will then be characterized using an AFM, SEM and Raman Spectroscopy and its optical and electronic properties will be characterized. Specifically, the electronic band gap will be evaluated and compared to the values for the monolithic monolayers. By varying the order of TMD layers, semiconductors with different band gaps will be able to be produced. This would allow for greater tailorability of the TMD semiconductors for use in applications such as flexible transistors and molecular sensors.
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Benton, Anna K., "Metal Layer Architectures for 2D TMD Heterostructures" (2020). Honors Theses. 248.