Synthesis and Characterization of Two-Dimensional Transition Metal Dichalcogenides, Alloys, and Heterojunctions Over Various Substrates via Chemical Vapor Deposition
- Author(s): Barroso, David
- Advisor(s): Bartels, Ludwig
- et al.
Interest in two-dimensional (2D) electronic materials has exploded in the past decade, starting with the isolation of single layer graphene in 2004 by Novoselov.1, 2 Similar to graphene, as a stable material in the single-layer, transition metal dichalcogenides (TMDs) further the advancement of 2D materials, but also provide an intrinsic transition to a direct bandgap in the single layer,3, 4 thus giving these materials an advantage over graphene. Furthermore, TMDs have some of the highest notable Ion/Ioff ratios of other 2D materials, making them extremely favorable.5, 6 However, none of these 2D materials can be used as a standalone for modern electronic applications, therefore, heterostructures of these materials must be created.7-11 An understanding of the way these materials are synthesized and ways to manipulate the synthesis is necessary to achieve such structures. Chemical vapor deposition (CVD) is a commonly used method to create single-layer TMDs12-18 among others such as mechanical exfoliation19, 20 and metal sulfurization/selenization.21, 22
Here I present facile methods by which to synthesize pristine, pure, 2D TMDs via CVD process manipulation.19 Additionally, in-situ operation of the CVD furnaces leads to the ability to alloy these materials and create heterostructures, leading to a study of tunable optical and physical properties.12, 22, 23 Last, I show the use of various/nanofabricated features on growth substrates in order to lead to a deeper understanding of the growth mechanisms for TMDs.14, 24-26