M.Sc Student | Ben-Melech Stan Gabriela |
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Subject | Lateral Interface in Two-Dimensional Transition Metal Dichalcogenide Metal/Semiconductor Heterostructures |
Department | Department of Materials Science and Engineering | Supervisor | Professor Maytal Caspary-Toroker |
Full Thesis text | ![]() |
In our present study, we used TMD monolayers to design a novel metal/semiconductor heterojunction for nanoscale applications, such as an all-2D-transistor. Using VASP, an ab-initio simulation program suitable for DFT calculations, we scanned a dozen of different TMD monolayers and computed their structural constants and energy band alignment. Based on these results, six optimal metal/semiconductor heterojunctions were composed: FeS2/MoS2, FeS2/WS2, FeS2/CrS2, VS2/MoS2, VS2/WS2, and VS2/CrS2. The quality and performance evaluation of each heterojunction was based on the following calculated characteristics: structural mismatch between metal and semiconductor monolayers, Schottky barrier height, adhesion energy of the interface, projected density of states, existence of metal-induced-gap-states (MIGS) along the semiconductor, potential energy, and charge density differences though the junction.
We noticed that all the monolayers composing the heterojunctions form a strong covalent bond at the interface expressed by a strong hybridization between the transition metals d-orbitals on both sides of the interface, combined with a high adhesion energy of the interface. In addition, we found that VS2/ CrS2 heterojunction is especially interesting since it has a neglectable Schottky barrier for hole transport, low potential energy barrier at the interface, and CrS2 has a high charge density around Fermi level. Moreover, monolayer CrS2 has a direct bandgap of 0.9eV, which is close to that of Silicon (1.1eV), which is widely used as the channel semiconductor in transistors.
Metal/semiconductor interfaces based on 2D-TMD both as the metal and semiconductor possess great potential in terms of performance control. High quality fabrication and defect free interface can be expected due to the low mismatch and similar chemical characteristics of the materials. Also, as showed in this study, TMD monolayers can produce metal/semiconductor interface with few and highly localized MIGS.