Transition metal dichalcogenides (TMDCs) are semiconductors of the type MX2, where M is a transition metal atom (such as molybdenum or tungsten) and X is a chalcogen atom (such as sulphur, selenium, or tellurium). TMDCs provide a promising alternative to graphene as a 2-D, atomic scale material for use in electronics, battery, and semiconductor industries. TMDCs exhibit a unique combination of atomic-scale thickness, direct bandgap, strong spin–orbit coupling, and favorable electronic and mechanical properties, which make them interesting for research and for applications in high-end electronics, spintronics, optoelectronics, energy storage, flexible electronics, DNA sequencing, and personalized medicine.
Even though 2-D TMDCs exhibit a breadth of new properties that are distinct from traditional bulk materials or thin films, developing such materials into large-scale and defect-free atomic layers with controllable thickness on desired substrates is challenging. The state-of-art mechanical exfoliation method produces high quality monolayers of TMDCs, but this technique is not scalable. Likewise, electron beam lithography with etching creates pillars of material that limit its use in device fabrication.
Army researchers have developed a method for controlled and abundant growth of TMDCs by applying a focused ion or electron beam onto an insulator substrate, to produce a charged area on the surface. The charged surface is exposed to water molecules to hydrogenate the charged species, which is then subject to chemical vapor deposition in a tube furnace to grow thin, consistent layers of TMDCs.
- Simple, one-step surface modification process that allows nucleation seeding of TMDCs
- Avoids the use of toxic lithography chemicals
- The shape, size, or thickness of the TMDC film can be controlled by chamber pressure and temperature, metal source, concentration, type of surface, or combinations of these factors
- US patent 9,620,665 available for license
- Publication: Growth Mechanism of Transition Metal Dichalcogenide Monolayers: The Role of Self-Seeding Fullerene Nuclei. ACS Nano, 2016, 10 (5), pp 5440–5445
- Potential for collaboration with Army researchers