Molybdenum Disulfide (MoS2) belongs to a class of materials called Transition Metal Dichalcogenides (TMD). TMDs have the chemical formula MX2 where M is a transition metal such as Molybdenum, Tungsten, etc. and X is from the chalcogen group. After graphene, MoS2 is the next 2-dimensional material being researched for new device applications given its strong optical and electronic properties. Methods for producing MoS2 include micromechanical exfoliation, solvent exfoliation and intercalation. The challenge with these top-down approaches is that their size renders them unsuitable for electronic applications. Other processing methods may leave undesirable carbon residue.
Prof. Cengiz Ozkan and his research team at UCR have developed and synthesized atomically thin, large area MoS2 sheets. The patented technology synthesizes MoS2 sheets on SiO2/Si substrates at wafer scale by thermolysis of spin-coated, (NH42)2MoS4 films. They have also used this method to prepare WS2 (Tungsten Disulfide) and hybrid MoS2-WS2 thin layers.
High-angle, annular dark-field scanning, Transmission Electron Microscopy image showing tri-, bi- and monolayer MoS2 (from left to right).
The plot of drain current versus gate voltage for fabricated FET shows electron transport. The on/off ratio for this device is 300.
The benefits of their technology are:
- Excellent control of the film thickness by varying the concentration of the solution and spin coating speed.
- Does not need the use of sulfur or high temperatures for preparation.
- Can be used to achieve homogeneous alloys and doping of TMDs.
- Samples can be prepared down to monolayer thickness.
- Field effect transistors, high-efficiency switching and logic circuits
- Solar cells
- Chemical sensors
- Supercapacitor electrodes
- Next generation Valleytronics – e.g., quantum computing and qubits.
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