MoS2 is a material in the class of ‘transition metal dichalcogenides’ (TMDCs) with a chemical formula MX2. The crystal structure has a triple plane of S atoms on each side of a hexagonal plane of Mo atoms. The S atoms are joined to the Mo atoms by strong covalent bonds but weak van der Waals forcing. The layers can be separated mechanically to form two-dimensional sheets of MoS2 and are therefore suitable for crystalline electronics applications such as transistors, photovoltaic cells and electrochemical storage devices.
Several potential methods for large-scale MoS2 deposition are being studied including chemical vapour deposition and thermal chemical vapor deposition. These processes are relatively cheap and easy to control.
In thermal chemical vapor deposition, a precursor containing molybdenum and sulfur is heated in a gas to a desired temperature, resulting in the formation of MoS2 films. The temperature and the precursor vapor pressure are controlled to ensure good quality.
The melting point of MoS2 is about 1185 degrees C. This is a very high melting point for the TMDCs which allows for excellent electrical properties and low temperature operation.
It also has a good thermal stability and a high density 4.80 g/cm3 at room temperature. Its low hardness of 1.0
The atomic layers of MoS2 have different electronic and quantum characteristics, which make them interesting for optoelectronics applications. A single MoS2 layer can absorb 10% of incident light with energy above its bandgap, which is 1000-fold higher than that in a bulk crystal. This can be used to generate a brighter and more efficient photoluminescence.