Raman and TEM characterization of 2D layered MoS₂ crystals grown on non-metal surfaces by friction-induced synthesis

Thin films of crystalline molybdenum disulfide (MoS₂) are grown by friction-induced synthesis at the interface between a n⁺-Si(1 0 0) substrate and a synthetic quartz ball. The thin films are formed as a result of the tribochemical reaction of molybdenum dithiocarbamates (MoDTC) in synthetic oil under sliding friction conditions. Raman mapping shows the width of the grown MoS₂ film to be about 7 µm, and the difference between the Raman frequencies of the E¹_2g and A_1g modes indicate that there are more than 6 monolayers in the MoS₂ film. A TEM image indicates that a layer-by-layer structure is formed at the top surface of the stacked films. These results show that it is possible to fabricate a 2D layered MoS₂ film on a non-metal surface using this friction induced crystal growth method.