Structure and optical properties of 2D layered MoS₂ crystals implemented with novel friction induced crystal growth

We used X-ray diffraction, and Raman and photoluminescence (PL) spectroscopies to examine the structure and optical properties of molybdenum disulfide (MoS₂) crystals grown by friction at the interface between two materials. MoS₂ is produced chemically from molybdenum dithiocarbamates (MoDTC) in synthetic oil under sliding friction conditions. The X-ray diffraction (XRD) patterns indicate that the structure of the MoS₂ is layered with the c-axis perpendicular to the surface. The MoS₂ layer was formed on stainless steel and germanium by friction at the interface between these materials and high carbon chromium bearing steel. The number of layers is estimated to be N (N > 6) from the distance between the Raman frequencies of the E¹_2g and A_1g modes. For MoS₂ grown on stainless steel, exciton peak is observed in the PL spectrum at room temperature. These results show that this friction induced crystal growth method is viable for synthesizing atomic layers of MoS₂ at solid surfaces.