Disorder-Induced Low-Frequency Raman Band Observed in Deposited MoS2 Films

Crystalline disorder in thin films plays an important role in determining their properties. Disorder in the crystal structure of MoS2 films prepared by magnetron sputtering and pulsed laser deposition was evaluated with the use of Raman spectroscopy. The peak positions and bandwidths of the first-order Raman bands, in the region 100 to 500 cm−1, were used as a measure of crystalline order. In addition, a low-frequency feature was observed at 223 cm−1 that is not part of the normal first-order spectrum of a fully crystalline specimen. Data presented here demonstrate that this band is characteristic of crystalline disorder, and its intensity depends on the annealing history of the film. This behavior seems to be analogous to the disorder found in graphite thin films.