Effect of substrate on the growth and properties of thin 3R NbS2 films grown by chemical vapor deposition

The effect of substrate (c-plane sapphire versus epitaxial graphene/6H-SiC) on the CVD growth and properties of thin 3R NbS2 films was investigated using niobium (v) pentachloride (NbCl5) and hydrogen disulfide (H2S) as precursors in a hydrogen carrier gas. The growth temperature ranged from 400 °C to 800 °C and the sulfur to niobium ratio (S/Nb) ranged between 640 and 5100 under 100 Torr total pressure. Growth on sapphire resulted in fine grained nanocrystalline NbS2 films under all conditions studied whereas smooth NbS2 films with triangular-shaped domains, on the order of 1-2 μm in size, were obtained on epitaxial graphene under identical conditions. The differences in growth morphology were attributed to enhanced surface diffusion of Nb adatoms on the passivated graphene surface compared to that of c-plane sapphire. This work demonstrates that the substrate choice plays a very crucial role in the deposition of 3R NbS2.