Nanostructured MoSx-based thin films obtained by electrochemical reduction

The in situ electrochemical deposition of nanostructured MoS_x (x = 1.5–1.7) based thin films on various substrates from aqueous solutions is reported. The as-deposited amorphous films transform on annealing into crystalline ones as revealed by a stepwise high temperature X-ray diffraction (XRD). Both Raman spectroscopy and XRD crystal structure analyses confirmed the formation of inorganic fullerene-MoS_x nanoparticles (IF-MoS_x). The as-deposited thin films have a featureless surface morphology, but after annealing either a nanotube or a nanorod structure along with numerous smaller nanoballs appear at the surface. An investigation by transmission electron microscopy unearths the presence of nanoballs, nanoribbons, and nanotubes throughout the annealed MoS_x thin films. The size of the nanoballs is in the range of 5–10 nm. The nanotubes have a diameter of 10–400 nm, and a length of up to several micrometers as evidenced by SEM. The catalytic effect of transition metals on the growth of nanotubes is noticed. The temperature-induced transformation from amorphous to crystalline structured MoS_x films results in a large lowering of the coefficient of friction under sliding against corundum in ambient air of 50% relative humidity.