SYNTHESIS AND CHARACTERIZATION OF TUNGSTEN DISULFIDE FILMS GROWN BY PULSED-LASER DEPOSITION

The synthesis and characterization of tungsten disulphide (WS2) films grown on 440C stainless steel substrates using the 248 nm line from a KrF excimer laser are reported. Film properties could be adjusted by c ontrolling substrate temperature and by laser or thermal anneals. X-ra y photoelectron spectroscopy, glancing angle XRD, Raman spectroscopy a nd high-resolution scanning electron microscopy were used to evaluate film chemistry, crystallinity and morphology. Films grown at room temp erature were amorphous, near stoichiometric, and had a multiplicity of chemical states. Local order and bonding were improved most dramatica lly through post-deposition laser anneals. Crystallite size could be i ncreased by raising the substrate temperature during deposition and, t o a lesser degree, by post-deposition thermal anneals. Local disorder was observed within the larger crystallites compared to those that wer e laser annealed. Crystallinity was induced in amorphous films by mech anical rubbing at room temperature under conditions where frictional h eating was negligible. The degree of control over film properties prov ided by PLD demonstrates its value for growing/designing tribological coatings.