MoSx thin films by thermolysis of a single-source precursor

Thin films of MoSx have been prepared on silicon substrates by spin coating and thermolysis of 0.5 M solutions of alkyldiammonium tetrathiomolybdates in 1,2-ethanediamine (EDA) and 1,2-propanediamine (12PDA). The films have been heat treated in air at temperatures between 80 and 250 degreesC and under N-2 atmosphere at temperatures between 300 and 800 degreesC. X-ray diffraction shows a restricted crystallisation and amorphous residues in both kind of films. EDA-based films exhibit a high tendency to crystallise whereas 12PDA-based films form associated structures with the solvent preventing precursor crystallisation. An insight into the processes occurring in film formation is gained by infrared spectroscopy which indicates a beginning of the decomposition of the 12PDA-based film at temperatures as low as 80 degreesC with incorporation of the diamine solvent. In contrast, the EDA-based films show first signs of a decomposition at 150 degreesC. The decomposition of the intermediate MoS3 in both cases starts between 250 and 300 degreesC. By means of SNMS depth profiles carbon contents up to 21 and 32 atom-% were found in EDA- and 12PDA-based films, respectively. The films show a significant deficit of sulphur which is compensated by the carbon. Near the surface of the coatings a loss of carbon is observed.