The effect of process parameters on the O/Mo ratio in laser deposition of molybdenum oxides from aqueous solutions

A study on precursor concentration (0.0075–0.050M), laser power (up to 210 mW) and scanning speed (from 0.15 to 1 mm/s) dependence of chemical composition of patterns deposited by pyrolytic laser decomposition of ammonium heptamolybdate is reported. Although the deposition parameters are varied over several orders of magnitude, the chemical composition of the deposits, as determined by energy and wavelength dispersive X-ray analyses, hardly varies. On setting low-temperature processing by applying either low power or high scanning speed, the oxidation state of molybdenum in the precursor is preserved, resulting in deposition of oxides of composition near to MoO3. Using high power and low scanning speed, on the other hand, the attained higher temperatures initiate decomposition of ammonia, leading to partial reduction and yielding deposits of near-MoO2 composition.