Synthesis of low oxygen concentration molybdenum nitride films

Abstract

Polycrystalline, small grain size, 15 μm thick Mo x N ( x=1 and 2) films containing ≈60 at.% γ-Mo 2N and ≈40 at.% δ-MoN and void of Auger detectable concentrations of molybdenum oxides, have been prepared on 50-μm thick nitrided Ti substrates via programmed reaction and subsequent anneal at 750°C for 2 h of the precursor MoO 3 films with NH 3. The latter films were prepared via liquid spray pyrolysis of an MoCl 5/methanol mixture in air at 500°C. By contrast, residual MoO 2 occurred near the film–substrate interface in Mo x N films produced using the same programmed reaction but where MoO 3 had been deposited on bare Ti substrates. The change in density of MoO 3 ( ρ=4.69 g cm −3) to γ-Mo 2N ( ρ=9.50 g cm −3) and δ-MoN ( ρ=9.05 g cm −3), as well as the nature of the topotactic conversion, produced grains which had a calculated average size of 10 nm and which exhibited good adhesion to the substrate. Variations in the conversion heating rates and the NH 3 flow rates also affected both the phase composition and the average grain size of the intermediate and the final reaction products. Scanning electron microscopy (SEM) of the Mo x N films revealed a highly porous surface morphology.