A comparative study of Cr2O3 thin films obtained by MOCVD using three different precursors

Thin films of chromia (Cr2O3) for anti-wear protection were grown by metal-organic (MO)CVD on AISI 304 stainless steel, soda-lime glass, and (001) silicon substrates. The structural, morphological, and chemical compositions were compared for films grown by using three different, commercial, organochromium compounds; Cr(CO)6 (1), Cr(III) (hexafluoroacetylacetonate) (2), and tris(2,2,6,6-tetra-methyl-3,5-heptanedionato) chromium (III) (3). The depositions were performed using a hot-wall reactor at 500 °C, under 3 torr, using N2 as the carrier gas and O2 mixed with water vapor as the reactant gas. The films were analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM), Rutherford backscattering (RBS), nuclear reaction analysis (NRA), elastic recoil detection (ERD), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared (FTIR) spectroscopy. The films grown with all three precursors on all three substrates were crystalline with hexagonal Cr2O3 eskalonite structure. FTIR and XPS measurements confirmed the XRD results, showing IR absorption bands characteristic of Cr2O3 and an oxidation state +3 of chromium. The highest growth rate was obtained with precursor (1) (20 nm min-1). Films grown with (1) on stainless steel were analyzed by nanoindentation measurements and scratch test to determine the hardness and the film adhesion.