Vanadium oxicarbide thin films prepared by conventional chemical vapor deposition from vanadyl acetylacetonate

Vanadium oxicarbide thin films were prepared by conventional atmospheric-pressure chemical vapor deposition. The precursor was vanadyl acetylacetonate and substrates were high alloyed steel and stainless steel. A reducing atmosphere of H-2 was used and heating was performed at a rate of 40 degrees C/min with two isotherms. The first one lasted 1 h at 500 degrees C and the second varied in time from 1 h to 2 h at 1000 degrees C. The thickness measurements were made by a calotest (ball crater test). During the first isotherm, surface activation and nucleation of the deposit apparently occurred, with the formation of a non-homogeneous amorphous layer containing V2O5 and free carbon, as shown by X-ray photoelectron spectroscopy (XPS). Further increments modified the structure to oxicarbide as major phase. 1% CH4 addition to the reactive gas at 1000 degrees C considerably improved the adhesion of coating to substrate. Scanning electron microscopy (SEM) and XPS showed that oxygen concentration in the coating was reduced by increasing the duration of the second isotherm at the same reducing capacity of the reactive gas. (C) 1997 Elsevier Science S.A.