Synthesis of a-Al2O3 thin films using reactive high-power impulse magnetron sputtering

alpha-alumina coatings have been deposited directly onto cemented-carbide and Mo substrates at a temperature as low as 650 deg C using reactive high-power impulse magnetron sputtering (HiPIMS) of Al in an Ar/02 gas mixture. The coatings consisted of plate-like crystallites, as revealed by scanning electron microscopy. a phase growth was retained over the studied range of substrate bias voltages (from floating potential up to -100 V), with films exhibiting a slightly denser microstructure at higher bias voltages. X-ray diffraction indicated that the a-alumina grains had a preferred orientation of (0001)-planes perpendicular to the substrate surface. X-ray analysis of films deposited at 575 deg C indicated the presence of 7-alumina, whereas films grown at 500 deg C or lower were X-ray amorphous.