Characterization of α-phase aluminum oxide films deposited by filtered vacuum arc

Aluminum oxide (Al2O3) films were deposited by the filtered vacuum arc method, using a highly pure aluminum cathode and oxygen gas. Substrate temperature as high as 780°C was necessary for the formation of corundum structured α-Al2O3. Applying RF power and thus negative bias voltage to the substrate enables to increase and control the energy of substrate bombarding ions. With a negative bias voltage of 200 V, it was possible to deposit films containing α-Al2O3 with pre-heating the substrate to a temperature lower than 500°C. Increasing the voltage, thus increasing the ion energy, resulted in lowering of the critical pre-heating substrate temperature for formation of α-phase. Additionally, there was a clear difference in crystal orientation of α-Al2O3 between the films grown with and without substrate bias voltage, which was confirmed by infrared spectroscopy. Structure and phase evolution of the film were also studied by cross-sectional transmission electron microscopy.