Effects of corundum-structured seeds on the low-temperature growth and hardness of the alumina-based films

The corundum-structured seeds have been introduced into alumina films using Al + α-Al₂O₃ composite and Al_100−xCr_x (x = 10, 20, 30) alloy as targets by reactive magnetron sputtering. The effects of the seeds on the elemental composition, phase composition, structure characteristic, surface morphology and nano-hardness of the alumina-based films have been investigated. The Al target has also been sputtered to prepare the alumina film as reference. The film is composed of single-phase α-Al₂O₃ by sputtering the Al + α-Al₂O₃ composite target at 550 °C, while the solid solution α-type (Al_0.7Cr_0.3)₂O₃ was detected in the film prepared with the Al₇₀Cr₃₀ target at the same temperature. The nano-hardness of the pure α-Al₂O₃ film and the α-(Al_0.7Cr_0.3)₂O₃ film were measured as ∼23.5 GPa and ∼28.5 GPa, respectively, which are much higher than that of the film deposited from Al target (∼16.3 GPa). (paper)