Intrinsic Residual Stress Induced by the Ion Bombardment in Dense T-Zone Cr Thin Films

For energetic deposition, ion bombardment is an important factor independent of grain size for influencing the residual stress, and the energy and flux are critical parameters to determine the residual stress evolution. In this work, modulated pulsed power magnetron sputtering ( MPPMS) and deep oscillation magnetron sputtering (DOMS) were employed to control the energy and flux to modulate the ion bombardment for intrinsic stress generation under similar average power. The films thickness was selected at 0.1, 0.2, 0.5, 1.0, 1.5 and 3.0 mu m to give a comparative study of the intrinsic part of residual stress. All Cr coatings were textured along Cr(110) preferred orientation with dense T-zone columnar microstructure of equivalent grain size. Compared with MPPMS, Cr thin films deposited by DOMS show a compressive residual stress tendency. When the thickness of Cr thin films is under 0.5 mu m, Cr thin films deposited by DOMS show higher compressive residual stress. Further increasing the film thickness, the compressive residual stress first shows a sudden decrease in a sharp slope, and then turns to relative slow decrease and gradually turns to show tensile stress. In the film continuous growing process, the ion bombardment shows limited effect in the early growth stage, but energy of the bombardment ions shows obvious effect on residual stress when the thin film grows thicker. Ion energy is an important factor influencing the formation of compressive residual stress, and ion bombardment with high energy assists the generation and control of compressive residual stress.