Influence of bias voltage on the microstructure and physical properties of magnetron sputtered Zr-Si-N nanocomposite thin films

We report an investigation concerning the influence of ion bombardment on the nanostructure and physical properties of Zr-Si-N nanocomposite thin films. The films were deposited by reactive magnetron sputtering from individual Zr and Si targets. The Si content was varied by changing the power applied to the Si target. The increase of ion bombardment energy was obtained by applying a negative potential U-b = -150 V to the substrate. The evolution of the film texture. grain size and lattice constant was mapped out using X-ray diffraction measurements. Zr-Si-N films deposited at a substrate temperature T-s = 510 K with a bias voltage of U-b (=) -150 V exhibit less pronounced columnar structure with small crystallites having various orientations. The maximum nanohardness of 39 GPa is reached for the films at about 2.5 at.% Si, 8 nm grain size and 0.3 Si surface coverage. The increased energy of ionic species reaching the substrate when a negative bias voltage is applied seems to have the opposite effect to that of increasing substrate temperature: reduced SiNx coverage on the ZrN nanocrystallites. (C) 2009 Elsevier B.V. All rights reserved.