Composition and microstructure of r.f. magnetron sputter-deposited Cr-Zr-O thin films

Stefanie Spitz, Michael Stüber, Harald Leiste, Sven Ulrich

Karlsruhe Institute of Technology (KIT), Institute for Applied Materials (IAM-AWP), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

Cr-Zr-O thin films were synthesised by reactive r.f. magnetron sputtering in an argon-oxygen atmosphere at a pressure of 0.4 Pa. While keeping the substrate temperature constant at 500 °C, the r.f. substrate bias was systematically varied between 0 V and -200 V to investigate the effect of ion bombardment during film growth on microstructure and phase formation. Following a combinatorial approach for thin film deposition by using a segmented Cr-Zr-sputter-target, thin films of five different elemental compositions from Cr-rich to Zr-rich could be obtained in one deposition process.

The evolution of the microstructure and phase formation has been studied by X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). In addition, a Rietveld simulation was done on selected films. The elemental composition of the films was analysed by Electron Probe Micro-Analysis (EPMA).

XRD reveals nanocrystalline microstructures for all films. It is shown that at low substrate bias and high Cr content thin films with a corundum structure are obtained. With increasing substrate bias and increasing Zr content ZrO₂ like structures are observed, even the high temperature cubic and tetragonal phases.