Growth of α-(Al,Cr)2O3
Thin Films by Reactive r.f. Magnetron Sputtering
D. Diechle, M.
Stüber, H. Leiste (Harald.Leiste@imf.fzk.de),
S. Ulrich, Forschungszentrum Karlsruhe, Germany, V. Schier, Walter AG,
The 36th International Conference on Metallurgical
Coatings and Thin Films,
Posterpräsentation, Hard Coatings
and Vapor Deposition Technology, Symposium B Poster Session30.04.2009
Advanced thin film materials for cutting tool applications require complex
roperty profiles including high hardness, toughness,
wear and corrosion resistance. Such materials are expected for example in the
Al-Cr-O system. The materials science approach behind this work is to quench
Al-Cr-O thin film materials in a metastable
corundum-type solid solution structure directly from the vapor phase at
deposition temperatures significantly below the temperature range of the
thermodynamic stable phase which exists only above 1300°C in the corresponding
Al-Cr-O phase diagram. First, we will describe a combinatorial approach using a
segmented target consisting of aluminum and chromium plates for the deposition
of Al-Cr-O thin films by reactive r.f. magnetron
sputtering. This experimental procedure results in the growth of coatings of different
composition and microstructure in dependence of the sample positions in
relation to the target. For specific deposition conditions stoichiometric,
nanocrystalline solid solution strengthened
(Al1-x,Crx)2O3 thin films were grown in a corundum-type structure. Secondly, we
derive from these experiments fixed individual material compositions and use
homogeneous metallic targets with an appropriate Al:Cr
composition for reactive r.f. magnetron sputtering. Similar
coatings grown by these different approaches will be compared with respect to
their constitution, microstructure and properties. The deposition experiments
are carried out with a Leybold Z 550 PVD machine in
an argon–oxygen plasma. The cathode power is set to 500 W in r.f. mode, and the total gas pressure is 0.65 Pa in all
experiments. During deposition the substrate temperature is controlled in the
range from 180°C to 600°C. In addition, a substrate bias up to -400 V is
induced with a second r.f. power supply. Commercial
cemented carbide substrates and silicon wafers are coated. The coatings are
characterized by determining their thickness, Vickers micro hardness, residual
stress, density, chemical composition, constitution (by XRD) and their
microstructure (by REM and TEM).