Christian Mitterer

Structure of sputtered nanocomposite CrCx∕a-C:H thin films

This work presents the structural evolution of nanocomposite CrCx∕a-C:H coatings prepared by unbalanced magnetron sputtering of a metallic Cr target in Ar+CH4 glow discharges using low negative dc bias voltages. Raman spectroscopy and x-ray photoelectron spectroscopy were used to characterize the phase composition and the chemical bonding in the films deposited at different experimental conditions. The results were correlated to the chemical composition obtained by elastic recoil detection analysis. The coating microstructure was investigated on selected samples by high-resolution transmission electron microscopy combined with electron energy-loss spectroscopy analysis. The nanocomposite coatings can be divided into hard CrCx dominated films, when prepared at low CH4 partial pressure to total pressure (pt) ratios (pCH4∕pt 0.4. The structure of the low-friction a-C:H dominated coatings consists of 2–10nm sized fcc CrC crystallites ...

Thermal stability and age hardening of supersaturated AlCrN hard coatings

During advanced machining processes (high speed and dry cutting), the temperature at the cutting edge can exceed 1000uC. For modern protective hard coatings, thermal stability is of major interest. Equally important are superior mechanical properties, such as hardness, remaining at a high level over a wide temperature range. AlCrN coatings perform well in cutting tests and show excellent oxidation resistance as well as good tribological behaviour. In this work, supersaturated cubic Al0.7Cr0.3N coatings deposited by cathodic arc evaporation are studied. The phase and microstructure evolution of the material is investigated up to 1450uC using a combination of differential scanning calorimetry, thermal gravimetric analysis, mass spectrometry, X-ray diffraction and analytical transmission electron microscopy. During annealing up to 925uC, hexagonal AlN precipitates are formed at grain boundaries. At higher temperatures, a transformation of the remaining cubic AlCrN matrix into Cr via Cr2N takes place, accompanied by a release of nitrogen. After annealing up to 1450uC, the AlN grains coarsen and coalesce around the Cr and Cr2N grains. The results explain the superior cutting performance by the formation of precipitates, but also demonstrate the limitations in usage at high temperature regimes due to decomposition. Nevertheless, the substitution of Cr in the CrN lattice by Al has proven to increase the decomposition resistance significantly. Finally, nanoindentation experiments reveal that AlCrN coatings retain hardness beyond the stage of residual stress recovery up to 900uC, demonstrating an age hardening process.

Functional Thin Films for Display and Microelectronics Applications

Within the last three decades, thin films grown by physical vapor deposition methods have found widespread applications. This article reports about recent research examples on molybdenum thin films, as used for thin film transistor liquid crystal displays, and on TiN diffusion barrier films, as used for microelectronics.ZusammenfassungInnerhalb der letzten drei Jahrzehnte haben dünne mit Hilfe der physikalischen Dampfphasenabscheidung hergestellte Schichten breite Anwendung gefunden. Dieser Beitrag berichtet über jüngste Forschungsbeispiele von Molybdänschichten für Dünnschichttransistor-Flüssigkristall-Bildschirme und von TiN-Barriereschichten für die Mikroelektronik.