Effect of heat treatment on mechanical property of amorphous carbon films by magnetron sputtering

Abstract

To investigate the effects of heat treatment methods and processes on the mechanical properties of amorphous carbon (a-C) films prepared using magnetron sputtering, the microstructures and mechanical properties of a-C films were characterized using X-ray photoelectron spectroscopy, nanoindentation testing, and ball disk friction testing. Results show that heat treatment helps to improve the mechanical properties of a-C films. The mechanical properties of a-C films are affected not only by the hybrid of SP2 and SP3 in the microstructure but also by their surface morphologies and the form of interface bonding between amorphous carbon films and silicon substrates after heat treatment. The hardness of the a-C films increased by 35.15 % upon treatment at the optimal temperature of 900 °C. The heat treatment also increased the Young's modulus of the films. Moreover, the heat treatment improved the wear resistance of the treated films with an optimal temperature of 1000 °C. The wear area is also reduced by 28 % compared with that before heat treatment. At 1200 °C, the wear resistance of a-C film decreased owing to the reduction in the SP2 carbon hybrid structure, and the wear mechanism of a-C films after heat treatment changed from mixed damage (abrasive and adhesive wears combined) to simple abrasive damage. All these results indicated the proposed magnetron sputtering heat treatment is an effective way to improve mechanical properties of a-C films. At the same time, the heat treatment also improved the interfacial adhesion between the amorphous carbon film and silicon wafer. Moreover, the interfacial adhesion between the amorphous carbon film and silicon wafer reached grade 5 when the heat treatment temperature exceeded 1000 °C.