Mechanical properties of a-C : H multilayer films

Multilayered amorphous hydrogenated carbon (a-C:H) films consisting of alte rnating sublayers with different mechanical properties have been deposited by an electron cyclotron resonance microwave-plasma chemical vapor depositi on (ECR MP-CVD) system and modulating substrate bias voltage. The mechanica l properties of the multilayer films were determined using nanoindentation and nanoscratch experiments with reference to single a-C:H layers of which the multilayer structure were composed. In nanoindentation tests, the relat ionship between the film hardness and indentation depth has been obtained o ver an indentation depth range of 20-500 nm. Since the films tend to fractu re under high load in nanoindentation tests, their critical fracture loads were determined. The critical loads for fracturing the multilayered a-C:H f ilms were higher than those of single a-C:H layers. The nanoscratch tests a lso showed that the multilayered a-C:H films required a higher critical loa d for scratching fracture. This study implies that the mechanical propertie s of a-C:H film can be improved by engineering suitable multilayer structur es. (C) 2001 Elsevier Science B.V. All rights reserved.