Ulster University Logo

Ulster Institutional Repository

Comparing hardness and wear data for tetrahedral amorphous carbon and hydrogenated amorphous carbon thin films

Biomedical Sciences Research Institute Computer Science Research Institute Environmental Sciences Research Institute Nanotechnology & Advanced Materials Research Institute

Lemoine, P, Quinn, JP, Maguire, PD and McLaughlin, JAD (2004) Comparing hardness and wear data for tetrahedral amorphous carbon and hydrogenated amorphous carbon thin films. WEAR, 257 (5-6). pp. 509-522. [Journal article]

[img]PDF - Published Version
Restricted to Repository staff only

541Kb

URL: http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6V5B-4C0V853-2-2K&_cdi=5782&_user=126978&_orig=search&_coverDate=09%2F30%2F2004&_sk=997429994&view=c&wchp=dGLbVzW-zSkWz&md5=5a574bff6b0dbc7d9f354d4bf4f2fa27&ie=/sdarticle.pdf

DOI: 10.1002/j.wear.2004.01.010

Abstract

We compared nanoindentation and nanoscratch testing of 10 and 50 nm thick tetrahedral amorphous carbon (ta-C) and hydrogenated amorphous carbon (a-C:H). Raman spectroscopy shows the expected spectral features for the two carbon forms, however, luminescence from the ceramic substrate can alter the spectra. We find that hard ta-C films can blunt the diamond tip and hence use a tip area function re-calibration procedure after each indentation. This shows that, despite the correction, shallow depth hardness data is influenced by the tip geometry. Therefore, we also present a hardness slope ratio (sample/fused silica) protocol which is independent of tip geometry. The ta-C films are the hardest and the more wear resistant, i.e. for 50 nm thick ta-C films on Al2O3-TiC substrates; H (25 nm) = 51 GPa and the wear rate under a 37 GPa contact pressure is 1.8 x 10(-4) mm(3)/N in. Ramping load measurements of critical loads were complemented withscanning electron micrographs and energy dispersive X-ray (EDX) spot analysis of the wear regions. The comparison helped detect film delamination, particularly so for the thinner films. The ta-C films have higher critical loads than the a-C:H films. This finding contrasts with the large internal compressive stress usually associated with ta-C formation. In the present case, we believe that the filtered arc deposition at the floating potential provides sufficient energy for efficient atomic intermixing in the substrate but, appropriately, not enough to produce the large internal stress observed at higher energy.We note that the superior wear resistance of the ta-C films has more to do with their good adhesion to the substrate rather than their high hardness, as measured by the indenter tip. Finally, we find that a-C:H has better adhesion on silicon, whereas ta-C sticks better to theconducting ceramic substrate. (C) 2004 Elsevier B.V. All rights reserved.

Item Type:Journal article
Keywords:hardness; wear; amorphous carbon; critical load
Faculties and Schools:Faculty of Computing & Engineering
Faculty of Computing & Engineering > School of Engineering
Research Institutes and Groups:Engineering Research Institute
Engineering Research Institute > Nanotechnology & Integrated BioEngineering Centre (NIBEC)
ID Code:295
Deposited By:Mrs Ann Blair
Deposited On:19 Oct 2009 13:26
Last Modified:21 Feb 2014 14:57

Repository Staff Only: item control page