Combined surface characterization and tribological (friction and wear) studies of CVD diamond films
- Department of Chemistry, University of California, Berkeley, California 94720 (United States)
- Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States)
The tribological properties of polycrystalline chemically vapor deposited (CVD) diamond films grown on silicon substrates and containing varying amounts of amorphous carbon impurities were investigated. Films were characterized by secondary electron microscopy (SEM) and atomic force microscopy (AFM) for surface morphology and roughness and by spatially resolved Raman spectroscopy for amorphous carbon ([ital a]-C) content. Friction measurements were performed with a Rockwell C hemispherical diamond tip in ultrahigh vacuum (UHV) and in ambient air. In vacuum, the friction coefficient rises monotonically from 0.6 in a region with substantial [ital a]-C to 0.85 in a region with pure diamond. Under ambient conditions, the friction coefficient is substantially lower than that in vacuum and decreases slightly (from [similar to]0.19 to [similar to]0.16) with the decreasing [ital a]-C content. Under both vacuum and ambient conditions, the friction coefficient was observed to be independent of load over the range of 0.1--0.5 N. The friction values are discussed in terms of adhesion between the diamond tip and the film. Qualitative scratch hardness measurements were performed in UHV by measuring the minimum load at which plastic deformation occurs for a single traversal of the tip. Scratch hardness is found to increase with increasing diamond content of the films. The wear mechanism of the pure diamond regions was evaluated by examining wear tracks with SEM and AFM. The weak tracks showed evidence of spalling, buckling, and grain pull-out indicative of a cohesive mode of failure (failure at grain boundaries). A decrease in surface roughness in the wear tracks indicates asperity wear. Adhesive failure at the Si substrate interface or of a phase transformation of the diamond film was not observed in this load regime.
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5906283
- Journal Information:
- Journal of Materials Research; (United States), Vol. 8:10; ISSN 0884-2914
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
DIAMONDS
CHEMICAL VAPOR DEPOSITION
TRIBOLOGY
AMORPHOUS STATE
CARBON
FILMS
IMPURITIES
MICROSCOPY
POLYCRYSTALS
RAMAN SPECTRA
SILICON
SUBSTRATES
ULTRAHIGH VACUUM
CHEMICAL COATING
CRYSTALS
DEPOSITION
ELEMENTAL MINERALS
ELEMENTS
MINERALS
NONMETALS
SEMIMETALS
SPECTRA
SURFACE COATING
360603* - Materials- Properties