Structural order in near-frictionless diamond-like carbon films probed at three length scales in the transmission electron microscope.

Journal Article · Mon Jan 01 04:00:00 EST 2007 · Phys. Rev. B

DOI:https://doi.org/10.1103/PhysRevB.75.205402· OSTI ID:948794

Liu, A C. Y.; Arenal, R; Miller, D J; Chen, X; Johnson, J A; Eryilmaz, O L; Erdemir, A; Woodford, J B

A series of hydrogenated diamondlike carbon films grown using plasma-enhanced chemical-vapor deposition is systematically studied as a function of source gas composition using transmission electron microscopy. The structure of the films is examined at three distinct length scales. Both plan-view and cross-sectional studies are undertaken to reveal any large-scale inhomogeneities or anisotropy in the films. The degree of medium-range order in the films is measured by performing fluctuation electron microscopy on the plan-view and cross-sectional specimens. Electron-energy-loss spectroscopy is employed to measure the mass density and sp{sup 2}:sp{sup 3} carbon bonding ratios of the samples. Thus, inhomogeneity as a function of depth in the film is revealed by the measurements of the short- and medium-range orders in the two different sample geometries. Soft, low-density diamondlike carbon films with low coefficients of friction are found to be more homogeneous as a function of depth in the film and possess reduced medium-range order in the surface layer. We find that these properties are promoted by employing a high hydrogen content methane and hydrogen admixture as the growth ambient. In contrast, harder, denser films with higher coefficients of friction possess a distinct surface layer with a relatively elevated level of carbon sp{sup 3} bonding and a higher degree of medium-range order. The structure of the films is examined in the light of the energetics of the growth process. It appears that a high flux of penetrating hydrogen ions modifies the surface layer containing the remnant damage from the carbon ions, homogenizing it and contributing to a lowering of the coefficient of friction.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: SC
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 948794
• Report Number(s): ANL/MSD/JA-58390
• Journal Information: Phys. Rev. B, Journal Name: Phys. Rev. B Journal Issue: 2007 Vol. 75; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

03 NATURAL GAS
08 HYDROGEN
ANISOTROPY
BONDING
CARBON
CARBON IONS
DEPOSITION
ELECTRON MICROSCOPES
ELECTRON MICROSCOPY
FLUCTUATIONS
FRICTION
HYDROGEN
HYDROGEN IONS
METHANE
SPECTROSCOPY
TRANSMISSION ELECTRON MICROSCOPY