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

Abstract

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}more » 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.« less

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
948794
Report Number(s):
ANL/MSD/JA-58390
Journal ID: ISSN 0163-1829; PRBMDO; TRN: US200907%%249
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys. Rev. B; Journal Volume: 75; Journal Issue: 2007
Country of Publication:
United States
Language:
ENGLISH
Subject:
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

Citation Formats

Liu, A. C. Y., Arenal, R., Miller, D. J., Chen, X., Johnson, J. A., Eryilmaz, O. L., Erdemir, A., Woodford, J. B., and Cedarville Univ. Structural order in near-frictionless diamond-like carbon films probed at three length scales in the transmission electron microscope.. United States: N. p., 2007. Web. doi:10.1103/PhysRevB.75.205402.
Liu, A. C. Y., Arenal, R., Miller, D. J., Chen, X., Johnson, J. A., Eryilmaz, O. L., Erdemir, A., Woodford, J. B., & Cedarville Univ. Structural order in near-frictionless diamond-like carbon films probed at three length scales in the transmission electron microscope.. United States. doi:10.1103/PhysRevB.75.205402.
Liu, A. C. Y., Arenal, R., Miller, D. J., Chen, X., Johnson, J. A., Eryilmaz, O. L., Erdemir, A., Woodford, J. B., and Cedarville Univ. Mon . "Structural order in near-frictionless diamond-like carbon films probed at three length scales in the transmission electron microscope.". United States. doi:10.1103/PhysRevB.75.205402.
@article{osti_948794,
title = {Structural order in near-frictionless diamond-like carbon films probed at three length scales in the transmission electron microscope.},
author = {Liu, A. C. Y. and Arenal, R. and Miller, D. J. and Chen, X. and Johnson, J. A. and Eryilmaz, O. L. and Erdemir, A. and Woodford, J. B. and Cedarville Univ.},
abstractNote = {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.},
doi = {10.1103/PhysRevB.75.205402},
journal = {Phys. Rev. B},
number = 2007,
volume = 75,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Multiwavelength Raman spectroscopy has been used to study the structure of hydrogenated amorphous carbon films synthesized by plasma-enhanced chemical vapor deposition. The analysis of different parameters from the Raman spectra demonstrates that the diameter, structural, and topological orders of the sp{sup 2}-bonded ring clusters increase with increasing fractions of hydrogen in the source gas. We report the existence of an unusual peak at 867 cm{sup -1} that in such extended clusters of aromatic rings, could correspond to a graphitic mode activated by a relaxation of the phonon selection-rule resulting from defects.
  • Multiwavelength Raman spectroscopy has been used to study the structure of hydrogenated amorphous carbon films synthesized by plasma-enhanced chemical vapor deposition. The analysis of different parameters from the Raman spectra demonstrates that the diameter, structural, and topological orders of the sp{sup 2}-bonded ring clusters increase with increasing fractions of hydrogen in the source gas. We report the existence of an unusual peak at 867 cm{sup -1} that in such extended clusters of aromatic rings, could correspond to a graphitic mode activated by a relaxation of the phonon selection-rule resulting from defects.
  • In situ observation of the transformation of diamond nanoparticles (DNP) into onion-like carbon (OLC) was made during electron-beam irradiation inside an ultrahigh-vacuum transmission electron microscope at 300 kV with 8.5x10{sup 23} e/m{sup 2}. 5 nm DNP changed into OLC within about 10 min of irradiation, while 20 nm DNP did not change to OLC but to graphite. Therefore, the size effect is critical to the formation of OLC. The mechanism of formation of OLC from DNP is discussed.
  • No abstract prepared.
  • We have demonstrated that multi-wavelength Raman and photoluminescence spectroscopies are sufficient to completely characterize the structural properties of ultra-thin hydrogenated diamond-like carbon (DLC:H) films subjected to rapid thermal annealing (RTA, 1 s up to 659 °C) and to resolve the structural differences between films grown by plasma-enhanced chemical vapor deposition, facing target sputtering and filtered cathodic vacuum arc with minute variations in values of mass density, hydrogen content, and sp³ fraction. In order to distinguish unequivocally between films prepared with different density, thickness, and RTA treatment, a new method for analysis of Raman spectra was invented. This newly developed analysismore » method consisted of plotting the position of the Raman G band of carbon versus its full width at half maximum. Moreover, we studied the passivation of non-radiative recombination centers during RTA by performing measurements of the increase in photoluminescence in conjunction with the analysis of DLC:H networks simulated by molecular dynamics. The results show that dangling bond passivation is primarily a consequence of thermally-induced sp² clustering rather than hydrogen diffusion in the film.« less