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Title: Correlation of gas-phase composition with film properties in the plasma-enhanced chemical vapor deposition of hydrogenated amorphous carbon nitride films

Abstract

Hydrogenated amorphous carbon nitride (a-C:N:H) films were synthesized from CH{sub 4}/N{sub 2}, C{sub 2}H{sub 4}/N{sub 2}, and C{sub 2}H{sub 2}/N{sub 2} gas mixtures using inductively coupled rf plasmas. These deposition systems were characterized by means of optical emission spectroscopy and mass spectrometry (MS). The effects of varying the nitrogen partial pressure on film growth and film properties were investigated, and experimental results indicate that the hydrocarbon species produced in the gas phase contribute directly to film growth. Although the CN radical is formed in the mixed gas systems, it does not appear to be a factor in controlling the rate of film deposition. The nature and energy of the ions in these systems were explored with MS. No clear dependence of ion energy on mass or plasma conditions was observed. Although films formed in the methane and ethylene systems were relatively smooth, a-C:N:H films prepared from acetylene-nitrogen plasmas had comparatively rough surfaces, most likely as a result of the strong gas-phase polymerization process produced by the ion-molecule reactions, C{sub n}H{sub y}{sup +}+C{sub 2}H{sub 2}{yields}C{sub (n+2)}H{sub y}{sup +}+H{sub 2} (n>1, y=1-3). Correlations between the a-C:N:H growth processes and the gas-phase plasma diagnostic data are discussed.

Authors:
; ;  [1]
  1. Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872 (United States)
Publication Date:
OSTI Identifier:
20982627
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 101; Journal Issue: 2; Other Information: DOI: 10.1063/1.2424402; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ACETYLENE; AMORPHOUS STATE; CARBON NITRIDES; CHEMICAL VAPOR DEPOSITION; CRYSTAL GROWTH; EMISSION SPECTROSCOPY; ETHYLENE; HYDROGEN; ION-MOLECULE COLLISIONS; MASS; MASS SPECTROSCOPY; METHANE; MIXTURES; NITROGEN; PARTIAL PRESSURE; PHOTOLUMINESCENCE; PLASMA; POLYMERIZATION; RADICALS; THIN FILMS

Citation Formats

Liu, Dongping, Zhou, Jie, and Fisher, Ellen R. Correlation of gas-phase composition with film properties in the plasma-enhanced chemical vapor deposition of hydrogenated amorphous carbon nitride films. United States: N. p., 2007. Web. doi:10.1063/1.2424402.
Liu, Dongping, Zhou, Jie, & Fisher, Ellen R. Correlation of gas-phase composition with film properties in the plasma-enhanced chemical vapor deposition of hydrogenated amorphous carbon nitride films. United States. doi:10.1063/1.2424402.
Liu, Dongping, Zhou, Jie, and Fisher, Ellen R. Mon . "Correlation of gas-phase composition with film properties in the plasma-enhanced chemical vapor deposition of hydrogenated amorphous carbon nitride films". United States. doi:10.1063/1.2424402.
@article{osti_20982627,
title = {Correlation of gas-phase composition with film properties in the plasma-enhanced chemical vapor deposition of hydrogenated amorphous carbon nitride films},
author = {Liu, Dongping and Zhou, Jie and Fisher, Ellen R.},
abstractNote = {Hydrogenated amorphous carbon nitride (a-C:N:H) films were synthesized from CH{sub 4}/N{sub 2}, C{sub 2}H{sub 4}/N{sub 2}, and C{sub 2}H{sub 2}/N{sub 2} gas mixtures using inductively coupled rf plasmas. These deposition systems were characterized by means of optical emission spectroscopy and mass spectrometry (MS). The effects of varying the nitrogen partial pressure on film growth and film properties were investigated, and experimental results indicate that the hydrocarbon species produced in the gas phase contribute directly to film growth. Although the CN radical is formed in the mixed gas systems, it does not appear to be a factor in controlling the rate of film deposition. The nature and energy of the ions in these systems were explored with MS. No clear dependence of ion energy on mass or plasma conditions was observed. Although films formed in the methane and ethylene systems were relatively smooth, a-C:N:H films prepared from acetylene-nitrogen plasmas had comparatively rough surfaces, most likely as a result of the strong gas-phase polymerization process produced by the ion-molecule reactions, C{sub n}H{sub y}{sup +}+C{sub 2}H{sub 2}{yields}C{sub (n+2)}H{sub y}{sup +}+H{sub 2} (n>1, y=1-3). Correlations between the a-C:N:H growth processes and the gas-phase plasma diagnostic data are discussed.},
doi = {10.1063/1.2424402},
journal = {Journal of Applied Physics},
number = 2,
volume = 101,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}
  • Amorphous hydrogenated carbon nitride thin films (a-CN{sub x}:H) have been prepared by plasma-enhanced chemical vapor deposition of N{sub 2} and CH{sub 4} gases using a helical resonator discharge. The structural and optical properties of the deposited a-CN{sub x}:H films have been systematically studied as a function of the substrate temperature and radio frequency (rf) substrate bias. The chemical structure and elemental composition of the a-CN{sub x}:H films were characterized by Fourier transform infrared spectroscopy (FT-IR), x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The optical properties of the films were evaluated using transmission ultraviolet{endash}visible spectroscopy. The morphology of the films wasmore » investigated by scanning electron microscopy and atomic force microscopy. The FT-IR and XPS studies demonstrate the presence of carbon{endash}nitrogen bonds with hydrogenated components in the films. The film composition ratio N/C was found to vary from 0.127 to 0.213 depending on the deposition conditions. The Raman spectra, showing the G and D bands, indicate that the a-CN{sub x}:H films have a graphitic structure. It can be found that the optical band-gap E{sub g} of a-CN{sub x}:H films is associated with graphitic clusters, while the decrease in E{sub g} is correlated with an increase in the size and number of graphitic clusters. Combining the results of Raman and optical measurements, it can be concluded that a progressive graphitization of the films occurs with increasing the substrate temperature and rf substrate bias power, corresponding to bias voltage. {copyright} {ital 1997 American Institute of Physics.}« less
  • In this study, fullerene like carbon (FL-C) is introduced in hydrogenated amorphous carbon (a-C:H) film by employing a direct current plasma enhanced chemical vapor deposition. The film has a low friction and wear, such as 0.011 and 2.3 × 10{sup −9}mm{sup 3}/N m in the N{sub 2}, and 0.014 and 8.4 × 10{sup −8}mm{sup 3}/N m in the humid air, and high hardness and elasticity (25.8 GPa and 83.1%), to make further engineering applications in practice. It has several nanometers ordered domains consisting of less frequently cross-linked graphitic sheet stacks. We provide new evidences for understanding the reported Raman fit model involving four vibrational frequenciesmore » from five, six, and seven C-atom rings of FL-C structures, and discuss the structure evolution before or after friction according to the change in the 1200 cm{sup −1} Raman band intensity caused by five- and seven-carbon rings. Friction inevitably facilitates the transformation of carbon into FL-C nanostructures, namely, the ultra low friction comes from both such structures within the carbon film and the sliding induced at friction interface.« less
  • Nitrogen doped hydrogenated amorphous carbon thin films have been deposited by rf plasma-enhanced chemical vapor deposition using CH{sub 4} as the source of carbon and with different nitrogen flow rates (N{sub 2}/CH{sub 4} gas ratios between 0 and 3), at 300 K. The dependence modifications of the optical and the structural properties on nitrogen incorporation were investigated using different spectroscopic techniques, such as, Raman spectroscopy, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, ultraviolet-visible (UV-VIS) spectroscopy, electron spin resonance (ESR), photoluminescence (PL) and spectroscopic ellipsometry (SE). Raman spectroscopy and IR absorption reveal an increase in sp{sup 2}-bonded carbon or a changemore » in sp{sup 2} domain size with increasing nitrogen flow rate. It is found that the configuration of nitrogen atoms incorporated into an amorphous carbon network gradually changes from nitrogen atoms surrounded by three ({sigma} bonded) to two ({pi} bonded) neighboring carbons with increasing nitrogen flow rate. Tauc optical gap is reduced from 2.6 to 2.0 eV, and the ESR spin density and the peak-to-peak linewidth increase sharply with increasing nitrogen flow rate. Excellent agreement has been found between the measured SE data and modeled spectra, in which an empirical dielectric function of amorphous materials and a linear void distribution along the thickness have been assumed. The influence of nitrogen on the electronic density of states is explained based on the optical properties measured by UV-VIS and PL including nitrogen lone pair band. {copyright} 2001 American Institute of Physics.« less
  • The surface roughness and scaling behavior of a-C:H films deposited by plasma enhanced chemical vapor deposition from CH{sub 4}-Ar mixtures were studied using atomic force microscopy. Raman spectroscopy gives some insights about the film microstructure. The film surface roughness is shown to decrease with the increase of deposition negative self-bias, while the presence of Ar ions enhances this effect. An analysis of the film surface and scaling behavior suggests that there is a transition of the mechanism of the film growth from a random deposition with surface diffusion process to a thermal spike based process that occurs upon the increasemore » of the negative self-bias voltage and the argon bombardment.« less
  • The optical properties of the hydrogenated amorphous silicon carbon alloy films, prepared by plasma enhanced chemical vapor deposition technique from silane and methane gas mixture diluted in helium, have been investigated using variable angle spectroscopic ellipsometry in the photon energy range from 0.73 to 4.59 eV. Tauc-Lorentz model has been employed for the analysis of the optical spectra and it has been demonstrated that the model parameters are correlated with the carbon content as well as to the structural properties of the studied films.