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Title: Growth mechanism and composition of ultrasmooth a-C:H:Si films grown from energetic ions for superlubricity

Abstract

Growth mechanism and ion energy dependence of composition of ultrasmooth a-C:H:Si films grown from ionization of tetramethylsilane (TMS) and toluene mixture at a fixed gas ratio have been investigated by varying the applied bias voltage. The dynamic scaling theory is employed to evaluate the roughness evolution of a-C:H:Si films, and to extract roughness and growth exponents of α ∼ 0.51 and β ∼ 0, respectively. The atomically smooth surface of a-C:H:Si films with Ra ∼ 0.1 nm is thermally activated by the energetic ion-impact induced subsurface “polishing” process for ion dominated deposition. The ion energy (bias voltage) plays a paramount role in determining the hydrogen incorporation, bonding structure and final stoichiometry of a-C:H:Si films. The hydrogen content in the films measured by ERDA gradually decreases from 36.7 to 17.3 at. % with increasing the bias voltage from 0.25 to 3.5 kV, while the carbon content in the films increases correspondingly from 52.5 to 70.1 at. %. The Si content is kept almost constant at ∼9–10 at. %. Depending on the ion-surface interactions, the bonding structure of a-C:H:Si films grown in different ion energy regions evolves from chain-developed polymer-like to cross-linked diamond-like to sp{sup 2}-bonded a–C as revealed by XPS, Raman, and FTIR analysis. Such a structural evolution ismore » reflected in their measured nanomechanical properties such as hardness, modulus, and compressive stress. An enhanced viscoplastic behavior (i.e., viscoplastic exponent of ∼0.06) is observed for polymeric a-C:H:Si films. A hydrogen content threshold (H > 20 at. %) exists for the as-grown a-C:H:Si films to exhibit superlow friction in dry N{sub 2} atmosphere. An extremely low friction coefficient of ∼0.001 can be obtained for polymer-like a-C:H:Si film. These near-frictionless a-C:H:Si films are strongly promising for applications in industrial lubricating systems.« less

Authors:
;  [1]
  1. Department of Mechanical Engineering, The University of Tokyo, Tokyo 113-8656 (Japan)
Publication Date:
OSTI Identifier:
22275634
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 115; Journal Issue: 4; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CRYSTAL GROWTH; DEPOSITION; DIAMONDS; ELECTRIC POTENTIAL; ENERGY DEPENDENCE; FOURIER TRANSFORMATION; FRICTION FACTOR; HARDNESS; HYDROGEN; INFRARED SPECTRA; POLYMERS; RAMAN SPECTROSCOPY; ROUGHNESS; SILICON; TAIL IONS; THIN FILMS; TOLUENE; X-RAY PHOTOELECTRON SPECTROSCOPY

Citation Formats

Chen, Xinchun, and Kato, Takahisa. Growth mechanism and composition of ultrasmooth a-C:H:Si films grown from energetic ions for superlubricity. United States: N. p., 2014. Web. doi:10.1063/1.4863123.
Chen, Xinchun, & Kato, Takahisa. Growth mechanism and composition of ultrasmooth a-C:H:Si films grown from energetic ions for superlubricity. United States. https://doi.org/10.1063/1.4863123
Chen, Xinchun, and Kato, Takahisa. 2014. "Growth mechanism and composition of ultrasmooth a-C:H:Si films grown from energetic ions for superlubricity". United States. https://doi.org/10.1063/1.4863123.
@article{osti_22275634,
title = {Growth mechanism and composition of ultrasmooth a-C:H:Si films grown from energetic ions for superlubricity},
author = {Chen, Xinchun and Kato, Takahisa},
abstractNote = {Growth mechanism and ion energy dependence of composition of ultrasmooth a-C:H:Si films grown from ionization of tetramethylsilane (TMS) and toluene mixture at a fixed gas ratio have been investigated by varying the applied bias voltage. The dynamic scaling theory is employed to evaluate the roughness evolution of a-C:H:Si films, and to extract roughness and growth exponents of α ∼ 0.51 and β ∼ 0, respectively. The atomically smooth surface of a-C:H:Si films with Ra ∼ 0.1 nm is thermally activated by the energetic ion-impact induced subsurface “polishing” process for ion dominated deposition. The ion energy (bias voltage) plays a paramount role in determining the hydrogen incorporation, bonding structure and final stoichiometry of a-C:H:Si films. The hydrogen content in the films measured by ERDA gradually decreases from 36.7 to 17.3 at. % with increasing the bias voltage from 0.25 to 3.5 kV, while the carbon content in the films increases correspondingly from 52.5 to 70.1 at. %. The Si content is kept almost constant at ∼9–10 at. %. Depending on the ion-surface interactions, the bonding structure of a-C:H:Si films grown in different ion energy regions evolves from chain-developed polymer-like to cross-linked diamond-like to sp{sup 2}-bonded a–C as revealed by XPS, Raman, and FTIR analysis. Such a structural evolution is reflected in their measured nanomechanical properties such as hardness, modulus, and compressive stress. An enhanced viscoplastic behavior (i.e., viscoplastic exponent of ∼0.06) is observed for polymeric a-C:H:Si films. A hydrogen content threshold (H > 20 at. %) exists for the as-grown a-C:H:Si films to exhibit superlow friction in dry N{sub 2} atmosphere. An extremely low friction coefficient of ∼0.001 can be obtained for polymer-like a-C:H:Si film. These near-frictionless a-C:H:Si films are strongly promising for applications in industrial lubricating systems.},
doi = {10.1063/1.4863123},
url = {https://www.osti.gov/biblio/22275634}, journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 4,
volume = 115,
place = {United States},
year = {Tue Jan 28 00:00:00 EST 2014},
month = {Tue Jan 28 00:00:00 EST 2014}
}