Elsevier

Thin Solid Films

Volume 709, 1 September 2020, 138188
Thin Solid Films

Influence of nitrogen doping on the thermal stability of hydrogenated amorphous diamond coating

https://doi.org/10.1016/j.tsf.2020.138188Get rights and content

Highlights

  • The a-C:H:N includes Csp3 and Nsp3, which reaches maximum at 0.12 at.% n.

  • N promotes Nsp3, C = N and CHn bond formation in the a-C:H:N.

  • The annealed a-C:H:N can hold high hardness.

Abstract

The nitrogen-doped hydrogenated diamond like coatings (a-C:H:N) with 0–3 at.% nitrogen content were deposited onto 316 L steel substrate by PECVD. The x-ray photoelectron spectroscope, Raman spectroscopy, and Fourier transformation infrared spectroscopy are used to study their bonding structure evolution during annealing. Effect of annealing on their hardness and residual stress is also evaluated by nano indenter and film stress instrument. It shows that the sp3 fraction in a-C:H:N coatings contains lot of Nsp3 and reaches the maximum around 0.12 at.% N content. The a-C:H:N coating with 2.95 at.% N can keep high sp3 fraction and high hardness 12.4 GPa even after annealed at 590 °C.

Introduction

Because of their amorphous structure mixing sp2 and sp3 hybrid carbon atoms, diamond-like coatings (DLCs) present excellent physical and chemical properties and offer potential as advanced materials applied extensively in mechanical engineering, biomedicine, and aeronautical or aerospace fields [1,2]. However, the intrinsic high residual stress, weak adhesion strength, and nonideal thermal stability of DLCs are their key drawbacks in practical applications. The thermal stability of DLCs is mainly related to graphitization process at elevated temperature, in which sp3 C transforms to sp2 C due to bond breakage and atomic rearrangement [3], [4], [5], [6], [7]]. Graphitization not only affects the practical performance of DLCs [8,9], but also changes their size stability induced by volume expansion of the coating [10].

Nitrogen doping in DLCs is beneficial for leading to release of intrinsic residual stress, improving adhesion strength and wear resistance, and the surface modification of coatings [11], [12], [13], [14], [15], although it degrades the surface hardness when the nitrogen content is higher [16,17]. There are much argument about the effect of nitrogen doping on the thermal stability of DLCs. Carbon atoms preferentially bond with N atom to depress Csingle bondH bonds in the coating [18], even form extremely strong Csingle bondN valence bonds to improve the thermal stability of DLCs [19], [20], [21]. On the other hand, the doping nitrogen in DLCs can enhance sp2 C fraction, even promote the transformation of C = N to C = C bonds during annealing to intensify the graphite clustering and graphitization [22,23]. Thus, the so called “better thermal stability of DLCs containing nitrogen” is probably related to its high sp2 fraction in the as-deposited coatings.

Whether the DLC is hydrogenated or not, a few reports concern that sp3 fraction of as-deposited coating is reinforced by the doping N under low nitrogen content [24]. It is not surprising because the fraction of sp3 and sp2 of Csingle bondC bonds and Csingle bondN bonds is controlled by fabrication processing, especially the bonding environment and inputting ion energy [25,26]. But the mechanism for this sp3C “abnormally” rising with nitrogen addition is unknown up to now, and there is little study on the thermal stability of this kind of N-doped DLCs. Recently we also find that nitrogen doping can enhance the sp3 fraction under some specific processing condition. Thus, it is necessary to investigate the mechanism behind these test results.

In this study, the nitrogen content of a-C:H:N coatings was limited to the 0–3 at% range by controlling the nitrogen gas flow, and their structure, nanohardness, and residual stress evolution during annealing were investigated. The results presented should provide some ideas on fabricating a-C:H:N coatings with combined excellent properties of high hardness, low intrinsic residual stress, and high thermal stability.

Section snippets

Experimental procedure

The a-C:H:N coatings were deposited onto 316 L stainless steel and silicon wafer substrate coupons by means of a Hauzer Flexicoat 850 PECVD system. First, the polished specimen were cleaned in a ultrasonic ethanol bath and dried by nitrogen gas flow. Then the specimen were introduced into the vacuum chamber, which was then pumped to <5 × 10−3 Pa. The specimens were then argon ion etched by a hot filament ion source for 90 min, during which the current was 100 A, the Ar gas (99.999% pure) flow

Raman spectra characterization

The Raman spectra of DLCs typically exhibit two feature peaks, i.e., at wavenumbers of 1580 and 1350 cm−1 for the G and D peaks, respectively, which include much information about hybridization bond fraction, carbon clustering, disorder, and so on. The G peak comes from the stretching vibration of C sp2 of either the ring or chain, and the D peak reflects vibration induced by structure disorder, and it is mainly related to the aromatic ring in DLCs [[1], [2], [3], [4], [5],29,30]. Under certain

Conclusions

The a-C:H:N coatings with high sp3 fraction and 0–3 at.% nitrogen content were prepared by PECVD, in which the total sp3 includes Nsp3 and Csp3. In this study, the doping N enhances sp3 fraction till around 0.12 at.% N in the as-deposited coating. When more nitrogen is added, extra nitrogen dominantly forms C = N bonds in the coating. Thus a-C:H:N coatings with low nitrogen constitute a spacious structure with dense and distorted sp3 network frame, dense and small graphite clusters pinned by C

CRediT authorship contribution statement

Jihua Peng: Supervision, Methodology, Supervision, Conceptualization, Methodology, Writing - review & editing. Manzhong Yang: Investigation, Data curation, Writing - original draft, Writing - original draft, Data curation, Investigation, Validation. Jiwei Zeng: . Dongyi Su: . Jingwen Liao: Investigation. Man-lung Yick: .

Declaration of Competing Interest

None.

Acknowledgments

This work was supported by the Science and Technology Program of Guangzhou City (Grant Nos. 201902010018, 201807010091, and 2017010160670) and the Science and Technology Program of Guangdong Province (Grant No. 2015B090923006).

Reference (52)

  • S. Ray et al.

    P. Papakonstantinou, Iron, nitrogen and silicon doped diamond like carbon (DLC) thin films: a comparative study

    Thin Solid Films

    (2016)
  • W. Kulisch et al.

    Investigation of the thermal stability of nitrogen-rich amorphous carbon nitride films

    Thin Solid Films

    (2000)
  • Y. Zou et al.

    Mechanical properties and thermal stability of nitrogen incorporated diamond-like carbon films

    Vacuum

    (2009)
  • Z. Zhou et al.

    The investigation of carbon nitride films annealed at different temperatures

    Appl. Surf. Sci

    (2003)
  • W. Zhang et al.

    Raman analysis of laser annealed nitrogen doped amorphous carbon film

    Solid State Commun

    (2002)
  • N. Dwivedi et al.

    Influence of bonding environment on nano-mechanical properties of nitrogen containing hydrogenated amorphous carbon thin films

    Mater. Chem. Phys.

    (2011)
  • R. Sheng et al.

    Effect of unbonded hydrogen on amorphous carbon film deposited by PECVD with annealing treatment

    Diamond Relat. Mater

    (2018)
  • S. Shiri et al.

    Evaluation of Stoney equation for determining the internal stress of DLC thin films using an optical profiler

    Surf. Coat. Technol

    (2016)
  • Y. Lin et al.

    Annealing effect on the structural, mechanical and electrical properties of titanium-doped diamond-like carbon films

    Thin Solid Films

    (2009)
  • Z. Seker et al.

    The effect of nitrogen incorporation in DLC films deposited by ECR microwave plasma CVD,t Appl

    Surf. Sci.

    (2014)
  • X. Yan et al.

    Study of structure, tribological properties and growth mechanism of DLC and nitrogen-doped DLC films deposited by electrochemical technique

    Appl. Surf. Sci

    (2004)
  • M. Ahmed et al.

    Comparison between FTIR and XPS characterization of amino acid glycine adsorption onto diamond-like carbon (DLC) and silicon doped DLC

    Appl. Surf. Sci

    (2013)
  • R.D. Noce et al.

    The influence of residual stress and crystallite size on the magnetic properties of electrodeposited nanocrystalline Pd-Co alloys

    Surf. Coat. Technol

    (2007)
  • G. Liu et al.

    Effects of substrate temperature on the structure, residual stress and nanohardness of Ti6Al4V films prepared by magnetron sputtering

    Appl. Surf. Sci

    (2016)
  • D. Debajyoti et al.

    Anti-reflection coatings for silicon solar cells from hydrogenated diamond like carbon

    Appl. Surf. Sci

    (2015)
  • U. Irfan et al.

    The performance of DLC-coated and uncoated ultra-fine carbide tools in micromilling of Inconel 718

    Precision Eng

    (2015)
  • Cited by (9)

    • Friction and wear performance of hydrogenated diamond-like coatings with non-metal element complex dopants against alumina in ambient air

      2023, Wear
      Citation Excerpt :

      This indicates that the sp3C faction and sp2C clustering sizes can be tuned by the addition of dopants. Si/O binary doping can increase the sp3C fraction significantly [10], and single N doping can maintain almost the same sp3C fraction as pure a-C:H films [14,29]. Si/O/N tertiary doping decreases the sp3C fraction greatly, but sp2C clustering can be clearly ordered [37].

    • Investigating the effect of bias voltage on the microstructural thermal stability and tribological performance of N-doped hydrogenated diamond-like carbon coatings

      2022, Surface and Coatings Technology
      Citation Excerpt :

      The more energic the impinging C+ particle is, the more severe the bond structure distortion that induces a larger residual stress in the coating. Sample B# had the highest sp3C fraction, the highest surface hardness, and a lower residual stress, likely owing to the deposition environment in this study, which was conducive to improving adhesion [24,45]. Therefore, this coating exhibited the best wear resistance when the abrasive and adhesive modes dominated during the sliding friction.

    • Effect of nitrogen doping on the microstructure and thermal stability of diamond-like carbon coatings containing silicon and oxygen

      2021, Surface and Coatings Technology
      Citation Excerpt :

      Moreover, the addition of N2 to the working gas reduced the O content in the as-deposited coating. This accounts for the following factors: 1) the dissociation capacity difference of the gas sources [31] and 2) enhancement of surface ion etching from N+ [23,32]. This is probably because of the low dissociation rate of N2, as well as the fact that the N2 inlet was close to the pump location.

    View all citing articles on Scopus
    View full text