Atomic constraint in hydrogenated ‘‘diamond-like’’ carbon

Tamor, M. A.; Vassell, W. C.; Carduner, Keith R.

doi:10.1063/1.104597

Cited by 245 publications

(83 citation statements)

References 12 publications

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“…For the films produced in this work, this combination is in agreement with a-C:H in the literature because of a non-extreme values founded that reveal good hardness (10 < H < 20 GPa), and good low friction coefficients at the same time. It's consistent when we confirm sp 2 and sp 3 sites for those films, characterizing the status of a-C:H films as observed by Tamor et al (39) to derive the fractions of the various C-H configurations. In our case, aromatic rings formed in the C films are resistant against penetration, explaining the good hardness properties.…”

Section: Hardnesssupporting

confidence: 70%

Study of a-C:H thin films grown by PIII in different times for Mechanical and Tribological applications

SantAna¹,

Santos²,

Silva³

et al. 2017

RBAV

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A Steel alloy (16MnCr5) used for automotive applications (engine components) was chosen as substrate to be covered by DLC films deposited by Plasma Immersion Ion Implantation. This kind of recovery is useful for improve its mechanical and tribological applications, more specific to increase surface hardness and to reduce the friction coefficient (µ). After polished and ultrasonicated, 16MnCr5 substrates were submitted to PIIID procedures for 100 W of radiofrequency power, from atmospheres supplied with 80% of methane and 20% of argon, keeping the work pressure fixed to 5.5 Pascal. Four different deposition times was chosen being of (1800 s, 3600 s, 5400 s and 7200 s). PIII parameters were (-3600 V, 30 µs and 300 Hz). It was investigated the effect of DLC properties over the substrates using Raman Spectroscopy (for Hydrogen content and microstructure analysis), Ultra Micro-Tribometer (for friction coefficient: µ) and Nanoindentation (hardness).

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Section: Hardnesssupporting

confidence: 70%

Study of a-C:H thin films grown by PIII in different times for Mechanical and Tribological applications

SantAna¹,

Santos²,

Silva³

et al. 2017

RBAV

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“…We suggest that the answer is that the unresolved hydrogen hyperfine interactions make an increasingly large contribution as the ion energy is reduced. a-C:H deposited by the usual PECVD process has a hydrogen content which increases as the bias voltage is decreased 11,36 and the increase is most rapid for V b Ͻ100 V. 36 For our samples it is estimated to increase from 13 at. % at 100 V to about 50%, typical of polymerlike a-C:H, at about 10 V. Unresolved hyperfine lines are expected to give rise to a Gaussian line shape with an overall full width at half height given by 24…”

Section: Analysis Of Linewidth Variation For V B ë100 V: Dipolar Amentioning

confidence: 99%

“…This is plausible since we have seen that the unpaired spins are likely to be associated with -type radicals but when the bias voltage is reduced below about 100 V, the protonated, fourfold coordinated, C bonding configurations increase more rapidly that the protonated, threefold coordinated ones. 36 However, for N s р10 18 cm Ϫ3 , the N s value will have little effect on the overall linewidth and ⌬B pp G values since the dipolar contribution is already so small.…”

Section: Prb 61mentioning

confidence: 99%

EPR linewidth variation, spin relaxation times, and exchange in amorphous hydrogenated carbon

2000

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Electron paramagnetic resonance ͑EPR͒ measurements have been made of amorphous hydrogenated carbon ͑a-C:H͒ films grown by plasma enhanced chemical vapor deposition ͑PECVD͒ with negative self-bias voltages V b in the approximate range 10-540 V. For V b Ͻ100 V, as the film changes from polymerlike to diamondlike, the changes in linewidth and shape are interpreted in terms of changes to two contributions-one due to dipolar interactions between the unpaired spins and one due to unresolved lines arising from hyperfine interactions with H 1 . The former yields a Lorentzian line, the latter a Gaussian, and the resultant spectrum has the Voigt shape. The empirical relation ⌬B pp G ͑in Gauss͒ϭ͑0.18Ϯ0.05͒ϫ͑at. % H) between the peak-to-peak Gaussian contribution ͑in Gauss͒ ⌬B pp G and the hydrogen content in atomic percentage is obtained. For V b Ͼ100 V the linewidth is shown to be dominated by the dipolar interactions and exchange and it decreases as V b increases; the change is shown to arise primarily from a change in the exchange interaction. Evidence for this comes from measurements which show that the spin-lattice relaxation time appreciably shortens and the spin-spin relaxation time lengthens as the bias voltage is increased. The magnitude and variation with bias of the linewidth are consistent with the EPR signal originating from the -type radicals.

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“…7 One of the key factors in determining the structure and properties of hard amorphous carbon films is the hybridization state of the atoms that form the amorphous network. 8 Previous results on a-C͑N͒:H films 9 allude to an increase in the graphitic clustering (sp 2 bonding͒ upon nitrogen incorporation, which may be correlated to the observed internal stress reduction. 5 A similar reduction in stress is observed for highly tetrahedral C:N films 10,11 in which nitrogen incorporation above 1 at.…”

mentioning

confidence: 96%

“…The f C(sp 2 ) value that we obtained for the nitrogen-free sample ͑Ϸ0.5͒ lies within the range normally observed in a-C:H films. 8 For the nitrogenated samples, in both cases, there is a steeper initial increase in the carbon sp 2 fraction for nitrogen contents smaller than 5 at. %.…”

mentioning

confidence: 99%

Influence of precursor gases on the structure of plasma deposited amorphous hydrogenated carbon–nitrogen films

Franceschini

Freire

Silva

1996

Applied Physics Letters

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The atomic structure of amorphous hydrogenated carbon-nitrogen films was studied by electron energy loss spectroscopy ͑EELS͒. The films were deposited onto Si͑100͒ substrates by rf plasma decomposition of CH 4 -NH 3 and CH 4 -N 2 mixtures, with substrates placed on the powered electrode of a diode glow-discharge system. The sp 2 fraction of C and N atoms as a function of the nitrogen content in the films was obtained by EELS analysis. An increase of the carbon sp 2 fraction with increasing fraction of NH 3 and N 2 feed gases was observed. The variation in the atomic structure of the a-C͑N͒:H thin films is correlated to the internal compressive stress. © 1996 American Institute of Physics. ͓S0003-6951͑96͒01319-8͔In the last few years there has been an increasing interest in the study of nitrogen incorporation into hard amorphous hydrogenated carbon ͑a-C:H͒ films. Research into the search for the proposed ␤-C 3 N 4 phase, which is predicted to be harder than diamond was initiated by Liu and Cohen. 1 As a result of nitrogen incorporation into carbon films it was found that both optical and electrical properties, 2-4 as well as their mechanical properties 5-7 can be modified. Particularly with respect to the mechanical properties, it was found that nitrogen incorporation results in a substantial reduction of the compressive internal stress of the films. The improvement in adhesion that resulted from the stress reduction has made it possible to use amorphous hydrogenated carbonnitrogen ͓a-C͑N͒:H͔ films as antireflective coatings in Ge based IR sensors. 7 One of the key factors in determining the structure and properties of hard amorphous carbon films is the hybridization state of the atoms that form the amorphous network. 8 Previous results on a-C͑N͒:H films 9 allude to an increase in the graphitic clustering (sp 2 bonding͒ upon nitrogen incorporation, which may be correlated to the observed internal stress reduction. 5 A similar reduction in stress is observed for highly tetrahedral C:N films 10,11 in which nitrogen incorporation above 1 at. % resulted in both stress reduction and increase in the sp 2 carbon fraction.All of the above-cited deposition studies on a-C͑N͒:H films are based on addition of N 2 to the deposition atmosphere, in the deposition of the a-C films. To date, few researchers have studied the use of ammonia as the source gas for nitrogen. 12,13 Contrary to the above research, Seth et al. 12 reported an increase in the sp 3 carbon atoms fraction upon nitrogen incorporation in a-C͑N͒:H films deposited by PECVD in C 4 H 6 -NH 3 atmospheres. In order to clarify the role of the nitrogen precursor gas on the structure and properties of a-C͑N͒:H films, we report a study on the influence of the precursor gases NH 3 and N 2 in the determination of they hybridization state of carbon and nitrogen atoms in a-C͑N͒:H films, as a function of the nitrogen content. The compressive internal stress was also measured and correlated with the other results.The a-C͑N͒:H films were produced by plasma decomposition of CH 4...

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Atomic constraint in hydrogenated ‘‘diamond-like’’ carbon

Cited by 245 publications

References 12 publications

Study of a-C:H thin films grown by PIII in different times for Mechanical and Tribological applications

Study of a-C:H thin films grown by PIII in different times for Mechanical and Tribological applications

EPR linewidth variation, spin relaxation times, and exchange in amorphous hydrogenated carbon

Influence of precursor gases on the structure of plasma deposited amorphous hydrogenated carbon–nitrogen films

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