Effects of deposition temperature on the properties of hydrogenated tetrahedral amorphous carbon

Sattel, S.; Robertson, John; Ehrhardt, H.

doi:10.1063/1.366193

Cited by 132 publications

(45 citation statements)

References 67 publications

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“…Nevertheless increasing the sp 2 content is still expected to increase the cluster size and decrease the gap. As noted earlier, many authors 6,8,12,13,25 have put forward the hypothesis that the Lorentzian line shape arises from exchange narrowing and that the reduction in the linewidth as the sp 2 content increases is associated with the greater delocalization of the unpaired electrons as the cluster size increases. It should be noted, however, that it is the increased overlap of the wave functions brought about by the greater delocalization rather than the greater delocalization itself which increases the strength of the exchange interaction.…”

Section: B Analysis Of Linewidth Variation For V B ð100 Vmentioning

confidence: 99%

“…Whether the film is a-C:H, ta-C:H, or ta-C, the decrease in ⌬B pp , in this higher bias region, is always accompanied by a decrease in the optical gap and an increase in the sp 2 fraction; 8-13 a correlation of linewidth and gap has already been noted. 25 Regarding the gap, Robertson and O'Reilly 2 showed that the most stable arrangement of sp 2 sites is in compact clusters of fused six- fold rings and that the gap varies inversely as the cluster size. This model was later modified 26 to account for the reduction in clustering produced by disorder and the presence of olefinic chains as well as aromatic rings.…”

Section: B Analysis Of Linewidth Variation For V B ð100 Vmentioning

confidence: 99%

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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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Section: B Analysis Of Linewidth Variation For V B ð100 Vmentioning

confidence: 99%

Section: B Analysis Of Linewidth Variation For V B ð100 Vmentioning

confidence: 99%

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

2000

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“…The roughness of DLC films has been shown to depend on the various deposition methods 163,164 and deposition parameters such as ion energy, [165][166][167][168][169][170] gas mixture 163 and bias voltage. 169 Coating roughness is also dependent on substrate material [171][172][173] and the underlying substrate roughness.…”

Section: Dlc Reviewmentioning

confidence: 99%

Diamond like carbon coatings for tribology: production techniques, characterisation methods and applications

Hainsworth¹,

Uhure²

2007

International Materials Reviews

180

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There are numerous types of surface coatings available to engineers in order to improve the friction and wear resistance of components. In order to successfully use these coatings in practice, it is important to understand the different types of coatings available, and the factors that control their mechanical and tribological properties. This paper will focus on the application of diamond-like carbon (DLC) coatings in tribological applications. Thus far, DLC coatings have found broad industrial application, particularly in optical and electronic areas. In tribological applications, DLC coatings are now being used successfully as coatings for ball bearings where they decrease the friction coefficient between the ball and race, in shaving applications where they increase the life of razor blades in wet shaving applications, and increasingly in automotive applications such as racing engines and standard production vehicles.The structure and mechanical properties of DLC coatings are dependent on the deposition method and the incorporation of additional elements such as nitrogen, hydrogen, silicon and metal dopants. These additional elements control the hardness of the resultant film, the level of residual stress and the tribological properties. As diamond-like carbon films increasingly become adopted for use in industry, it is important to review the factors that control their 2 of 42 DLC Reviewproperties, and thus, the ultimate performance of these coated components in practical tribological applications.

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“…This variation in elastic behaviour cannot be described by a stress induced phase transition from sp 2 to sp 3 bondings which is observed for deposition of amorphous carbon at room temperature. It is well described by the subplantation process [21][22][23]. As Sattel et al could show [23], heating the substrate to temperatures over about 250 °C prevents the film material to become diamond-like.…”

Section: Resultsmentioning

confidence: 99%

Characterization of elastic properties of hard carbon and boron nitride films using the Brillouin light scattering technique

et al. 2000

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The elastic properties of thin graphitic carbon and hexagonal boron nitride films have been determined by Brillouin light scattering from thermally excited surface acoustic phonons. The carbon films have been grown by plasma beam deposition at 420 o C. The BN films have been deposited by rf-magnetron sputtering and simultaneous ion plating. In the case of amorphous carbon a layered substructure has been found with a rather compliant intermediate layer at the interface. The stiffness of the films increases with increasing ion energy. As for carbon the BN coatings exhibit a pronounced elastic anisotropy indicating a preferred orientation of the hexagonal planes perpendicularly to the surface. The comparison of the Young´s moduli determined by load indentation and by Brillouin light scattering allows the conclusion that the material is composed of two or more components of different stiffness.Films grown by magnetron sputtering or plasma beam deposition are in general nanocrystalline or amorphous and do not exhibit single crystal properties. Their elastic properties need to be determined experimentally because they depend strongly on the deposition conditions, and they can in general not be derived from theoretical considerations. Brillouin light scattering (BLS) is a well established technique to obtain information on elastic properties of thin films by measuring the frequency shift of light scattered inelastically from phonons [1,2]. The information obtained by BLS usually allows to determine several independent elements of the elastic tensor and to reveal the existence of an interlayer between film and substrate. Sample PreparationBoron nitride films have been grown on (100)-silicon by 13.56 MHz rf magnetron sputtering from a polycrystalline stoichiometric BN target in a pure argon atmosphere of about 4·10 -4 mbar. The apparatus has been described in detail earlier [3]. On account of the unbalanced magnet configuration a rather high flux of argon ions can be extracted from the plasma by applying a rf bias to the substrate. The energy of the ions was near 130 eV. At an ion current density of 1.2 mA/cm 2 at the substrate the growth rate was found to be 6.2 nm/min. The argon ion flux to the substrate was about a factor of 7 larger than the flux of boron and nitrogen atoms contributing to the film growth. The substrate temperature was held constant at 350 o C. Under these conditions boron nitride films grow in the hexagonal modification [4,5] which has been controlled by infrared spectroscopy. Carbon films with a hydrogen content of 5% have been produced by plasma beam deposition on a (001) silicon substrate heated to 420 o C. The plasma beam source, which has been described in detail previously in [6], consists of a capacitive, magnetically confined r.f. discharge. Acetylene was used as working gas because it forms almost exclusively C 2 H 2 + -ions in low pressure plasmas [6]. The fraction of this ion species was larger than 95% at a background pressure of 6·10 -5 mbar. The films presented here were grown at ion e...

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Effects of deposition temperature on the properties of hydrogenated tetrahedral amorphous carbon

Cited by 132 publications

References 67 publications

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

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

Diamond like carbon coatings for tribology: production techniques, characterisation methods and applications

Characterization of elastic properties of hard carbon and boron nitride films using the Brillouin light scattering technique

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