NMR evidence for strained carbon bonding in tetrahedral amorphous carbon

Golzan, Mir Maqsood; Lukins, P. B.; McKenzie, David R.; Vassallo, Anthony M.; Hanna, John V.

doi:10.1016/0301-0104(94)00421-6

Cited by 34 publications

(19 citation statements)

References 15 publications

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“…Nevertheless, visible Raman can be used to determine the sp 2 /sp 3 fraction which has usually been extracted from shift or broadening of the peak that occurs at 1550cm -1 . 108 The accuracy of determining the sp 2 /sp 3 ratio is relatively low, 10%, but it does give the information quickly and non-destructively compared to the other techniques.…”

Section: Dlc Reviewmentioning

confidence: 99%

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

Hainsworth¹,

Uhure²

2007

International Materials Reviews

184

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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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Section: Dlc Reviewmentioning

confidence: 99%

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

Hainsworth¹,

Uhure²

2007

International Materials Reviews

184

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“…We compute H and C d TMS [20], and compare our results with experimental data obtained on two similar samples: a hydrogenated sample, at a density of 1.8 g͞cm 3 , with 35 at. % of H [1], and a pure-C sample at a density of 2.9 g͞cm 3 [2]. From the amount of fourfold coordinated C and the H content, these samples qualify as hard diamondlike films.…”

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confidence: 99%

“…Considerable efforts have been undertaken to understand the microscopic structure of these films. Nuclear magnetic resonance (NMR) is becoming increasingly important in this investigation, especially for the characterization of amorphous carbon [1][2][3][4], but also for the study of CVD diamond [5,6]. In Ref.…”

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confidence: 99%

“…We expand the wave functions in a plane wave basis set up to an energy cutoff of 70 Ry. Following the experimental convention, we will quote chemical shifts relative to the standard reference system of liquid tetramethylsilane (TMS) at room temperature [11], d TMS ͑sample͒ 2͓s͑sample͒ 2 s͑TMS͔͒ , (2) where s is the absolute chemical shift measured for a spherical shape.…”

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Ab initioNMR Chemical Shift of Diamond, Chemical-Vapor-Deposited Diamond, and Amorphous Carbon

1997

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The NMR chemical shift spectra of diamond, chemical-vapor-deposited (CVD) diamond, and diamondlike amorphous carbon are computed from first principles. The results of our calculation are in excellent agreement with experiments, and are useful for the interpretation of the NMR spectra in terms of the microscopic structure of the materials. In particular, we show that the NMR and Raman linewidths in polycrystalline CVD diamond are due to stress fluctuations, and we support a heterogeneous model for the amorphous hydrogenated phase. [S0031-9007(97)04072-6] PACS numbers: 76.60. Cq, 61.43.Bn, 71.15.Mb, 82.80.Ch Polycrystalline diamond thin films, grown by chemical vapor deposition (CVD), and diamondlike amorphous carbon thin films possess the outstanding physical properties of bulk diamond, such as high thermal conductivity, hardness, chemical inertness, and optical transparency in the infrared region. Their possible applications include wear-resistant coatings and thin-film semiconductor devices. For example, diamondlike amorphous carbon is currently used as a protective layer in magnetic disks. Considerable efforts have been undertaken to understand the microscopic structure of these films. Nuclear magnetic resonance (NMR) is becoming increasingly important in this investigation, especially for the characterization of amorphous carbon [1-4], but also for the study of CVD diamond [5,6]. In Ref.[7] we presented a novel theory for the ab initio computation of NMR chemical shifts (s) in condensed matter systems. Our formalism overcomes the limitations of all previous approaches [8], which could handle only isolated molecules or clusters, and it can be applied to periodic crystals or, with a supercell technique, to amorphous materials. In this Letter we present the first ab initio calculations of carbon chemical shifts in crystalline and amorphous solids. We compute the chemical shift spectra of diamond, CVD diamond, and diamondlike amorphous carbon with and without hydrogen. Our results are in excellent agreement with experiments, and are useful for the interpretation of NMR spectra in terms of the microscopic structure of the materials.A uniform, external magnetic field B ext applied to a sample of matter induces an electronic current which produces a nonuniform magnetic field, B in ͑r͒. The chemical shift is defined as the ratio between the induced magnetic field and the external uniform applied magnetic field,Here s $ ͑r͒ is the chemical shift tensor, and s͑r͒ Tr͓s $ ͑r͔͒͞3. This magnetic response is a fingerprint of the microscopic structure of the material under study. NMR measures s͑r͒ at the nuclear positions. We denote with H s the chemical shifts at the hydrogen nuclei, and with C s the chemical shifts at the carbon nuclei.We compute s following Ref.[7]. The electronic structure is described using density functional theory in the local density approximation. As the core contributions for C are insensitive to the chemical environment [8], we consider the magnetic response of the valence electrons only. We use...

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“…Pan et al [39], Golzan et al [34] and Jäger et al [36] effectively employed NMR spectroscopy for gaining insights into the carbon hybridization states in sputtered a-C and tetrahedral amorphous carbon (ta-C). Besides providing information about the carbon hybridization state, NMR can also be used for investigating the evolution of the local structure of ta-C upon annealing [28,29]: for example, on the basis of the peak lineshape and width, Alam et al concluded that the reordering of sp 2 -and sp 3 -bonded carbon atoms, rather than rehybridization from fourfold-to threefold-coordinated carbon, which is known to occur at much higher temperatures, is the mechanism leading to stress relaxation in ta-C upon annealing.…”

Section: Introductionmentioning

confidence: 99%

Solid state magnetic resonance investigation of the thermally-induced structural evolution of silicon oxide-doped hydrogenated amorphous carbon

Peng

Sergiienko

Mangolini

et al. 2016

Carbon

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NMR evidence for strained carbon bonding in tetrahedral amorphous carbon

Cited by 34 publications

References 15 publications

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

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

Ab initioNMR Chemical Shift of Diamond, Chemical-Vapor-Deposited Diamond, and Amorphous Carbon

Solid state magnetic resonance investigation of the thermally-induced structural evolution of silicon oxide-doped hydrogenated amorphous carbon

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