Local coordination of carbon atoms in amorphous carbon

Tight-binding molecular-dynamics study of amorphous carbon

“…The initial configurations are liquid structures at 5000 K for each given density [15]. good agreement with the value of (6.5 4 1.5%) estimated by a nuclear magnetic resonance (NMR) study [10] on the same a-C sample used in the neutron scattering measurement [7]. However, the presence of twofold coordinated atoms was not considered in the data analysis of…”

“…Moreover, the percentage of fourfold atoms from the ab initio MD seems a bit too high compared with our result as well as the experimental data of Ref. [10]. We note that the energy of linear carbon chain (twofold) with respect to that of diamond (fourfold) and graphite (threefold) from our tight-binding model is 1.20 and 1.22 eV/atom, respectively, which are in excellent agreement with the values of 1.22 and 1.24 eV/atom obtained from converged first-principles local-densityapproximation (LDA) calculations [19,20].…”

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

“…This lack of knowledge inhibits developing a fundamental understanding of the mechanisms by which the excellent thermal stability and tribological performance of a-C:H:Si:O are achieved. To gain insights into the structure and composition of DLCs, some of the most powerful tools in the material characterization arsenal have been used, including Raman spectroscopy [9,[16][17][18][19], X-ray photoelectron spectroscopy (XPS) [13,20,21], near edge X-ray absorption fine structure (NEXAFS) spectroscopy [22][23][24], electron energy loss spectroscopy (EELS) [25], Fourier-transform infrared spectroscopy (FT-IR) [26], X-ray reflectivity (XRR) [25], forward recoil elastic scattering (FRES) [27], nuclear magnetic resonance (NMR) spectroscopy [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41], and electron paramagnetic resonance (EPR) spectroscopy [42][43][44][45][46].…”

“…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.…”

Ultraviolet and visible Raman spectroscopic investigations of nanocrystalline carbon thin films grown by bias‐assisted hot‐filament chemical vapor deposition

“…6,11 Although vibrational spectroscopic methods in principle can probe changes in bonding directly, they have not been successful with disordered forms of carbon such as those studied here. For example, nuclear magnetic resonance (NMR) spectroscopy 12,13 can detect sp 3 C atoms, but it requires thick samples, which are difficult to make because of high stress and consequent delamination. The same is also true for the inelastic neutron scattering (INS) technique.…”