Elastic constants of tetrahedral amorphous carbon films by surface Brillouin scattering

Abstract

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Thermal expansion coefficient of hydrogenated amorphous carbon

“…3͑c͒, and is comparable to the results obtained in the present work. Similar results have also been found for a ta-C:H film ͓with a higher Young's modulus ͑ϳ300 GPa͒ due to the higher sp 3 c-C concentration͔ by Ferrari et al 17 using Brillouin scattering.…”

Acoustic Microscopy and Surface Brillouin Scattering of Amorphous Carbon Pressure-Synthesized From C60

“…Heating the fullerite up to 1000-1300 K under the pressure 3 to 8 GPa leads to a formation of disordered phases with carbon atoms predominantly in sp 2 states. Heating C 60 at P>8 GPa results in formation of three-dimensional (3-D) polymerized amorphous phases of C 60 , with large number of sp 3 atomic sites [7] and nanocrystalline composites (nanoceramics) of diamond and graphite [8], fueling the most recent debates on the existence of ultrahard fullerene-based phases with hardness higher than diamond [9]. The structure of all these phases contain large amount of 4-fold sp 3 atomic states.…”

“…Recent interest in new superhard materials triggered by the discovery of the fullerene molecule C 60 has led to a series of extensive experimental studies of amorphous and nanocrystalline carbon phases and their properties in both bulk [1] and deposited as a thin film [2][3][4] states. Heating at relatively low pressures (P<8 GPa) has revealed one-dimensional (l-D)-and twodimensional (2-D)-polymerization [5] of C 60 and subsequent collapse of the fullerene structure into graphite-like disordered carbon [6].…”

Low-frequency eigenvibrations of hollow carbon microspheres

“…The observed mode frequencies are much lower than the bulk longitudinal acoustic mode frequency of 96 GHz calculated based on the mechanical properties ͑Young's modulus= 757 GPa, shear modulus = 337 GPa, bulk modulus= 334 GPa, density= 3.26 g / cm 3 ͒ determined by Ferrari et al for 76-nm-thick carbon films. 18 Thus, the observed Brillouin peaks cannot be due to bulk acoustic modes of carbon and are attributed to vibrational eigenmodes of the outer spherical shell.…”

“…The sound velocities of V l = 15 500 m / s and V t = 10 185 m / s were used as input parameters in the following computation. They were obtained from the mechanical properties of the carbon film studied by Ferrari et al 18 Parameters of this carbon film were chosen as our outer spherical shell thickness of 35 nm is of the same order as the film thickness. Next, the eigenfrequencies of spheroidal modes, with even l, were calculated for l values up to 12 and for n values up to 2, as we are interested in only the frequency region below 20 GHz.…”