Structural characterization of carbon nanosheets via x-ray scattering

Abstract

The structure of carbonnanosheets deposited by radio frequency plasma-enhanced chemical-vapor deposition at different substrate temperatures is investigated via x-ray scattering.Carbonnanosheets consist of vertically aligned graphene-layer stacks, one to nine layers thick, which can attain micron-scale lengths. Histograms of both molecule length and thickness are generated by fitting the experimental data with a linear combination of x-ray scattering intensities, which are calculated for rhombus-shaped molecules of different dimensions. These histograms show that the average uncorrugated length within a nanosheet decreases from 107 Å at a 670 ° C deposition temperature to 50 Å at 950 ° C . The distribution of nanosheet thickness remains qualitatively similar at each deposition temperature, but decreases from an average of eight graphene layers at 670 ° C to about six layers at 950 ° C . With increasing temperature large nestlike structures are observed, but are found to consist of the same nanosheet constituents in a more corrugated and bunched form. These changes are accompanied by the transition from a primarily turbostratic structure with some ordered graphite crystallites at 670 ° C to a completely turbostratic structure with amorphous content at 950 ° C . All x-ray scattering results are explained in the context of the nanosheet morphology observed with scanning electron microscopy, and corroborating structural information is provided by Raman spectroscopy.