Effects of nanoscale clustering in amorphous carbon

Abstract

In this review the effects of clustering associated with the sp 2 and sp 3 phases of amorphous carbon thin films are examined. We highlight that many of the optical and electronic properties of these films can be explained by consideration of disorder in the sp 2 phase. Within the context of topological and structural disorder, we explain the variation of the visible Raman line width, Raman shift, Tauc gap and Urbach energy as a function of deposition conditions. We further go on to describe how intra-sp 2 cluster interactions are responsible for the narrowing of the electron paramagnetic resonance line width with increasing spin density and how this intracluster interaction can be extended to the intercluster transport properties, in particular, for electron field emission from the films. We also examine how the mechanical properties of carbon films are affected by clustering which can be enhanced by thermal annealing.

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