  While preserving many of the unusual features of single-layer graphene,
few-layer graphene (FLG) provides a richness and flexibility of electronic
structure that render this set of materials of great interest for both
fundamental studies and applications. Essential for progress, however, is an
understanding of the evolution of the electronic structure of these materials
with increasing layer number. In this report, the evolution of the electronic
structure of FLG, for N = 1 - 8 atomic layers, has been characterized by
measurements of the optical conductivity spectra. For each layer thickness N,
distinctive peaks are found in the infrared range, with positions obeying a
simple scaling relation. The observations are explained by a unified
zone-folding scheme that generates the electronic structure for all FLG
materials from that of bulk graphite.
