▎ 摘　　要

Nanostructural effects on the thermoelectric power of graphene nanoribbons (GNRs) are revealed through first-principles simulation based on the density functional theory combined with nonequilibrium Green's function theory. The thermoelectric power of GNRs exhibits essentially different behavior depending on their edge structure and ribbon width. For zigzag-edged GNRs, the thermoelectric power shows a peculiar energy dependence originating from edge-localized electronic states with energy near the Fermi level. On the other hand, for armchair-edged GNRs (AGNRs), the thermoelectric power is classified into three categories depending on the ribbon width. Among AGNRs with similar ribbon width, an AGNR belonging to a category satisfying mod(N-a, 3) = 1 displays the largest thermoelectric power, where N-a is the integer determining the ribbon width of an AGNR. (c) 2013 The Japan Society of Applied Physics