  We report an experimental investigation of the edge effect on the
room-temperature transport in graphene nanoribbon and graphene sheet (both
single-layer and bilayer). By measuring the resistance scaling behaviors at
both low and high carrier densities, we show that the transport of single-layer
nanoribbons lies in a strong localization regime, which can be attributed to an
edge effect. We find that this edge effect can be weakened by enlarging the
width, decreasing the carrier densities or adding an extra layer. From graphene
nanoribbon to graphene sheet, the data show a dimensional crossover of the
transport regimes possibly due to the drastic change of the edge effect.
