▎ 摘　　要

We present the width dependent study of edge distribution of graphene nanoribbons unzipped from multi-wall nanotubes. The partial unzipping of the carbon nanotubes yields a mixture of carbon nanotubes and nanoribbons. Comparing atomic resolution images of scanning tunneling microscopy with the lattice of graphene, the edge structures of nanoribbons are identified. Below 10 nm, the edges are closer to armchair type. Above 20 nm, the ribbons prefer to have edges close to zigzag type. In between, a more random distribution of the edges is found. The findings are of potential usages for the edge control in graphene nanoribbon based applications. (C) 2013 AIP Publishing LLC.