1.IntroductionrnMicro-topology is of fundamental significance to materials,the properties of which are largely correlated with their inner features,be it orientation pattern,grain boundaries and micromorphology,to name a few[1-7].For subtle nano-architectures,such depen-dence is rather more noticeable.Specifically,the size,edges and orientation of some low dimensional nanostructures-in the form of sheets and ribbons-are consequential for their magnetic,elec-tric and mechanical properties,as revealed by theoretical studies[1,2];the micromorphology of solid surfaces plays an important part in determining their wetting properties[3,4];grain bound-aries are essential to various catalytic processes[5-7].