Grain Boundary Structures and Electronic Properties of Hexagonal Boron Nitride on Cu(111)

Grain boundaries (GBs) of hexagonal boron nitride (h-BN) grown on Cu(111) were investigated by scanning tunneling microscopy/spectroscopy (STM/STS). The first experimental evidence of the GBs composed of square-octagon pairs (4 vertical bar 8 GBs) was given, together with those containing pentagon-heptagon pairs (5 vertical bar 7 GBs). Two types of GBs were found to exhibit significantly different electronic properties, where the band gap of the 5 vertical bar 7 GB was dramatically decreased as compared with that of the 4 vertical bar 8 GB, consistent with our obtained result from density functional theory (DFT) calculations. Moreover, the present work may provide a possibility of tuning the inert electronic property of h-BN via grain boundary engineering.