Bandgap broadening at grain boundaries in single-layer MoS2

摘要

Two-dimensional semiconducting transition-metal dichalcogenides have attracted considerable interest owing to their unique physical properties and future device applications.In particular,grain boundaries (GBs) have been often observed in single-layer MoS2 grown via chemical vapor deposition,which cansignificantly influence the material properties.In this study,we examined the electronic structures of various GBs in single-layer MoS2 grown on highly oriented pyrolytic graphite using low-temperature scanning tunneling microscopy/spectroscopy.By measuring the local density of states of a series of GBs with tilt angles ranging from 0° to 25°,we found that the bandgaps at the GBs can be either broadened or narrowed with respect to the intrinsic single-layer MoS2.The bandgap broadening shows that the GBs can become more insulating,which may directly influence the transport properties of nanodevices based on polycrystalline single-layer MoS2 and be useful for optoelectronics.