Point defect-induced transport bandgap widening in the downscaled armchair graphene nanoribbon device

We report on ab initio study of the electronic states and transport characteristics for armchair graphene nanoribbon devices with point defects. Geometric optimization of the point defect channel revealed the self-organizing property of the graphene. Density of state (DOS) calculation shows the point defect-induced gap states. However, the quantum transport calculations revealed that these defect-induced gap states are not contributing to the carrier transport across the channel. This is clarified further from the wavefunction analysis, which shows the spatial localization of the wavefunction around the defect regions. Most importantly, the widening of the transport bandgap with the increase in number of point defects was found even though the DOS bandgap remains unchanged. The impact of these point defects on the device characteristics varies depending on their type and location in the channel. The orientation of the defects plays a vital role in the carrier scattering, which is a crucial factor to be considered in downscaled devices.