Effect of Boundary Scattering on Magneto-Transport Performance in BN-Encapsulated Graphene

Abstract

For conductors in the ballistic regime, electron-boundary scattering at the sample edge plays a dominant role in determining the transport performance, giving rise to many intriguing phenomena like low-field negative magnetoresistance effect. We systematically investigate the magneto-transport behaviors of BN-encapsulated graphene devices with narrow channel width W, wherein the bulk mean free path L mfp can be very large and highly tunable. By comparing the magnetoresistance features and the amplitude of L mfp in a large parameter space of temperature and carrier density, we reveal that the boundary-scattering-dominated negative magnetoresistance effect can still survive even when the ballistic ratio (L mfp/W) is as low as 0.15. This striking value is much smaller than the expected value for achieving (quasi-) ballistic transport regime (L mfp/W ≥ 1), and can be attributed to the ultra-low specularity of the sample edge of our graphene devices. These findings enrich our understanding of the effects of boundary scattering on channel transport, which is of vital importance for future designs of two-dimensional electronic devices with limited lateral sizes.