▎ 摘　　要

Despite its superb electronic properties, the semi-metallic nature of graphene with no band gap (E-g) at the Dirac point has been a stumbling block for its industrial application. We report an improved means of producing a tunable band gap over other schemes by doping low energy (10 eV) potassium ions (K+) on single layer graphene formed on 6H-SiC(0001) surface, where the noble Dirac nature of the pi-band remains almost unaltered. The changes in the pi-band induced by K+ ions reveal that the band gap increases gradually with increasing dose (theta) of the ions up to E-g = 0.65 eV at theta = 1.10 monolayers, demonstrating the tunable character of the band gap. Our core level data for C 1s, Si 2p, and K 2p suggest that the K+-induced asymmetry in charge distribution among carbon atoms drives the opening of band gap, which is in sharp contrast with no band gap when neutral K atoms are adsorbed on graphene. This tunable K+-induced band gap in graphene illustrates its potential application in graphene-based nano-electronics. Published by AIP Publishing.