2014/04/03 by Yang, Yanfei, Huang, Lung-I, Fukuyama, Yasuhiro +6
#FOS: Physical sciences #Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
paper · doi:10.48550/arxiv.1404.1048
Monolayer epitaxial graphene (EG) grown on hexagonal Si-terminated SiC substrates is intrinsically electron-doped (carrier density is about 1013 cm^(-2)). We demonstrate a clean device fabrication process using a precious-metal protective layer, and show that etching with aqua regia results in p-type (hole) molecular doping of our un-gated, contamination-free EG. Devices fabricated by this simple process can reach a carrier density in the range of 1010 cm^(-2) to 1011 cm^(-2) with mobility about 8000 cm2/V/s or higher. In a moderately doped device with a carrier density n = 2.4 x 1011 cm^(-2) and mobility = 5200 cm2/V/s, we observe highly developed quantized Hall resistance plateaus with filing factor of 2 at magnetic field strengths of less than 4 T. Doping concentrations can be restored to higher levels by heat treatment in Ar, while devices with both p-type and n-type majority carriers tend to drift toward lower carrier concentrations in ambient air.