Figure 1
STS spectra at an atomically flat area of the nitrogen-doped graphite surface show Landau levels of bilayer graphene (massive Dirac fermion).
(a–c) STM images ((a) 300 mV, 59.4 pA, 1000 × 1000 nm2; (b) 300 mV, 59.1 pA, 200 × 200 nm2; (c) −500 mV, 96.6 pA, 50 × 50 nm2)). (d) STM image at the position shown by the white square in (c) (−500 mV, 97.4 pA, 7 × 7 nm2). (e) Line profile of the white dashed line in (d). (f) STS obtained at positions labelled A, B, C and D in (d). (g) Linear scaling between the peak positions in the STS and 
. Error bars indicate the variations in ten measurements at each position (see Figure S7).
