Fig. 2.
Repeated imaging of the same sample area increases the resolution. Bias, setpoint current, scan size: a, b −1.2 V, 30 pA, 23.7 × 23.7 nm2 c −1.2 V, 20 pA, 23.7 × 23.7 nm2 d −1.2 V, 20 pA, 12.0 × 12.0 nm2 e −1.2 V, setpoint current change from 20 to 10 pA at the marked scan line, 12.0 × 7.8 nm2; and f −1.2 V, 10 pA, 12.0 × 12.0 nm2. Red circles indicate unstable clusters and some were removed by tip in in a, b . Repeated imaging of the same area with decreasing setpoint current improved the spatial resolution markedly. Images taken at the LHe temperature over the course of 7 min/image