Figure 4
The topographic and potential images and the potential line profiles taken by FM- and HAM-KPFMs. (a, c) Topographic and (b, d) potential images taken simultaneously on the Ge (001) surface obtained by FM- and HAM-KPFMs, respectively. In the potential image, a bright (dark) spot indicates high (low) potential, which is repulsive (attractive) to electrons. (e, f) Cross-sectional profiles measured on the potential (b, d) images along the lines, respectively. The modulation frequency for FM (HAM)-KPFM is 500 Hz (1.045 MHz), respectively. Experimental parameters used in FM- and HAM-KPFMs: A = 6.5 nm, VAC = 150 mV, the frequency shift was set at -6.5 Hz for AFM imaging.