Atomically resolved dynamic force microscopy operating at 4.7MHz

We demonstrate atomically resolved frequency modulation dynamic force microscopy operating at 4.7MHz using the third flexural mode of a silicon cantilever. A high spring constant due to the higher mode realized stable imaging with an amplitude of 2Å, which was calculated to be a favorable value for high-resolution imaging. Although excessive stiffness decreases the sensitivity of the detection, a stable imaging was realized with a low noise heterodyne laser Doppler interferometer and a narrow bandwidth feedback circuit. An atomically resolved constant frequency shift images of the Si(111)-7×7 were obtained with the exposed and terminated dangling bonds at the tip apex.