Nonlinear transport imaging by scanning impedance microscopy

Scanning probe microscopy is an established tool for characterization of the linear static and frequency-dependent lateral electronic transport in materials and devices at the nanoscale. In this letter, a modified scanning impedance microscopy (SIM) technique is proposed to extend the nanoscale transport measurements of intrinsic material properties to the nonlinear regime, through detection of frequency harmonics, and exemplified by a detailed study of a prototypical metal-semiconductor interface. The imaging mechanism, surface - tip contrast transfer, optimal experimental conditions, and potential applications of nonlinear SIM are discussed. This technique can be readily transferred to most cantilever-based scanning probe microscopes.