High-Bandwidth AFM Probes for Imaging in Air and Fluid

Due to the high mechanical bandwidth of an integrated diffraction-grating-based force sensor, interdigitated AFM probes enable probing the nanomechanical properties of the sample by measuring fast varying tip-sample interaction forces while operating in tapping mode. To explain the mechanical frequency response obtained from finite-element analysis, we developed an analytical model that incorporates the higher order flexural modes of a cantilever. To enable flexibility necessary to use the probes in different imaging environments, a step is introduced into the batch fabrication where high-stress nitride is used. This step allows the probe to be used in various optical conditions such as different laser wavelengths (in the light-lever configuration), incident angles, and ambient refractive indices (such as air and water). We demonstrate that the probe can operate in both air and fluid and measure fast varying tip-sample interactions by imaging a sputtered gold film in both conditions.