Characterization of nano-electro-mechanical systems (NEMS) using photoacoustic microscopy

Abstract

A photoacoustic microscopy system has been developed for the noncontact characterization of materials at the micro- and nanometer scale. The system uses an electroabsoption modulated laser source for material excitation and a path-stabilized interferometer to detect the resulting displacements. Using this system, we describe the optical excitation and detection of high-frequency nanoelectromechanical systems (NEMS) at am-bient temperature and pressure. Using a tightly focused modulated laser source, we have actuated the out-of-plane flexural resonances of bi-layered doubly clamped nanomechanical beams. The optically detected displacement profiles in these beams are consistent with a model where the absorbed laser power results in a local temperature rise and a subsequent thermally induced bending moment. The excitation technique allows probing and actuation of NEMS with excellent spatial and temporal resolution. From a device perspective, the technique offers immense frequency tunability and may enable future NEMS that can be remotely accessed thus obviating the need for electronic coupling. [The authors gratefully acknowledge funding from National Science Foundation under Grants ECS-0304446 and ECS-0210752.]