Design and fabrication of micro-cantilevers for multi-frequency atomic force microscopy

Several multi-frequency operation modes have recently been proposed that exhibit significant promise in terms of their ability to discern various material properties. In this article, we report the design, fabrication and characterization of cantilevers with integrated actuation and conductive probes for multi-frequency atomic force microscopy (AFM). The cantilevers are equipped with aluminum nitride piezoelectric actuators and platinum silicide tips. The integrated actuation results in a significantly improved dynamic behavior as compared to the use of external piezo-actuators. The platinum silicide tips provide excellent electrical sensing capability. These cantilevers also possess a stepped-rectangular geometry that ensures that the resonance frequencies corresponding to the first four normal bending modes fall within a frequency range of 1 MHz. The dynamic behavior of these cantilevers is explored using both finite element simulations and experimental methods. These cantilevers exhibit excellent dynamic behavior over a wide frequency range, both off-contact and on-contact with a sample. Imaging experiments utilizing higher eigenmodes as well as bimodal imaging are presented. Also shown is the use of these cantilevers for normal force modulation for enhanced electrical sensing capability.