Multimodal cantilevers with novel piezoelectric layer topology for sensitivity enhancement

Abstract

Self-sensing techniques for atomic force microscope (AFM) cantilevers have several advantageous characteristics compared to the optical beam deflection method. The possibility of down scaling, parallelization of cantilever arrays and the absence of optical interference associated imaging artifacts have led to an increased research interest in these methods. However, for multifrequency AFM, the optimization of the transducer layout on the cantilever for higher order modes has not been addressed. To fully utilize an integrated piezoelectric transducer, this work alters the layout of the piezoelectric layer to maximize both the deflection of the cantilever and measured piezoelectric charge response for a given mode with respect to the spatial distribution of the strain. On a prototype cantilever design, significant increases in actuator and sensor sensitivities were achieved for the first four modes without any substantial increase in sensor noise. The transduction mechanism is specifically targeted at multifrequency AFM and has the potential to provide higher resolution imaging on higher order modes.

Magnetic Force Microscope Image Evaluation of Magnetic Iron Oxide Floppy Disc With Various Lift Heights

“…However, in the floating method, the repulsive force between the atoms is very small to be able to image the surface topography of the sample. To solve this problem, it can be used to vibrate the cantilever piezoelectric modulator around the resonance frequency as close as possible to the sample surface and further correlate the changes to surface topography cantilever vibration [7]. The method was then referred to as the floating method, also known as the method of alternating current detection and proved to have a much higher sensitivity than the touch meth-od.…”

Multimodal atomic force microscopy with optimized higher eigenmode sensitivity using on-chip piezoelectric actuation and sensing

“…A number of integrated actuation methods have been developed over the years to replace the piezo-acoustic excitation [21][22][23], however only electro-thermal [24] or piezoelectric actuation [25] can be directly integrated on the cantilever chip. Compared to the optical beam deflection sensor, strain-based deflection measurements such as piezoelectric [26] and piezoresistive sensing [27] yield a much more compact form factor, and increased sensitivity for smaller cantilever dimensions [28][29][30] and higher order eigenmodes [31].…”

Soft Three-Dimensional Microscale Vibratory Platforms for Characterization of Nano-Thin Polymer Films

“…Consequently, the operation of most MEMS relies on a single vibration mode, thereby restricting their capability, for example, in detecting anisotropic mechanical properties in certain biological − and composite − thin-film materials. Access to multimodal resonances in 2D MEMS platforms typically requires non-idealities and asymmetries in nanomechanical resonators, or advanced actuation techniques using collections of piezoelectric components or patterned illumination with structured laser beams, but the consequent engineering complications create challenges in scaling and adapting to complex materials systems. A potential alternative strategy relies on three-dimensional (3D) vibrational structures with multimodal and tunable resonances, , formed by microfabrication and controlled assembly. − Reported methods in actuation via thin-film piezoelectric elements require, however, multistep fabrication processes, and they operate over a limited range of frequencies.…”

“…Consequently, the operation of most MEMS relies on a single vibration mode, thereby restricting their capability, for example, in detecting anisotropic mechanical properties in certain biological 19−21 and composite 22−26 thin-film materials. Access to multimodal resonances in 2D MEMS platforms typically requires nonidealities and asymmetries in nanomechanical resonators, 27 or advanced actuation techniques using collections of piezoelectric components 28 or patterned illumination with structured laser beams, 29 but the consequent engineering complications create challenges in scaling and adapting to complex materials systems.…”