Piezoresistive AFM cantilevers surpassing standard optical beam deflection in low noise topography imaging

Abstract

Optical beam deflection (OBD) is the most prevalent method for measuring cantilever deflections in atomic force microscopy (AFM), mainly due to its excellent noise performance. In contrast, piezoresistive strain-sensing techniques provide benefits over OBD in readout size and the ability to image in light-sensitive or opaque environments, but traditionally have worse noise performance. Miniaturisation of cantilevers, however, brings much greater benefit to the noise performance of piezoresistive sensing than to OBD. In this paper, we show both theoretically and experimentally that by using small-sized piezoresistive cantilevers, the AFM imaging noise equal or lower than the OBD readout noise is feasible, at standard scanning speeds and power dissipation. We demonstrate that with both readouts we achieve a system noise of ≈0.3 Å at 20 kHz measurement bandwidth. Finally, we show that small-sized piezoresistive cantilevers are well suited for piezoresistive nanoscale imaging of biological and solid state samples in air.

High-bandwidth multimode self-sensing in bimodal atomic force microscopy

“…However, the authors believe that the procedure is closer to the actual dynamic AFM application (using lock-in demodulation of actively driven cantilevers) and therefore the values reported are a realistic representation of values obtained during AFM imaging. To qualify the resolution of the overall AFM system, a noise image with the actively driven cantilever in contact with the sample surface should be acquired [ 35 ] which takes into account all contributing noise processes.…”

A versatile atomic force microscope integrated with a scanning electron microscope

“…The AFSEM instrument, developed by GETec Microscopy GmbH (Vienna, Austria), uses piezo-resistive, self-sensing cantilevers. [16][17][18] In comparison, commercially available AFMs for the SEM typically use an optical lever 19 or tuning fork geometry. 20 The actuation and positioning of the cantilever are performed by piezoelectric ceramic multilayer actuators.…”

Atomic force microscope with an adjustable probe direction and piezoresistive cantilevers operated in tapping-mode / Im Tapping-Modus betriebenes Rasterkraftmikroskop mit einstellbarer Antastrichtung und piezoresistiven Cantilevern

“…The still ongoing development led to different approaches to measure the deflection of the cantilever [22]. While the optical beam deflection (OBD) method is still mainly used, the once inferior signal-to-noise ratio (SNR) of self-sensing methods, like the piezoresistive deflection measurement [21], has been improved steadily and is nowadays comparable to the SNR of OBD [6]. Besides the deflection detection, the measurement of vertical or near vertical surface features, features with a high-aspect-ratio or even undercut features is another important field of research.…”