B. Ohler, R. Proksch, R. Wagner, R. Zhu, A. Gruverman, U. Schroeder, J. Lefever, J. Li, A. Labuda
Asylum Research,
United States
Keywords: atomic force microscopy, interferometry, contact resonance, force mapping, piezoresponse force microscopy
Summary:
Atomic Force Microscopes (AFMs) have become a standard tool for high resolution surface mapping of a wide variety of nanoscale samples. The vast majority of existing AFMs make use of an optical beam detector (OBD) that measures the bending of the flexible cantilever beam. Despite its popularity, accurate and reproducible mechanical measurements using this detection approach are challenging. Specific barriers to widespread accurate AFM include (i) highly inconsistent sensitivity calibrations, (ii) measurement noise floors significantly higher than thermal motion of the cantilever probes and (iii) uncontrolled mixing of vertical and in-plane forces acting on the tip. Component mixing inevitably complicates attempts at accurate mechanical measurements and can lead to enormous, and often unacknowledged uncertainties. In this presentation, we will demonstrate a series of new measurement workflows based around interferometry, 1 including a new quadrature phase differential interferometer (QPDI) that routinely achieves a detection noise down to ≈5 fm⁄√Hz using standard commercial cantilevers (Fig. 1a)). The QPDI measurement remains linear and accurate for large deflections (>1μm) down to sub-picometer thermal fluctuations. This improved noise and accurate calibration reveals details and features that have been hidden from view using conventional OBD measurements. In this presentation, we will show results functional ferroelectrics, including next generation computing materials such as HfO and HZO (Fig.1 b)). We will demonstrate a workflow that allows the full 3D polarization of samples to be imaged. An example of [100] BFO is shown in Fig. 1c).2 Finally, in addition to much improved accuracy of AFM measurements, QPDI detection has enabled a new version of resonance-enhanced imaging (iDART) that allows extremely high sensitivity mapping of nano-electromechanical properties.3 1 A. Labuda and R. Proksch, Applied Physics Letters 106 (25) (2015). 2 R. Proksch and R. Wagner, Small Methods 9 (7) (2025). 3 J. Bemis, F. Wunderwald, U. Schroeder, X. Xu, A. Gruverman, R. Proksch, https://arxiv.org/abs/2510.19063 (2025).