Quantitative measurements of electromechanical response with a combined optical beam and interferometric atomic force microscope

Abstract

An ongoing challenge in atomic force microscope (AFM) experiments is the quantitative measurement of cantilever motion. The vast majority of AFMs use the optical beam deflection (OBD) method to infer the deflection of the cantilever. The OBD method is easy to implement, has impressive noise performance and tends to be mechanically robust. However, it represents an indirect measurement of the cantilever displacement, since it is fundamentally an angular rather than a displacement measurement. Here, we demonstrate a metrological AFM that combines an OBD sensor with a laser Doppler vibrometer (LDV) to enable accurate measurements of the cantilever velocity and displacement. The OBD/LDV AFM allows a host of quantitative measurements to be performed, including in-situ measurements of cantilever oscillation modes in piezoresponse force microscopy (PFM). As an example application, we demonstrate how this instrument can be used for accurate quantification of piezoelectric sensitivity -a longstanding goal in the electromechanical community.

Quantitative Electromechanical Atomic Force Microscopy

“…In direct contrast, when the IDS laser spot is positioned directly over the tip location (Figures 3c and 3d), a frequency-independent response (i.e., no cantilever resonance) and hysteresis free signal is measured. This result is in agreement with previous reports 35,36 that when the IDS spot is positioned directly over the tip, the detection signal is insensitive to the motion of the cantilever and detects only the displacement of the tip, a prerequisite for quantifying surface strain. This result also compounds the previous conclusion that in many cases, the butterfly loops are not a result of localized surface displacements under the tip; instead, they are an effect of the cantilever motion and the detection scheme, making them inherently sensitive to nonlocal electrostatic interactions acting on the body of the cantilever.…”

Probing of Local Multifield Coupling Phenomena of Advanced Materials by Scanning Probe Microscopy Techniques

“…In addition, various customized setups are developed, such as integrated SPM‐Raman and SPM‐IR. SPM with special excitation techniques are also invented, such as interferometric displacement sensor (IDS), blueDrive photothermal excitation, dual AC resonance tracking (DART), band excitation, PeakForce, and others. Furthermore, SPM can be placed inside a glovebox or integrated with an ultrahigh vacuum (UHV) system in order to precisely control the experimental environment or to conduct measurement at cryogenic temperature.…”

“…Moreover, ferroelectric‐like behaviors induced by charge injection and electrostatic force has been discriminated using contact Kelvin probe force microscopy (cKPFM) technique, and a simple AC sweep till high amplitude also helped to differentiate piezoelectric and nonpiezoelectric responses . More related information can be found in the review article by Seol et al On the other hand, a newly developed SPM technique adopting a laser Doppler vibrometer (LDV) was able to accurately measure the cantilever dynamics and thus contributed to quantify electromechanical strain …”

In-situ piezoresponse force microscopy cantilever mode shape profiling

“…"# ≈ . 65 Eq. (3) was solved analytically using Mathematica and then used to compute the theoretical EB spectrograms shown in Figures 4(e) and (e') and 5(a')-(c').…”