Electrostatic-free piezoresponse force microscopy

Abstract

Contact and non-contact based atomic force microscopy (AFM) approaches have been extensively utilized to explore various nanoscale surface properties. In most AFM-based measurements, a concurrent electrostatic effect between the AFM tip/cantilever and sample surface can occur. This electrostatic effect often hinders accurate measurements. Thus, it is very important to quantify as well as remove the impact of the electrostatic effect on AFM-based measurements. In this study, we examine the impact of the electrostatic effect on the electromechanical (EM) response in piezoresponse force microscopy as a model AFM mode. We quantitatively studied the effects of increasing the external electric field and reducing the spring constant of a cantilever. Further, we explored ways to minimize the electrostatic effect. The results provide broad guidelines for quantitatively analyzing the EM response as well as, eventually, for obtaining the electrostatic-free EM response. The conclusions can be applied to other AFM-based measurements that are subject to a strong electrostatic effect between the AFM tip/cantilever and sample surface, regardless of contact and non-contact modes.

Exploring Anomalous Polarization Dynamics in Organometallic Halide Perovskites

“…that can further mask intrinsic materials properties . In addition, dynamic PFM is known to be influenced by electrostatic contributions originating from nonlocal forces acting on the tip, particularly when using soft cantilevers (approximately few N m −1 ), or studying poor ferroelectric samples, meaning electrostatic contributions are often nonnegligible . In particular, PFM switching experiments are prone to artefacts, where high dc‐voltage pulses are applied to induce ferroelectric polarization switching, but can also cause charge injection or activate chemical processes.…”

Accurate electromechanical characterization of soft molecular monolayers using piezo force microscopy

“…The only exception is for the peptoid B SAMs, in which the tip-response curve yields an exponent close to À1.0, suggesting that the peptoid lm is signicantly stiffer than the other lms, as conrmed by AMFM measurements discussed below, and consistent with expectations of a peptoid PPI helix. 27 While eqn (2) allows an approximate conversion of k l to k c values, assuming a uniform shi from the fundamental frequency of the lever to the measured frequency of the lever while interacting with surface, k c was also measured directly using amplitude modulated force microscopy (AMFM). 10,[30][31][32] Due to the trends observed in the original k l measurements, the respectively, were chosen as the relative extremes of contact stiffnesses observed in the initial study, (Table in ESI †).…”

“…This indicates that a static V DC determined by sKPFM cannot be used directly to eliminate the electrostatic component of the measured response, as has been previously suggested. 27 Further Fig. 5A represents the equivalent of eight experimental runs on one sample using the more traditional AC sweep method, thus conrming the repeatability of the new measurement system and the lack of dielectric brake down of the lms due to the applied elds.…”

“…25 More recently, several groups have tried to reduce/eliminate these distortions by using high spring-constant (k l ) levers, with or without a xed external DC eld, or by creating new lever technologies, such as "inner paddled levers". 2,3,[26][27][28] These techniques reduce the electrostatic component of the measurement for specic cases; however, this may not be true for systems, such as organic polymers and biomaterials, in which the electrostatic component is quite large or where the Young's modulus of the material is small in comparison to the lever.…”

Nanoscale Probing of Ferroelectric Domain Switching Using Piezoresponse Force Microscopy

“…4,7,8,[10][11][12][13] These electrostatic artifacts can be reduced by using sufficiently stiff cantilevers, i.e., with high spring constants (e.g., above 40 N/m). 4,14) In addition, hysteretic surface charging 15,16) or ionic motion 11,[17][18][19][20][21] can generate PFM-like responses even in nonferroelectric samples. Therefore, one should be careful when interpreting PFM data.…”