Towards nanoscale electrical measurements in liquid by advanced KPFM techniques: a review

Abstract

Fundamental mechanisms of energy storage, corrosion, sensing, and multiple biological functionalities are directly coupled to electrical processes and ionic dynamics at solid-liquid interfaces. In many cases, these processes are spatially inhomogeneous taking place at grain boundaries, step edges, point defects, ion channels, etc and possess complex time and voltage dependent dynamics. This necessitates time-resolved and real-space probing of these phenomena. In this review, we discuss the applications of force-sensitive voltage modulated scanning probe microscopy (SPM) for probing electrical phenomena at solid-liquid interfaces. We first describe the working principles behind electrostatic and Kelvin probe force microscopies (EFM & KPFM) at the gas-solid interface, review the state of the art in advanced KPFM methods and developments to (i) overcome limitations of classical KPFM, (ii) expand the information accessible from KPFM, and (iii) extend KPFM operation to liquid environments. We briefly discuss the theoretical framework of electrical double layer (EDL) forces and dynamics, the implications and breakdown of classical EDL models for highly charged interfaces or under high ion concentrations, and describe recent modifications of the classical EDL theory relevant for understanding nanoscale electrical measurements at the solid-liquid interface. We further review the latest achievements in mapping surface charge, dielectric constants, and electrodynamic and electrochemical processes in liquids. Finally, we outline the key challenges and opportunities that exist in the field of nanoscale electrical measurements in liquid as well as providing a roadmap for the future development of liquid KPFM.

Optical, Dielectric and Magnetic Properties of La1−xNdxFeO3 Powders and Ceramics

“…KPFM analysis showed high quality homogeneity of all compositions (see Supplementary Materials, Figure S1). The only variation of contact potential difference was found at the grain boundaries, which can be attributed to typical artifacts of KPFM measurements [16]. Measured contact potential difference values increased slightly with doping, due to apparent variation of the electronic structure of the material with composition.…”

“…AFM was done using commercial scanning probe microscope Ntegra Aura (NT-MDT Spectral Instruments, Moscow, Russia) by Budget Sensors ElectriTap300-G tips with the curvature less 25 nm, resonance frequency about 300 kHz and 20 N/m force constant. In order to clarify chemical homogeneity at the local scale, we used Kelvin probe force microscopy (KPFM) allowing direct inspection of the work function distribution across the surface with high spatial resolution [16]. The possible secondary phases would result in an apparent variation of electronic structure and work function.…”

Optical, Dielectric and Magnetic Properties of La_1-xNd_xFeO₃ Powders and Ceramics

“…AFM was done using commercial scanning probe microscope Ntegra Aura (NT-MDT Spectral Instruments, Russia) by Budget Sensors ElectriTap300-G tips with the curvature less 25 nm, resonance frequency about 300 kHz, and 20 N/m force constant. In order to clarify chemical homogeneity at the local scale we used Kelvin probe force microscopy (KPFM) allowing direct inspection of the work function distribution across the surface with high spatial resolution [16]. The possible secondary phases would result in an apparent variation of electronic structure and work function.…”

Directed nanoscale metal deposition by the local perturbation of charge screening at the solid–liquid interface

“…[20][21][22] In general, effects of the structure and dynamics of the electrical double layer (EDL) at the solid-liquid interface on nanoscale electrochemistry are not fully understood. 23,24 In the past years, several groups have focused on using SPM techniques to probe the solid-liquid interface, [25][26][27][28][29][30][31][32] in terms of specific adsorption, 33 charge density, and screening. 34,35 In all these studies, care was taken to ensure minimal perturbation of the EDL by the probing tip.…”