Theoretical, experimental and numerical scanning probe methodologies for high-resolution surface potential determination of clay particles

The determination of the clay particle surface electrostatic potential is of fundamental importance since it governs the electric force exerted at the clay particle/environment interface which in turn affects, for example, liquid/surface interactions, rheology and organic matter self-assembly and adhesion. Because of the confinement of the electrostatic interactions and of the small size of clay particles, nanoscale resolved methodologies are required to investigate their surfaces. Recent developments of Scanning Probe Microscopy (SPM) have widened the spectrum of possible investigations beyond nanotopography, that can be performed at a nanometric level on the surface of single clay particles. Electric Force Microscopy (EFM), Kelvin Probe Force Microscopy (KPFM) and Multimode EFM (MM-EFM) have been developed for surface potential determination. This paper reports on both a theoretical and an experimental approach based on EFM, KPFM and MM-EFM observations of layer silicate surfaces typical of clays

3D finite element analysis of electrostatic deflection of commercial and FIB-modified cantilevers for electric and Kelvin force microscopy: I. Triangular shaped cantilevers with symmetric pyramidal tips

The investigation of the nanoscale distribution of electrostatic forces on material surfaces is of paramount importance for the development of nanotechnology, since these confined forces govern many physical processes on which a large number of technological applications are based. For instance, electric force microscopy (EFM) and micro-electro-mechanical-systems (MEMS) are technologies based on an electrostatic interaction between a cantilever and a specimen. In the present work we report on a 3D finite element analysis of the electrostatic deflection of cantilevers for electric and Kelvin force microscopy. A commercial triangular shaped cantilever with a symmetric pyramidal tip was modelled. In addition, the cantilever was modified by a focused ion beam (FIB) in order to reduce its parasitic electrostatic force, and its behaviour was studied by computation analysis. 3D modelling of the electrostatic deflection was realized by using a multiphysics finite element analysis software and it was applied to the real geometry of the cantilevers and probes obtained by using basic CAD tools. The results of the modelling are in good agreement with experimental data

3D finite element analysis of electrostatic deflection and shielding of commercial and FIB-modified cantilevers for electric and Kelvin force microscopy: II. Rectangular shaped cantilevers with asymmetric pyramidal tips

This paper deals with an application of 3D finite element analysis to the electrostatic interaction between (i) a commercial rectangular shaped cantilever (with an integrated anisotropic pyramidal tip) and a conductive sample, when a voltage difference is applied between them, and (ii) a focused ion beam (FIB) modified cantilever in order to realize a probe with reduced parasitic electrostatic force. The 3D modelling of their electrostatic deflection was realized by using multiphysics finite element analysis software and applied to the real geometry of the cantilevers and probes as used in conventional electric and Kelvin force microscopy to evaluate the contribution of the various part of a cantilever to the total force, and derive practical criteria to optimize the probe performances. We report also on the simulation of electrostatic shielding of nanometric features, in order to quantitatively evaluate an alternative way of reducing the systematic error caused by the cantilever-to-sample capacitive coupling. Finally, a quantitative comparison between the performances of rectangular and triangular cantilevers (part I of this work) is reported

Electrostatic 3D finite element analysis for electric and Kelvin force microscopy

The study of a surface\u2019s electrical properties at very small scales with scanning probe microscopy is of great interest in many theoretical and applicative science fields. For instance, electric and Kelvin probe force microscopy can provide direct information about local polarization, charge distribution, and electrostatic properties of materials surfaces. In semiconductor devices and biological samples, the knowledge of the local electric potential distribution is of significant interest because it helps in linking the specimen\u2019s observed function with its local structure and composition. The understanding of electrostatic forces is, in general, of fundamental importance for the development of nanotechnology, since these forces govern many physical processes on which a large number of technological applications are based