Space charge at nanoscale: Probing injection and dynamic phenomena under dark/light configurations by using KPFM and C-AFM

Abstract

Fine description of the electrical properties of solids at their surfaces is a very old problem, difficult to tackle because the surface of a solid itself represents a break in the periodic structure of crystallized materials, hence a defect, and most importantly because of the potential impact of surface oxidation, contamination, humidity, atmosphere, etc., on the material response (Galembeck et al. in Polymer 42:4845, 2001 [1]). For dielectrics, electrical charging of the surface leads to the build-up of a surface potential. The occurring mechanisms depend on the kind of charges being deposited, e.g. by triboelectrification, and are particularly difficult to anticipate (Lacks and Sankaran in J Phys D Appl Phys 44:453001, 2001 [2], Shinbrot et al. in Phys Rev E 96:032912, 2017 [3]). Aside these difficulties in defining the surface properties, nanosciences and nanomaterials have brought us new paradigms with the tremendous increase of the amount of interfaces between particles and host matrix, and with the variety in the material nature and interface linked to the different elaboration processes. In a way it may constitute a chance to better describe what interfaces on an electronic properties standpoint are, because materials are better controlled. Besides the nanostructuration of materials, the miniaturization of devices is a further challenge to face. When dealing with thin layers (thicknesses of less than 100 nm) the rules for bulk properties behavior are broken. Obviously, in both cases the experimental approach is more demanding, since the tools that are implemented for the study must have a spatial resolution compatible with the scale at which phenomena should be probed. In this Chapter we illustrate on a few examples the need for ever lower scale characterization of the electrical properties of dielectric materials.