Interpretation of atomic force microscope (AFM) signals from surface charge on insulators

Abstract

Charge stored on the surface of an insulator at the sub-micron length scale can be observed with an atomic force microscope (AFM). The dynamics of the charge spreading due to three mechanisms are calculated: (a) surface conduction; (b) surface charge spreading due to self-repulsion; and (c) bulk space charge motion, which is necessarily coupled to a surface charge. Self-similar motion occurs in all three cases. The AFM signals decay with time, and the shapes of the decay curves are similar. We show that the surface-charge-perturbed cases can be identified because the time constant depends on the magnitude of the initial charge, but that separating the pure surface spreading from the bulk process may prove difficult.

Experimental characterisation of charge distribution and transport in electron irradiated PMMA

“…There is now a considerable amount of literature concerned with experimental characterization of space charge [6][7][8][9] and with phenomenological models of space charge formation and discharge [10]. However space charge accumulation and discharge together with related trapping-detrapping phenomena are still relevant.…”

Analysis of the scanning electron microscope mirror method for studying space charge in insulators

“…Since electrostatic forces are much larger than atomic forces, the AFM must be operated at a reduced resolution of about 1 m, and is restricted to charges in the 1 fC range, 1 but it is well suited to dynamic studies. 2 The SEM also has a resolution in the 1 m range, and the magnitude of the charge observed is typically 10 pC. With minor exceptions, it is restricted to charge distributions that are negative overall, which are usually implanted by using the SEM itself.…”

Charge trapping behavior visualization of dumbbell-shaped DSFXPY via electrical force microscopy

“…These indicate that the electrons or holes can be trapped in the localized region of the DSFXPY film by applying the controllable biases on the conductive AFM tip. In general, the trapped charges in the films will generate a divergent electric field to drive the charges to horizontal and vertical directions of the sample surface, 30 thus, the deposited charges are probably trapped in the DSFXPY film and/or at the interface of DSFXPY and SiO 2 .…”