Abstract
Phase-mode electrostatic force microscopy (EFM-Phase) is a viable technique to image surface electrostatic potential of silicon oxide stripes fabricated by oxidation scanning probe lithography, exhibiting an inhomogeneous distribution of localized charges trapped within the stripes during the electrochemical reaction. We show here that these nanopatterns are useful benchmark samples for assessing the spatial/voltage resolution of EFM-phase. To quantitatively extract the relevant observables, we developed and applied an analytical model of the electrostatic interactions in which the tip and the surface are modelled in a prolate spheroidal coordinates system, fitting accurately experimental data. A lateral resolution of ∼60 nm, which is comparable to the lateral resolution of EFM experiments reported in the literature, and a charge resolution of ∼20 electrons are achieved. This electrostatic analysis evidences the presence of a bimodal population of trapped charges in the nanopatterned stripes.
Highlights
Organic conductors and semiconductors are widely accepted as ideal materials to develop the generation of electrophysiological sensing devices [1,2,3,4]
The goal of this study was to demonstrate the two-fold role of the electrical double-layer (EDL) resistance on the quality of the recorded bioelectrical signal
The noise of the PEDOT:PSS electrode is one order of magnitude lower than that noise generated by the gold electrode
Summary
Organic conductors and semiconductors are widely accepted as ideal materials to develop the generation of electrophysiological sensing devices [1,2,3,4]. A number of studies in the literature have demonstrated the superior performance of organic semiconductors when incorporated into structures, such as simple electrodes or transistors [11], to record bioelectrical signals from electrogenic cells, like neurons [6,12,13] and cardiomyocytes [14,15,16] and even for in vivo recordings [17,18]. The good electrical performance of organic-based devices is partly due to the low interfacial impedance, when in contact with liquids. In particular, poly(3,4ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), have an extremely high capacitance. Rivnay et al [19] showed for the first time the intriguing feature that the capacitance in PEDOT:PSS films scales
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