Numerical Simulation of Scanning Electrochemical Microscopy Experiments with Frame-Shaped Integrated Atomic Force Microscopy−SECM Probes Using the Boundary Element Method

Abstract

Integrated submicroelectrodes for combined AFM-SECM measurements are characterized with numerical simulations using the boundary element method. SECM approach curves and SECM images are calculated and analyzed for a model substrate containing pronounced topographical and electrochemical features. The theoretically calculated image has been compared to the experimental data and shows excellent quantitative agreement. Hence, the applicability of integrated AFM-SECM electrodes for combined electrochemical and topographical imaging and a profound theoretical description including quantification of the obtained results are demonstrated.

Simple and Clear Evidence for Positive Feedback Limitation by Bipolar Behavior during Scanning Electrochemical Microscopy of Unbiased Conductors

“…1,4,7 However, because of the inequality in eq 5, in the present system, the fulfillment of this fact implies that r hole /r tip is large enough compared to (Δi recycl ) lim = (π/4)r tip /l as follows from eq 2. However, since r hole /r tip is fixed by the system construction while (Δi recycl ) lim increases drastically when l f 0, the inequality in eq 5 dictates that, as soon as L < L min = (π/4)Â r tip /r hole , Δi recycl is necessarily limited by the performance of the remote disk rather than by the electrochemical properties of the probed one.…”

“…Whenever the substrate may perform as a perfect collector, 6 at tipÀsubstrate distances, l, small enough for I nf to be negligible, 1,4,7 I tip is expected to tend toward the current value observed in the thin-layer cell composed by the two facing electrodes. If the substrate is much wider than the tip, this limiting value should be controlled only by the tip surface area and the tipÀsubstrate distance.…”

“…At the steady state, the scanned disk of the substrate then probes a solution enriched with Red and may then perform as an anode (viz., oxidizing Red back into Ox). 1,4,5,7,11 However, the corresponding oxidation current, ÀΔi recycl , needs to be compensated by a cathodic one (viz., þ Δi recycl ) which can be delivered only by means of Ox reduction. 4,5 When the tipÀsubstrate distance L is sufficiently small for no significant Ox concentration to be present at the surface of the scanned disk, 7 the cathodic pole may only consist of the remote substrate disk which is exposed to the Ox bulk solution.…”

“…4,5 When the substrate is a large nonresistive conductor, this is not a problem and the recycling rate is regulated only by the electrochemical cross-talk between the tip and the substrate area it is probing. 4,6,7 Since this is the case in most usual circumstances, this characteristic is often extrapolated to conducting substrates of any size, thus leading to a misguided but commonly used view. Indeed, when the substrate is highly resistive (e.g., when composed of poorly connected small metallic grains or elements 4c,e or of a resistive organic film, 2c,d etc.)…”

Soft Microelectrode Linear Array for Scanning Electrochemical Microscopy

“…20,21 For a rather long time, instrumental developments have aimed at increasing the lateral resolution and providing complementary information such as topography and local reactivity from complex samples. For instance, combination of the SECM principle with atomic force microscopy (AFM) [22][23][24][25][26][27][28][29][30][31][32] …”