Nanoscale intermittent contact-scanning electrochemical microscopy

Abstract

Contribution to the Festschrift for Allen J. Bard, on the occasion of his 80 th birthday.2 Abstract A major theme in scanning electrochemical microscopy (SECM) is methodology for nanoscale imaging with distance control and positional feedback of the tip. We report the expansion of intermittent contact (IC)-SECM to the nanoscale, using disk-type Pt nanoelectrodes prepared using the laser-puller sealing method. The Pt was exposed using a focused ion beam milling procedure to cut the end of the electrode to a well-defined glass sheath radius, which could also be used to reshape the tips to reduce the size of the glass sheath. This produced nanoelectrodes that were slightly recessed, which was optimal for IC-SECM on the nanoscale, as it served to protect the active part of the tip. A combination of finite element method simulations, steady-state voltammety and scanning electron microscopy, for the measurement of critical dimensions, was used to estimate Pt recession depth. With this knowledge, the tip-substrate alignment could be further estimated by tip approach curve measurements. IC-SECM has been implemented by using a piezo-bender actuator for the detection of damping of the oscillation amplitude of the tip, when IC occurs, which was used as a tip position feedback mechanism. The piezo-bender actuator improves significantly on the performance of our previous setup for IC-SECM, as the force acting on the sample due to the tip is greatly reduced, allowing studies with more delicate tips. The capability of IC-SECM is illustrated with studies of a model electrode (metal/glass) substrate.

Impact of Adsorption on Scanning Electrochemical Microscopy Voltammetry and Implications for Nanogap Measurements

“…[27][28][29][30][31][32][33] When using nanoscale electrochemical systems for quantitative kinetic measurements, precise knowledge of electrode geometry and the physicochemical characteristics of 4 electrochemical cells is imperative. For example, unaccounted for irregularities in the electrode shape from idealized models, 34 tip recession [35][36][37] or 'lagooned' geometries 38,39 may produce highly erroneous determination (overestimation) of ET kinetic parameters. 40 Significant efforts have thus aimed at developing easy and reproducible electrode preparation procedures and better means of geometric characterization.…”

Intermittent‐contact Scanning Electrochemical Microscopy (IC‐SECM) as a Quantitative Probe of Defects in Single Crystal Boron Doped Diamond Electrodes

“…Most recently, we advocated intermittentcontact (IC)-SECM [18][19] for constant tip-substrate separation imaging of electrode activity. IC-SECM modulates the SECM tip position in the direction normal to the substrate surface with a small sinusoidal oscillation applied to the piezoelectric positioner to which the tip is mounted.…”

Combined electrochemical-topographical imaging: a critical review

“…95 A more recent example of this involved arrays of embedded diamond nanoelectrodes, in which an individual 320 nm diameter electrode in an insulating surround was electrochemically resolved in feedback mode, as shown in Fig. 100,101 Nonetheless this technique has enabled surface-tracking and topographical measurement on model and hard surfaces. 96 The topographical measurement here is again limited to tracking the surface roughness of the surround and does not resolve the embedded electrode due to the overall tip size.…”

“…7. [99][100][101][102] Whilst imaging resolution has been predominantly limited to the micron scale, the application of smaller probes has been demonstrated. Mauzeroll and co-workers 72 used similar nanoelectrode probes with a smaller insulating sheath to image 1 mm bands on a rewritable CD in electrochemical feedback mode as shown in Fig.…”