Plasma-Deposited Fluorocarbon Films: Insulation Material for Microelectrodes and Combined Atomic Force Microscopy−Scanning Electrochemical Microscopy Probes

Abstract

Pinhole-free insulation of micro- and nanoelectrodes is the key to successful microelectrochemical experiments performed in vivo or in combination with scanning probe experiments. A novel insulation technique based on fluorocarbon insulation layers deposited from pentafluoroethane (PFE, CF3CHF2) plasmas is presented as a promising electrical insulation approach for microelectrodes and combined atomic force microscopy-scanning electrochemical microscopy (AFM-SECM) probes. The deposition allows reproducible and uniform coating, which is essential for many analytical applications of micro- and nanoelectrodes such as, e.g., in vivo experiments and SECM experiments. Disk-shaped microelectrodes and frame-shaped AFM tip-integrated electrodes have been fabricated by postinsulation focused ion beam (FIB) milling. The thin insulation layer for combined AFM-SECM probes renders this fabrication technique particularly useful for submicro insulation providing radius ratios of the outer insulation versus the disk electrode (RG values) suitable for SECM experiments. Characterization of PFE-insulated AFM-SECM probes will be presented along with combined AFM-SECM approach curves and imaging.

Methods of photoelectrode characterization with high spatial and temporal resolution

“…If variations in the height of sample features are large compared to the tip/substrate gap distance, it becomes very difficult to distinguish differences in UME current caused by topology rather than electrochemical activity. When the desired UME tip/substrate separation distance is comparable to the roughness of the sample surface, several advanced versions of SECM may be employed, including scanning-force microscopy, 64 hybrid SECM/atomic-force microscopy (AFM), 65,66 intermittent-contact SECM, [61][62][63] and electron transfer/ion transfer SECM. 67 Although this section has focused on the implementation of SECM for the analysis of the spatial variation of product formation on photoelectrode surfaces, SECM can also be used to investigate local changes in pH 68 and corrosion processes, [69][70][71][72][73][74] analyze surface coverage of adsorbed intermediates (surface interrogation SECM), [75][76][77][78][79] and measure short-lived intermediates.…”

Combined electrochemical-topographical imaging: a critical review

“…A number of such images have emerged from the Kranz group using the recessed Pt ring probe, 39,46,47 and more recently by extending this conguration to a boron-doped diamond (BDD) ring electrode. A number of such images have emerged from the Kranz group using the recessed Pt ring probe, 39,46,47 and more recently by extending this conguration to a boron-doped diamond (BDD) ring electrode.…”

Fabrication of Scanning Electrochemical Microscopy-Atomic Force Microscopy Probes to Image Surface Topography and Reactivity at the Nanoscale

“…13,19-22 So far, combining AFM with SECM requires customized solutions as limited commercial SECM modules for AFM systems are available and, therefore, the technology only is used by a limited number of researchers. In addition, fabrication of combined probes remains challenging.…”