Batch Fabrication of Atomic Force Microscopy Probes with Recessed Integrated Ring Microelectrodes at a Wafer Level

Abstract

A batch fabrication process at the wafer-level integrating ring microelectrodes into atomic force microscopy (AFM) tips is presented. The fabrication process results in bifunctional scanning probes combining atomic force microscopy with scanning electrochemical microscopy (AFM-SECM) with a ring microelectrode integrated at a defined distance above the apex of the AFM tip. Silicon carbide is used as AFM tip material, resulting in reduced mechanical tip wear for extended usage. The presented approach for the probe fabrication is based on batch processing using standard microfabrication techniques, which provides bifunctional scanning probes at a wafer scale and at low cost. Additional benefits of batch fabrication include the high processing reproducibility, uniformity, and tuning of the physical properties of the cantilever for optimized AFM dynamic mode operation. The performance of batch-fabricated bifunctional probes was demonstrated by simultaneous imaging micropatterned platinum structures at a silicon dioxide substrate in intermittent (dynamic) and contact mode, respectively, and feedback mode SECM. In both, intermittent and contact mode, the bifunctional probes provided reliable correlated electrochemical and topographical data. In addition, simulations of the diffusion-limited steady-state currents at the integrated electrode using finite element methods were performed for characterizing the developed probes.

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 range of probe geometries have been implemented, including nanowires, 26 needles, 27,28 pyramidal 29 and conical probes, [30][31][32][33] as well as alternative approaches to the recessed electrode conguration. 30,31,33,[38][39][40] Despite the breadth of literature surrounding SECM-AFM, there have been relatively few examples in which electrochemical-topographical imaging has been demonstrated. Whilst many of these approaches are only suited to serial probe-by-probe production or modication of existing AFM probe architectures, a number of waferlevel methods adopting microprocessing technologies have enabled batch production.…”

“…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.…”

Local Imaging of an Electrochemical Active/Inactive Region on a Conductive Carbon Surface by Using Scanning Electrochemical Microscopy

“…This SECM technique could also image other chemical functionalities, such as that of fluorine, which exhibits an extremely slow electron transfer rate for Fe 2+/3+ and Fe(CN)6 3-/4-on a carbon substrate. By using highresolution SECM techniques, 20,27,28 these surface states derived on the electrode could be imaged with sub mm lateral resolution.…”