AVS 53rd International Symposium
    Thin Film Monday Sessions
       Session TF-MoA

Paper TF-MoA5
Fabrication of Integrated Scanning Electrochemical-Atomic Force Microscopy Probes by Atomic Layer Deposition of Aluminum Oxide

Monday, November 13, 2006, 3:20 pm, Room 2022

Session: ALD and Applications II
Presenter: D.J. Comstock, Northwestern University
Authors: D.J. Comstock, Northwestern University
M.C. Hersam, Northwestern University
J.W. Elam, Argonne National Laboratory
M.J. Pellin, Argonne National Laboratory
Correspondent: Click to Email
Integrated scanning electrochemical-atomic force microscopy (SECM-AFM) is a powerful tool for characterizing electrochemical and biological processes ranging from corrosion to membrane transport. SECM-AFM utilizes probes consisting of a tip electrode integrated onto a conventional atomic force microscopy cantilever, allowing for simultaneous but independent topographic and electrochemical imaging. In this study, we describe a novel process for fabricating integrated SECM-AFM probes using atomic layer deposition (ALD) techniques. ALD allows for the deposition of highly conformal, continuous insulating films with precise thickness control and is thus well suited for this project. Fabrication starts with commercially available conductive AFM probes, onto which a 50 nm thick aluminum oxide film is deposited by ALD. This insulating film serves to encapsulate the probe body, cantilever, and tip and eliminate electrical leakage currents when operating in an electrochemical environment. The tip nanoelectrode is fabricated using focused ion beam milling to selectively remove aluminum oxide from the tip apex and expose the underlying conductive film. The integrated probes are characterized by scanning electron microscopy (SEM) throughout fabrication to determine both the quality and morphology of the insulating film and the dimensions of the electrode. The films and fabricated probes are electrochemically characterized by cyclic voltammetry, in which the diffusion-limited redox current is used to determine the area of the exposed nanoelectrode. In addition, silver electrodeposition is used to visually confirm that the electrochemical activity of the probe is limited solely to the nanoelectrode at the tip apex. Both SEM imaging and electrochemical characterization have revealed tip electrodes with diameters as small as 50 nm. Finally, we demonstrate the application of these probes to SECM-AFM by acquiring topographic and electrochemical images of a model substrate.