scanning electrochemical microscopy

[...]... University of Leipzig, Leipzig, Germany 1 INTRODUCTION AND PRINCIPLES Allen J Bard The University of Texas at Austin Austin, Texas I BACKGROUND OF SCANNING ELECTROCHEMICAL MICROSCOPY This volume is devoted to a complete and up-to-date treatment of scanning electrochemical microscopy (SECM) In this introductory chapter, we cover the historical background of the technique, the basic principles of SECM, and an... 23 24 25 26 27 28 29 30 31 32 33 34 35 36 2 INSTRUMENTATION David O Wipf Mississippi State University Mississippi State, Mississippi I INTRODUCTION A scanning electrochemical microscope is a scanning probe microscope (SPM) The scanning electrochemical microscopy (SECM) instrument necessarily resembles other SPM instruments, but differences in the probe tip and signal lead to differences in design and... the electrochemical response of the tip, and this perturbation provides information about the nature and properties of the substrate The development of SECM depended on previous work on the use of ultramicroelectrodes in electrochemistry and the application of piezoelectric elements to position a tip, as in scanning tunneling microscopy (STM) Certain aspects of SECM behavior also have analogies in electrochemical. .. blockage of diffusion of O to the tip by the substrate, there is also the oxidation of the product R back to O This O generated at the Introduction and Principles 5 FIG 3 Basic principles of scanning electrochemical microscopy (SECM): (A) far from the substrate, diffusion leads to a steady-state current, iT,ϱ; (B) near a conductive substrate, feedback diffusion leads to iT > iT,ϱ; (C) near an insulating... semiconductors can be etched or metals deposited on a surface by passing the tip close to the surface and carrying out an appropriate electrochemical reaction Two different modes are possible In the direct Introduction and Principles 9 mode, the tip acts as the counterelectrode and the desired electrochemical reaction occurs on the substrate For example, Cu can be etched from a Cu substrate Spatial resolution is... number of reviews (17–21) A simplified experimental setup for an electrochemical experiment is shown in Figure 1 The solution contains a species, O, at a concentration, c, and usually contains supporting electrolyte to decrease the solution resistance and insure that transport of O to the electrode occurs predominantly by diffusion The electrochemical cell also contains an auxiliary electrode that completes... can also be employed and is used in studies of reactions at a substrate surface (Chapters 6, 9, 11, and 12) The SG/TC mode was first used to study concentration profiles near an electrode surface without scanning and imaging (11–13) The most frequent mode of operation of the SECM is the feedback mode, where only the tip current is monitored As discussed in the next section, the tip current is perturbed... Bard curve is produced The current eventually limits to a value that is completely controlled by the rate of mass transfer by diffusion of O from the bulk solution to the electrode surface, where the electrochemical reaction has decreased its concentration to essentially zero For a conductive disk of radius a in an insulating sheath, this steady-state diffusion-controlled current when the tip is far... illustrate a wide range of applications of SECM that have appeared Given below is an overview and some examples that might help put the technique in perspective before the detailed treatments A Imaging By scanning the tip in the x-y plane and measuring current changes (the constant height mode) (or, less frequently, by maintaining a constant current and measuring the changes in d in a constant current mode),... surfaces that have active and passive sites B Ultramicroelectrode Shape Characterization It is frequently difficult to determine the actual shape of an ultramicroelectrode by examination using an optical or scanning electron microscope For example, the conducting portion may be slightly recessed inside the glass mantle, or the shape may be that of a cone protruding from the insulator Electrodes with radii . Austin Austin, Texas I. BACKGROUND OF SCANNING ELECTROCHEMICAL MICROSCOPY This volume is devoted to a complete and up-to-date treatment of scanning electrochemical microscopy (SECM). In this introductory. iii Contributors ix 1 INTRODUCTION AND PRINCIPLES 1 Allen J. Bard I. Background of Scanning Electrochemical Microscopy 1 II. Principles of SECM 2 III. Applications of SECM 9 References 15 2 INSTRUMENTATION. SECM 59 Appendix; Suppliers 66 References 71 vi Contents 3 THE PREPARATION OF TIPS FOR SCANNING ELECTROCHEMICAL MICROSCOPY 75 Fu-Ren F. Fan and Christophe Demaille I. Introduction 75 II. Preparation