Brown University School of Engineering

Joint Materials/Solid Mechanics Seminar Series “Surface and Growth Stress at Solid Electrodes”

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Monday, November 19, 2012 4:00pm - 5:00pm

Joint Materials/Solid Mechanics Seminar Series “Surface and Growth Stress at Solid Electrodes” Dr. Gery R. Stafford Material Measurement Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899 Abstract: Wafer curvature and cantilever bending techniques have been used by the electrochemical community to examine stress development during electrochemical processing. Surface stress changes as low as 10−3 N/m can typically be resolved from cantilever electrodes immersed in solution and under potential control. Such resolution makes this measurement useful for examining virtually all aspects of electrochemistry; i.e., electrocapillarity, adsorption processes, underpotential deposition, electrodeposition, battery reactions, and metal hydride formation. Often these processes occur either simultaneously or in rapid succession and we are often limited to measuring the influence of the dominant process in the time-scale of the experiment. Electrochemical impedance spectroscopy (EIS) is a technique in which one measures the impedance of an electrochemical system over a range of frequencies, revealing information about the reaction mechanisms: different reaction steps will dominate at frequencies dictated by their relaxation times. Whereas traditional EIS determines the transfer function of the current in response to potential modulation, we are interested in determining the transfer function of the stress (as measured from cantilever curvature) to the same potential modulation. This will provide us with the time constants for the stress response that might enable us to directly link the stress to specific electrochemical phenomena. The first part of this talk will examine surface and growth stress development during the electrochemical deposition of metal monolayers and pseudomorphic thin films, such as Pb, Pd and Pt onto (111)-textured Au cantilever electrodes. The latter two systems are of considerable interest to the catalysis community where elastic strain is known to influence the catalytic properties of a material. The second part of this talk will focus on our efforts to link the electrochemical and mechanical impedance of Au and Pt cantilever electrodes in HClO4 electrolyte. Monday, November 19, 2012 4:00-5:00 pm B&H Room 190