AVS 50th International Symposium
    Nanometer Structures Tuesday Sessions
       Session NS-TuP

Paper NS-TuP5
Formation of Nanoporous Noble Metal Films by Electrochemical Dealloying of PtxSi1-x

Tuesday, November 4, 2003, 5:30 pm, Room Hall A-C

Session: Poster Session
Presenter: J.C. Thorp, Arizona State University
Authors: J.C. Thorp, Arizona State University
K. Sieradzki, Arizona State University
N. Dimitrov, Arizona State University
S.T. Picraux, Arizona State University
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Electrochemical dealloying of metallic alloy mixtures provides a novel way to form nanoporous structures. In the present study we demonstrate the extension of this concept to metal-silicon alloys on silicon platforms for PtxSi1-x. The PtxSi1-x (x = 50 and 25%) alloys are formed by deposition and thermal treatment. Thermal reaction of Pt films is used to form PtSi silicide layers and co-deposition for more silicon rich alloys. The films (200 to 800 nm thick) are then dealloyed in concentrated HF by an electrochemical process that leaches out the silicon. Anodic polarization curves are used to establish the optimum potential for dealloying, for example near + 400 mV (SCE) for PtSi with current densities of approximately 10 mA/cm2. Rutherford Backscattering Spectrometry (RBS) demonstrates the formation of a pure Pt layer on the metal silicide layer as dealloying process progresses and thus provides a direct observation of the dealloying kinetics. The resulting morphology of the nanoporous noble metal structures is determined by scanning electron microscopy. Results are presented for various Pt silicon alloys and dealloying conditions, and preliminary results will be discussed for Au silicon alloys. These nanoporous noble metal thin film structures provide high surface area electrodes on Si. Such nanostructures are of interest for microscale electrochemical sensing and microfuel cells.