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Thurs., March 4, 2010, 1p.m.
NSERL 3.204














“Metal-ion Supported (Photo)electrochemical Surface Conditioning of Silicon for Photoelectrocatalytic Hydrogen Production”
Dr. Michael Lublow, Helmholtz Zentrum Berlin

In a novel approach, metal-ion additions to etching and oxidizing solutions are exploited to preserve the conductivity of micro- and nanoporous silicon overlayers and to produce nanoscaled metal-oxide-semiconductor contacts. Using Au, Ag or Au-Ag mixtures, these metal-contacts give additionally rise to localized plasmonic resonances under visible light illumination as monitored by reflectance measurements of p-polarized light near Brewster’s angle of the substrate. Employing XPS/UPS photoelectron emission spectroscopy, scanning electron microscopy and UV/VIS reflectometry, chemical and electronic, structural and optical properties of the respective interfaces upon metal-ion variation are investigated. The findings are furthermore compared to first results obtained on GaAs, InP and GaN. For application in the field of photoelectrocatalytic production of hydrogen, two silicon-based devices are presented that benefit from 1) the properties of conductive planar black nanoporous layers and 2) plasmonic resonances of combined micro- and nanostructured interfaces, excited by light of arbitrary polarization/angle of incidence. For fabrication of the latter, device efficiencies and optical properties after self-organized electrochemical surface modification are compared to those after microfabrication by e-beam lithography and UV photolithography.

The presentation will start with a brief overview of current activities at the HZB Institute of Solar Fuels and Energy Storage Materials in the field of (photo)electrocatalytic water-splitting.

Michael Lublow has been employed at the Helmholtz center since 1997. His current work comprises micro- and nanostructure formation at silicon interfaces (funded by the German Research Foundation) and, since 2010, contributions to H2-fuel generation at semiconductor nanoarchitectures (funded by the Federal Ministry for Education and Research). He was active in the technology transfer of advanced optical methods and is supervising graduate and doctoral students in the field of electrochemistry, optics and scanning probe microscopy. His primary research interests are chemical and topographical modification of semiconductor interfaces, in situ application of optical methods, preparation of plasmonically active photoelectrodes and mathematical modeling.