Recent results on self-organized silicon nanostructure formation by electrochemical conditioning will be presented. Based on silicon (photo)electrochemical processing in alkaline and acidic electrolytes, formation of step-bunched surfaces and generation of nanopore patterns in silicon oxide during current oscillations are described. Metal electrodeposition into oxide nanopores is shown to result in a photoactive nanostructure that operates in the photovoltaic and in the photoelectrocatalytic mode. Pore patterns and spatially selective Pt electrodeposition are analyzed by HRSEM, AFM and XPS where the latter is used for metal identification. Device improvement strategies will be discussed.
Detailed analyses of step-bunched surfaces employing SRPES (employing a combined electrochemistry-UHV surface analysis system) will be presented. In combination with AFM measurements, assessment of the governing dissolution mechanism in alkaline solution becomes possible. XPS valence band spectroscopy and SRPES show the presence of an accumulation layer that is confirmed by Kelvin-Probe atomic force microscopy (KPFM) where an inhomogeneous lateral distribution of the electrostatic potential across the surface is observed. In a novel application, AFM images of the site-specific adsorption of proteins on the step bunched surface where the semiconductor accumulation condition is most pronounced will be presented and discussed.