Paper SS2-TuA1
The Functionalization of Semiconductor Surfaces with Hemin

Tuesday, November 10, 2009, 2:00 pm, Room M

Herein, we present and discuss the semiconductor surface and interface chemistry involved in the chemisorption of hemin on III-V surfaces including InP, GaAs, GaN and on group-IV semiconductors including SiC and Si.

The peculiarity of our study is the use of spectroscopic ellipsometry for the monitoring of surface coverage and interface phenomena. Ellipsometry data are corroborated by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and electrical force microscopy. We discuss the dependence of semiconductor surface treatments e.g. native oxide, chemical treatments, passivating processes whose role is pre-conditioning the surface with –H or –NH terminal groups) on the self-assembling of the functionalizing biomolecules, and of the concentration of the hemin solution and chemistry duration on the chemistry and kinetics of the various semiconductor functionalization. We report also on the effect of benzoic acid addition to the hemin solution as a spacer to prevent formation of hemin aggregates in favor of normal-to-surface hemin orientation. By investigating a number of semiconductor base systems with a gap ranging in a broad range from 0.4 eV (InAs) to 3.4 eV (GaN) we demonstrate for the first time the correlation existing between the sensing activity and the semiconductor gap. This correlation might be useful to choose the appropriate semiconductor-based platform for a target sensing application. A correlation between the band gap of the semiconductors, the surface binding sites and the efficacy of functionalization is established and discussed. .

This work is supported by the 7FP European Project NanoCharM (Multifunctional NanoMaterial Characterization exploiting ellipsometry and polarimetry)