Structural characterization of GaAs/thiol/electrolyte interface

The present work is motivated by attempts in our laboratory to develop the physical basis for the design of biosensors (suited for aqueous medium) bas ed on biofunctional supported membranes. We studied the electrical properti es of n-doped gallium arsenide (GaAs) in contact with electrolyte and the h igh insulating properties of self-assembled monolayers (SAMs) of octadecane thiol (C18H37SH) by impedance spectroscopy and cyclic voltammetry. The aver age thickness of the thiol monolayer was measured by ellipsometry and confi rmed by impedance. The analysis of the impedance in terms of equivalent cir cuits of the GaAs/electrolyte and GaAs/insurator/electrolyte interface is d iscussed. This analysis allowed measurements of the defect area fraction of the thiol monolayer. (C) 2000 Elsevier Science B.V. All rights reserved.