Electrochemical passivation of gallium arsenide surface with organic self-assembled monolayers in aqueous electrolytes

Self-assembled monolayers of octadecylthiol (ODT) were reconstituted on fre shly etched gallium arsenide (n-GaAs) for the electrochemical stabilization against decomposition of the surfaces (passivation) in aqueous buffers. Th e surface composition was evaluated by x-ray photoelectron spectroscopy to optimize the surface treatment before ODT deposition. Electrochemical prope rties of the monolayers were monitored by cyclic voltammetry and impedance spectroscopy. The impedance spectrum of the photoetched n-GaAs after the de position of the ODT monolayer was stable in an aqueous electrolyte at pH=7. 5 for more than 24 h within the sensitivity of our experimental technique. The effective passivation of GaAs surfaces is an essential step towards bio sensor applications. (C) 2000 American Institute of Physics. [S0003-6951(00 )01422-4].