Charge migration on hydrophobic and hydrophilic silicon dioxide

Experimental results are presented which shed light on the properties of th in discontinuous metal films as chemical sensing elements. They demonstrate further some interesting differences between hydrophilic and hydrophobic s ensing structures. Two different methods are used to study the migration of charges out onto the oxide surface outside the metal gate of metal-oxide-s emiconductor capacitors after treatment of the surface with hydrochloric ac id. The charge migration is observed tither as a time dependent increase of the inversion capacitance or as a possibility to generate a photocapacitiv e current by a chopped light beam hitting the oxide surface at a distance f rom the contact. It is concluded that the charge migration occurs only if t he surface was hydrophilic before the HCl-treatment. For a hydrophobic surf ace neither the inversion capacitance nor the photocapacitive current chang ed upon ion-treatment, An explanation for an observed increase of the capac itance level of hydrophilic structures immnersed in electrolytes is also gi ven. (C) 1999 Elsevier Science S.A. All rights reserved.