Biological Applications

Electrolyte-oxide-semiconductor (EOS) capacitors were fabricated to elucidate; (a) the dynamics of the ionic double layer under field-effect modulation, (b) the effect of electrolyte composition on the zero-field voltage, and (c) the role of insulator surface groups on the differential capacitance of the fluidic double layer. Surface groups, owing to their amphoteric nature, are known to regulate charge when a potential is applied, which in turn sets up the double layer at the solid-electrolyte surface [1]. Through this study, we show a complex interplay between double layer dynamics, ionic composition and surface groups through capacitance-voltage measurements. Valency of the cationic species was shown to result in a strong hysteretic effect dependent on surface charge density. Varying time intervals during the cyclic sweep indicated the dynamics of ionic adsorption/desorption effects. The potential of hydrogen (pH) dependence was shown to exhibit near-Nernstian sensitivity. The pH response increased for increase in surface charge density, indicating that ionic adsorption might play the additional role in determining the zero-field potential.