Diode characteristic of electrolyte-oxide-semiconductor structure for potential chemical and biological applications

This paper reports an abnormal diode characteristic of electrolyte-oxide-semiconductor (EOS) structure. The EOS structure is made up of an n-type silicon layer, a low-pressure-chemical-vapor-deposition SiO₂ layer and an electrolyte-solution layer, from bottom to top. It shows a stable one-way electrical conductivity when external voltages are applied between the electrolyte-solution and silicon layers. Nanopillar forests are employed in the structure to improve the forward-current value. The EOS structures with different cross-sectional areas and different electrolyte-solutions e.g. in concentrations and pH values are tested, illustrating this kind of half-nanofluidic diodes has a great potential for chemical and biological applications.

1. INTRODUCTION

Electrolyte-insulator-semiconductor (EIS) structure first appeared in the ion-sensitive field-effect transistors proposed by Bergveld [1]. Afterward, electrolyte-insulator-semiconductor field-effect transistor (EISFET) was put forward by C. D. Fung et al. [2] [3], using the EIS structure as a key part of the device. Due to the electrochemical properties of the insulator layer, the EISFETs are widely used for measuring pH values and other ions in electrolytes, or as chemical and biosensors [4], and many complicated EIS structures were studied.