Nanoscale thickness double-gated field effect silicon sensors for sensitive pH detection in fluid

Oguz H. Elibol, Purdue University - Main Campus
Bobby Reddy Jr., Micro and Nanotechnology Laboratory and Department of Electrical and Computer Engineering, University of Illinois
Rashid Bashir, Birck Nanotechnology Center and Bindley Bioscience Center, Purdue University

Abstract

In this work, we report on the optimization of a double-gate silicon-on-insulator field effect device operation to maximize pH sensitivity. The operating point can be fine tuned by independently biasing the fluid and the back gate of the device. Choosing the bias points such that device is nearly depleted results in an exponential current response-in our case, 0.70 decade per unit change in pH. This value is comparable to results obtained with devices that have been further scaled in width, reported at the forefront of the field, and close to the ideal value of 1 decade/pH. By using a thin active area, sensitivity is increased due to increased coupling between the two conducting surfaces of the devices.