An Electrolyte Gated Carbon Nanotube Field-Effect Transistor Device

Abstract

This thesis describes the preparation of ultrathin films of single walled carbon nanotubes (SWCNT) and their application in a quasi field-effect transistor (FET) configuration. Like other SWCNT-FET devices that have been reported in the literature, our design has a SWCNT layer serving as the channel which is contacted at each end by gold electrodes that act as source and drain, respectively. However, in our electrolyte-gated (EG) FET layout, there is a novel gate design. The gate is an electrolyte solution that is in direct physical and strongly capacitive electrical contact with the SWCNT channel layer, which distinguishes it from most designs wherein the SWCNT film is separated from the gate electrode by a dielectric film of at least 10 nm. The long-term goal of the research is to develop the EGFET as an electrochemical sensor. Prior EGFET prototypes from our laboratory used thick SWCNT films and showed some chemical sensitivity. The present technological hurdle is the preparation of ultrathin SWCNT films. To this end, we have chemically modified both the SWCNT sidewalls and the glass substrate surfaces thus producing much thinner and more conductive SWCNT films. We also succeeded in employing these films in a set of exploratory EGFET experiments to detect various redox coupling chemicals. It is hoped that similarly produced and configured EGFETs will become the basis of a new type of chemical sensor.