Film thickness dependence of glucose response for spin-coated zinc oxide-based non-enzymatic glucose sensor

Zinc oxide (ZnO) thin films were deposited on indium tin oxide (ITO) substrates by spin coating method to be applied as sensing membrane of an extended gate field effect transistor (EGFET) glucose sensor. This paper focused on the effect of film thickness to the glucose sensing characteristics. The surface morphology of the thin films were characterized using Field Emission Scanning Electron Microscopy (FESEM). FESEM images revealed that the thin films became denser and the grain size increasing proportional with the thickness while the sensing properties measured by Extended-gate Field Effect Transistor (EGFET) measurement setup indicated that the sensitivity decreased as the thickness increased. From the I-V measurement, we found that the conductivity increased with the increasing thickness. Based on the results, we propose that there is a relation between the conductivity and the sensor sensitivity.