Tóm tắt

An a-IGZO based dual gate ion sensitive field effect transistor (DG ISFET) was fabricated utilizing a simple andrncost effective method. Sputtered Al2O3 was used as the top gate dielectric to obtain a greater surface site densityrnand thus a higher sensitivity due to higher surface roughness. Deteriorated characteristics of the bottom gate thinrnfilm transistor (BG TFT) caused by deposition of Al2O3, attributed to the induced oxygen vacancies at the Al2O3/rna-IGZO interface were recovered by optimized annealing at 350 �C in presence of oxygen. The increased value ofrnthe OFF current (~nA) in the BG TFT upon exposure to the electrolyte (pH-4), was attributed to the formation ofrndouble channels in the active (a-IGZO) layer. The conduction in the channel formed at the Al2O3/a-IGZOrninterface dominated over the bottom gate channel (a-IGZO/SiO2 interface) in the turn OFF region while beingrncomparable in the turn ON region. The fabricated DG ISFET showed ~6-fold enhancement in pH sensitivityrn(347.6 mV/pH) from the Nernst’s limit (59 mV/pH). To validate the experimental findings, a T-CAD basedrnsimulation model was proposed by incorporating three dielectric layers to represent the electric double layerrnformed at the electrolyte/insulator interface and at the reference electrode