Well-established materials in microelectronic devices systems for differential-mode extended-gate field effect transistor chemical sensors

Abstract

Well-established materials commonly used in microfabrication industry were studied as chemical sensing elements of extended gate field effect transistor (EGFET) chemical sensors. Microelectronic components were used in the differential mode of operation. Three differential pairs of films made of polyaniline (protonated and non-protonated), fluorine doped tin oxide and titanium dioxide were used: PANI-EB×PANI-ES, PANI-EB×FTO and FTO×TiO2. Good linearity was observed for all cases in the pH range 3 to 8. The differential measurements were also performed as a function of: i) temperature in the range 30°C to 50°C, ii) buffer concentration from 1mM to 400mM, and iii) time, for three hours. Hysteresis measurements for the 5-2-5-8-5pH loop cycle were also conducted. The pair composed of polyaniline in the protonated and non-protonated form presented the best results with a sensitivity of 37±4mV/pH, good linearity, and stable response against variation of temperature and buffer concentration. A similarity in ion-sensing mechanisms and electrical properties of the single films is necessary for the fabrication of good and stable differential sensors as will be discussed. These materials can be satisfactorily used in miniaturized electronic sensor systems, thus promising great advances in the field.