Sensitivity Enhancement Mechanisms in Textured Dielectric based Electrolyte-Insulator-Semiconductor (EIS) Sensors

Abstract

The possible mechanisms governing the enhancement of sensitivities of Electrolyte-insulator-semiconductor (EIS) devices upon surface modification (texturing) realized by electrostatic attachment of silica particles using 3-aminopropyl triethoxysilane (APTES) as a linker are presented. EIS devices were fabricated with a textured dielectric surface using SiO2 particles (of diameters 475, 135, and 70 nm) and screen printed Ag/AgCl electrodes. A maximum pH sensitivity of 52.4 mV/pH was achieved for the EIS device textured with 70 nm particle size while the sensitivity with the planar dielectric was 37.1 mV/pH. The APTES modification enhanced the adsorption of H+ ions by protonation of the –NH2 to –NH3+ sites as seen from the capacitance versus voltage (C-V) hysteresis voltages. UV-Vis absorption and photoluminescence (PL) spectra indicated that the surface defects on the textured surface increased with decreasing particle size. Zeta potential measurements suggested a combined acid-base behavior of textured surface with the formation of –NH3+ and −Si-O− groups. The flatband voltage study showed that surface textured with 70 nm SiO2 particles provided the optimum ratio of Si-OH and –NH2 groups. The various chemical treatments during texturization did not affect the characteristics at the Si/SiO2 interface.