Fig. 1
Wafer-scale fabrication and electrical properties of pH sensor based on indium-gallium-zinc-oxide electrolyte-gated thin-film transistors (IGZO EGTFTs). (A) Photograph image of IGZO EGTFTs on a 6-inch Si/SiO2 (300 nm) wafer substrate (in total, 60 cells were fabricated). (B) Schematic illustration of a single chip (1.5 × 1.5 cm2) consisting of 20 EGTFTs and respective interconnected pads. (C) Microscope image of individual IGZO EGTFTs with source/drain (S/D) Au electrodes (yellow character), SU-8 passivation (white character), and IGZO sensing layer (green character and dot). (D) Transfer and (E) output characteristics (VTG = 0.5 V) by leveraged pH levels from 4 to 8. (F) The plots of threshold voltage (VTH) of IGZO EGTFT (VD = 0.5 V) against pH levels. The dashed red line indicates a linear fitting from the experimental data. The error bars were calculated from three parallel experiments. (G) Dynamics of drain current (ID) under different pH with the time intervals of 1 s, where the VG and VD were fixed at 0.5 V.
