Room temperature ZnO nanorods based TFT ammonia sensor: an experimental and simulation study

This study presents a method for growing and characterizing isolated and coalesced ZnO nanorods on a SiO₂/p-Si substrate using the chemical bath deposition (CBD) technique. Characterizations of the nanorods were investigated using an X-ray diffractometer (XRD), atomic force microscopy (AFM), photoluminescence spectrofluorometer, and I–V parameter analyzer. The growth of ZnO nanorods significantly impacts the coalesced surface morphology and quantitative structural parameters. Potentiality of the ZnO nanorods based thin film transistor (TFT) as NH₃ gas sensor has been explored. Experimental findings of the fabricated device structure were found to be well in agreement with the similar prototype structure simulated in TCAD environment. Maximum drain currents deviation between simulation and experimental study were found to be negligibly ± 0.2%. The ZnO nanorods-based TFT exhibits excellent room temperature sensitivity of ~ 226% at 50 ppm NH₃ with threshold voltage shift towards lower V_GS (from 9 V in air to 6 V in 50 ppm NH₃). The fast response (14 s) and recovery (4 s) characteristics of the TFT sensor proved to be potentiality towards ammonia leakage detection and making it highly useful for industrial safety applications. The room temperature nanorods ammonia sensing mechanism were correlated through band bending at the grain boundaries interfaces following neck-controlled depletion model.