An Analytical Model for Dual Gate Piezoelectrically Sensitive ZnO Thin Film Transistors

Abstract

Highly sensitive force sensors of piezoelectric zinc oxide (ZnO) dual‐gate thin film transistors (TFTs) are reported together with an analytical model that elucidates the physical origins of their response. The dual‐gate TFTs are fabricated on a polyimide substrate and exhibited a field effect mobility of ≈5 cm2 V−1 s−1, Imax/Imin ratio of 107, and a subthreshold slope of 700 mV dec−1, and demonstrated static and transient current changes under external forces with varying amplitude and polarity in different gate bias regimes. To understand the current modulation of the dual‐gate TFT with independently biased top and bottom gates, an analytical model is developed. The model includes accumulation channels at both surfaces and a bulk channel within the film and accounts for the force‐induced piezoelectric charge density. The microscopic piezoelectric response that modulates the energy‐band edges and correspondent current–voltage characteristics are accurately portrayed by this model. Finally, the field‐tunable force response in single TFT is demonstrated as a function of independent bias for the top and bottom gates with a force response range from −0.29 to 22.7 nA mN−1. This work utilizes intuitive analytical models to shed light on the correlation between the material properties with the force response in piezoelectric TFTs.

Fundamentals and Applications of ZnO-Nanowire-Based Piezotronics and Piezo-Phototronics

“…The piezoelectric potential generated when ZnO NWs are bent can act as a stress switch. This kind of device driven by mechanical deformation action is called a piezotronics device, which can be used to regulate the performance of sensors [ 34 , 35 , 36 ] and prepare piezoelectric diodes and piezoelectric field effect transistors [ 6 , 37 , 38 , 39 ].…”

“…Schottky barrier modulation at the interface of the two transistors exhibited asymmetric behavior due to the piezoelectric effect, which was consistent with previous experimental results. Wu et al studied the current modulation and piezoelectric response of the dual-gate ZnO thin-film transistor (TFT) through experiments and analysis [ 38 ]. The analytical model reproduced the experimental piezoelectric response of the two-gate TFT well.…”