Fabrication Of Amorphous ZnTiSnO Thin Films And Performances Of TFTs

Amorphous oxide semiconductors (AOSs) have been used as the channel layers of thin-film transistors (TFTs) in the display field due to their special advantages, such as high field-effect mobility, compatibility with flexible substrates and large area deposition. Compared with the industrialized a-InGaZnO TFT, the a-ZnSnO TFT become another hot-spot research issue owing to its indium-free, low-cost and toxic-free characteristics. However, for improving the device performances, it’s necessary to add a fourth element as carrier inhibitors in ZnSnO due to its high density of defects. In addition, AOS TFT can be applied not only in displays but also in sensors such as UV detectors, biosensors and gas sensors, which are another key research area of the AOS TFT technology.In this work, amorphous ZnTiSnO (a-ZTTO) thin films were prepared by a solution combustion method at low temperatures. We studied the influences of Ti doping on film properties through the relevant examinations. The results showed that the morphologies of films changed dramatically with the increment of Ti, from the continuous dense structure to the textured structure interlaced with particles and pits. We also found that the doped Ti could effectively reduce the number of Vo in films to inhibit the carrier concentration.Then a-ZTTO thin films were used as channel layers to prepare TFT devices. We studied the effects of the secondary annealing, channel dimensions and Ti-doping on the electrical performances of devices. The second annealing process could indeed effectively reduce the interfacical defect density in films to improve the electrical performances of devices, while the reducing width-to-length ratio of channels led to the significant degradation of devices performances. The right amount of Ti doping had the ability to improve the electrical performances of TFTs and increase the device stability. When Zn/Ti= 30:1, the a-ZTTO TFT exhibited an optimal performance with Ion/Ioff=3.54×105, μFB=0.77 cm2V-1s-1, Vth= 2.14 V, SS= 1.13 V/decade.In addition, the responsitivity and recovery features of a-ZnSnO TFT were analyzed under the illumination of 365 nm UV. The gate voltage could effectively control the sensitivity and speed of recovery for UV irradiation in the devices. The sensitivity of TFT devices was up to 105 with VGS=-10 V. A theoretical model was proposed to explain the phenomenon, providing a fundamental knowledgement for the TFT devices in the UV detection technology.