Combined effects of NH₃ and NF₃ post plasma treatment on the performance of spray coated ZnO thin film transistors

We investigate the effects of NH₃ and NF₃ post plasma-treatment on the performance of spray-coated ZnO thin film transistors (TFTs). Both NH₃ and NF₃ plasma treatment are varied from 10 to 40 s. The properties of plasma treated ZnO were studied by Hall Effect measurements, UV–visible spectroscopy, photoluminescence, atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. NF₃ plasma treatment causes n-type doping and generates carriers by F incorporation. While, NH₃ plasma can cause not only n-type doping by Hydrogen incorporation but also creates acceptor-like states by the formation of V_o–H complex and inducing Nitrogen in ZnO. Owing to the N incorporation, the threshold voltage can be controlled by NH₃ plasma treatment. The appropriate NH₃ and NF₃ plasma treatments for 10 s each greatly enhance the performance of ZnO TFTs, exhibiting the saturation mobility and subthreshold swing of 20.65 cm² V⁻¹ s⁻¹ and 0.18 V dec^–1, respectively. Therefore, it is concluded that NH₃ and NF₃ plasma-treatment can be a useful technique to enhance the device performance and to improve the stability of solution-processed metal-oxide TFTs.