Fabrication And Performance Investigation Of Flexible Thin-film Transistors With High Dielectric Constant Gate Layer

In recent years,flexible electronics has attracted more and more attention,and has been applied in many fields,such as flexible displays,flexible wearable devices and flexible photosensors.Single-crystalline silicon is considered to be the best semiconductor material in flexible electronics due to its high carrier mobility and being compatible with industrial complementary metal oxide semiconductor(CMOS)process.Flexible thin-film transistors are one of the most essential and fundamental devices in flexible electronics and flexible thin-film transistors with single-crystalline silicon film as active layer and high dielectric constant material as gate dielectric layer are expected to be used in various high performance applications.However,the limitation of them is that most high dielectric constant material with high quality needs to be obtained at high temperature,which is incompatible with flexible substrate.Therefore,it is necessary to find high dielectric constant dielectric material with high quality obtained at room temperature.In this thesis,the traditional CMOS process is combined with the transfer process of single-crystalline silicon film and high performance flexible thin-film transistors based on the high dielectric constant gate dielectric layer were successfully fabricated on a flexible substrate.The high dielectric constant gate dielectric material is selected from double-layer gate dielectric film of ceramic material Nb₂O₃-Bi₂O₃-MgO(BMN)and TiO₂.Both of them can be formed by magnetron sputtering at room temperature and the BMN/TiO₂ gate dielectric film has relatively high dielectric constant,wide band gap and high interface quality with the single-crystalline silicon film.The BMN/TiO₂/Si heterostructure has small leakage current,which proves BMN/TiO₂gate dielectric film is advantageous for realizing high-performance flexible thin-film transistors.The flexible thin-film transistors fabricated have good direct-current characterisctics with a current on/off ratio of over 10⁴,threshold voltage of only?1.2V,subthreshold swing of?0.2 V/dec and have consistent performance with different size.In order to further systematically investigate the effects of gate dielectric material and size on the performance of thin-film transistors,the models of thin-film transistors with different gate dielectric material and size are obtained and their performance was investigated based on software Sentaurus in this thesis.