Improvement Of Contact In Pentacene Thin-film Transistors And Corresponding CMOS-inverters

Due to their wide sources,low costs,large area processing,good compatibility with flexible substrates,and adjustable photoelectric performance,organic semiconductor materials have certain competitive advantages.The field effect transistors prepared by them also show certain application potential.With the joint efforts of researchers in the field,the mobility of some organic field effect transistors has even exceeded the level of amorphous silicon thin film transistors.As the performance of organic field-effect transistor devices continues to increase,the problem of metal-to-semiconductor interface contact becomes more prominent.The existence of interface contact will result in inaccurate evaluation of device performance,and will also limit the application of organic field effect transistors in actual production.Therefore,it is important to effectively improve the contact between the metal electrode and the active layer interface in the organic field effect transistor device.In this thesis,a representative high mobility organic small molecular material pentacene is selected to study the interface contact problem of high performance thin film transistors prepared by it and improve it.The main body of this thesis is divided into two parts.The first part is devoted to improving the interface contact of the field effect transistor,thereby improving the charge injection efficiency and improving the performance of the field effect transistor.The second part explores the pentacene field effect transistor in the digital Application in circuit CMOS inverters.1.The contact barrier between the metal work function and the semiconductor determines the contact resistance between them.We improve the interface contact by inserting a thin layer of MoO₃ buffer layer at the interface of the pentacene active layer and the gold electrode,and evaluate the device performance using two parameters:reliability factor and effective mobility.When the thickness of the MoO₃ buffer layer is changed,the calculated mobility exhibits a first drop,then remains flat,and finally rises again;while the reliability factor is poor at the beginning,then the reliability factor increases,and then becomes worse again when it is thicker.During the entire thickness variation of MoO₃,the effective mobility of the device is maintained at 0.5±0.1 cm²/Vs,which indicates the effectiveness of this method for device performance evaluation.When the optimum thickness of the metal oxide MoO₃ buffer layer is up to 3 nm,the saturation current is increased to 1.4 times,the effective mobility is increased to 1.5times,and the threshold voltage is decreased compared to the thin film transistor device without the MoO₃ buffer layer.The buffer layer effectively improves the contact of the gold electrode with the pentacene interface.2.Organic field effect transistors can be applied to flexible screens,RF tags,large area sensors,etc.,so we explore the application of pentacene thin film transistors in digital circuit CMOS inverters.Based on the p-channel device and pentacene thin film transistor and n-channel device PTCDI-Ph thin film transistor,a CMOS inverter is constructed,and the static transmission characteristics of the CMOS inverter are studied.The working mechanism of transistors in CMOS inverters.The CMOS inverter exhibits good noise margin and narrow uncertainty region width,indicating the potential application of organic field effect transistors in digital circuits.In summary,based on the high mobility organic small molecule pentacene,we have studied the addition of metal oxide as a buffer layer to the interface between the gold electrode and the pentacene active layer to improve the contact effect in the organic field effect transistor.The addition of the buffer layer has significantly improved the performance of the device.At the same time,we can clearly see the feasibility of reliability factor and effective mobility for device performance evaluation.In addition,we built a CMOS inverter based on a pentacene thin film transistor.The CMOS inverter exhibits better static transmission characteristics,indicating the potential application of organic field effect transistors in digital circuits.