Fabrication And Study Of Functional Electronic Devices Based On Carbon Nanotube Thin-Film Transistors

With the development of basic theory and improvement of fabrication technology,study on carbon nanotube thin film transistor?CNT-TFT?has gradually transited from primary physical property to practical application,which shows broad development and application prospect in various fields.However,there are still some key problems need to be solved on the aspect of performance improvement,such as electrical properties including contact and hysteresis,Complementary Metal-Oxide-Semiconductor?CMOS?integration methods,and study of radiation-hardness devices.Therefore,this paper mainly focuses on functional electronic devices based on CNT-TFTs in various application fields and study intensively on some key points,trying to find research directions and lay foundations for future potential applications.Firstly,influence on electrical properties of transistors caused by contact form of semiconductor channel and metal electrode is studied in this paper.Current directionality is observed in TFTs with asymmetric contact form,which proves the relative position of semiconductor channel and metal electrode can influence electrical properties and contact resistance of transistors.Furthermore,through comparative test,the difference between effective Schottky barriers(?_SB)is proved to be the inherent mechanism caused by different contact forms.The result demonstrates that besides work function of semiconductor and metal,relative contact form can also affect the Schottky barrier between them.Temperature-changing method is used to measure the height of?_SB under different contact forms and the result which?_SBB of metal on semiconductor is smaller has been found.Finally,high-performance asymmetric contact form Schottky diodes based on CNT and MoS₂ are fabricated and successfully used in rectification circuits.Furthermore,to solve the CMOS integration problems on the aspect of fabrication technology and electrical matching of N-type and P-type carbon nanotube thin film transistors,a three-dimensional structure integration method is designed in this paper.By stacking P-type CNT-TFTs on top of the N-type ones,high-performance and high integration level CMOS logic devices are achieved including logic gates and ring oscillators.The basic inverter units of this work show great electrical properties such as high inverter gain near 40,large noise margin over 92%,and stable transfer threshold and high/low electrical levels.Using Polyimide?PI?as substrates can fabricate flexible three dimensional CMOS logic devices.Flexible and fatigue tests show that the flexible logic devices can work normally under bending radius as small as 3.16 mm or after over 1000times bend,which demonstrate a stable application of medium-scale flexible logic circuit.Finally,a systematic experiment is designed to compare electrical performance change after gamma-ray radiation on carbon nanotube thin film transistors with various channel materials and polarities.Statistics of key electrical parameters are extracted and compared to find out different mechanisms of different kinds of CNT-TFTs caused by radiation.Thus,specific targeted solutions can be provided for different kinds of CNT-TFTs to improve radiation-hardness ability respectively.Additionally,radiation-stable ambipolar CNT-TFTs and CMOS-like logic inverters consist by them are designed and fabricated,which show high radiation hardness performance.