Preparation Of Cross-Linked High Dielectric Constant Polymer And Its Low-Driving Voltage Thin Film Transistor

Using high dielectric constant materials to prepare thin film transistors can effectively reduce its driving voltage,which is the research focus in the field of high-performance and low-power electronic circuits.However,traditional high dielectric constant materials,such as ceramics and metal oxides,need photolithography and high-temperature processing,which not only increases the cost and reduces the material utilization,but also limits their application in flexible electronic devices in the future.Although some polymer materials have high dielectric constant,the linear molecular structure makes them easy to be destroyed by solvent,which is not conducive to the preparation of multilayer integrated devices.Therefore,it is urgent to design and prepare high dielectric constant polymer materials that can be crosslinked at low temperature,and it is expected to realize the flexibility,low power consumption and printable integration of multilayer electronic circuits.In this paper,polar groups are introduced into the molecular structure to regulate the dielectric constant of polymers,and solvent resistant dielectric films are obtained by low-temperature crosslinking method,so as to realize the low-temperature preparation and low-voltage driving of thin-film transistors.Cross linked poly（2-cyanoethyl acrylate-1,6-hexanediol diacrylate）（C-P（CEA-co-HDDA））was prepared by using-CN containing 2-cyanoethyl acrylate as main monomer（CEA）,1,6-hexanediol diacrylate as spacer（HDDA）and triallyl isocyanurate（TAIC）as cross-linking agent under atmospheric atmosphere and room temperature,its electrical properties were characterized and applied to thin film transistors.The main research work is as followsPreparation of crosslinked high dielectric constant polymer at low temperature.Crosslinked C-P（CEA-co-HDDA）was prepared by optimizing the experimental parameters such as photoinitiation time,water bath heating time and light curing time;Its crystallinity,thermal decomposition and surface morphology were analyzed by XRD,TGA and AFM.The experimental results show that C-P（CEA-co-HDDA）is not only an amorphous polymer;at the same time,it also has a high thermal decomposition temperature.With the different crosslinking degree of the polymer,the initial decomposition temperature is between 238～299℃.The polymer films prepared by solution spin coating method show non porous,dense,uniform and smooth morphology and structure;In addition,patterned polymer films with different resolutions can be formed by selective UV exposure,with a maximum resolution of 2μm.Characterization and mechanism analysis of electrical properties of crosslinked high dielectric constant polymer.Based on metal electrode-polymer-conductive silicon wafer（MIS）capacitor,the electrical properties of C-P（CEA-co-HDDA）with different components were explored.It is found that at 10³ Hz,C-P（CEA-co-HDDA）shows a high dielectric constant of 7.49～9.76,and the dielectric loss tangent is less than 0.06.The high dielectric constant of the polymer not only comes from the-CN group in the system,but also the cross-linking agent TAIC contributes to the dielectric constant at a certain extent.In addition,with the increase of polymer crosslinking degree,the movement of polymer molecular chain is limited,the dependence of dielectric constant on temperature is weakened;at the same time,the hysteresis loops of polymer tends to be more and more linear.Application of crosslinked high dielectric constant polymer in low-driving-voltage thin film transistors.A variety of semiconductor（IGZO,Mo S₂,PDPP2T-TT-OD,C8-BTBT,Ph-BTBT-10）based thin film transistors were prepared with C-P（CEA-co-HDDA）-6-4 as the dielectric layer,and their device performance was analyzed and tested.The results show that the prepared thin-film transistors show good performance and realize low driving voltage（<10 V）,which shows that C-P（CEA-co-HDDA）-6-4can not only realize the low-voltage driving of thin-film transistors,but also have good adaptability to different semiconductors.In addition,the use of various semiconductor processing processes（sputtering,solution spin coating and solution scraping）in the preparation process proves that C-P（CEA-co-HDDA）-6-4 can adapt to complex and diversified device processing processes,which is of great significance for the preparation of large-area electronic devices in the future.In this paper,a series of cross-linked polymer films were prepared efficiently and gently by photoinitiation-water bath heating-UV curing method,and their dielectric properties and applications in thin film transistors were explored.It is found that different dielectric constants can be obtained by adjusting the feed ratio of the polymerization system;the adjustable range of dielectric constant is further increased by changing the type of polymerized monomer.In addition,with the increase of crosslinking degree,the higher the restriction degree of polymer molecular chain,the temperature dependence of dielectric constant decreases,and the hysteresis loop tends to be linear.A variety of semiconductor based thin film transistors constructed with the prepared cross-linked polymer as the dielectric layer show good performance and low driving voltage.This topic provides a new possibility for the large-area and cheap preparation of portable flexible electronic devices in the future.