The Study On Interface Modification Of Thin-film Transistors And Related Devices

Thin-film transistor(TFT)is a kind of field-effect device that composed of deposited semiconductor,metal and insulator.Recently,TFT has been attracting great attention due to the application in new electrical devices,especially for OTFT and MO-TFT.OTFT' advantages in their great flexibility,solution-processable,low preparation temperature and scalability to large areas have attracted tremendous attention.While the MO-TFT would be widely applied because of the development in solution processing and its advantages in mobility and stability.However,as most OTFT materials are p type and most MOTFT materials are n type,the difficulty in realizing ambipolar conduction restricts their applications.In order to solve this problem,this research combines OTFT and MOTFT to expand the application of TFT in the inverter and the light-emiting transistor.This thesis conducts researches on OTFT performance.Concerning the influence of insulator on OTFT performance,we improve the performance through modifying the surface of insulator.One method for modification is to apply cytop which is highly hydrophobic and low dielectric constant to cover-OH of insulator,and then formulates a semiconductor-insulator interface that shows characteristics of smoother,lower surface energy,lower polar,lower density of states,which is better for the growth of pentacene on the surface.In this circumstance the pentacene grains get larger and the performance of mobility and stability gets improved.Another method for modification is to construct a ODPA SAM to improve the performance on the insulator interface as well as the preparation of solution-processed organic semiconductor.The construction of SAM contributes to the disappearance of-OH on the insulator surface by reaction and formulates a neatly arranged interface that forms a smooth and low-energy surface for the solution-processed organic semiconductor on the top as well as maintain the high dielectric constant of inorganic insulator,so as to realize the preparation of OTFT with high mobility in low voltage.Hence,both methods require low temperature and based on this the authors construct flexible OTFT devices on flexible substrate.This research prepares the OTFT memory with nanoparticle floating gate,with gold nanoparticle as floating gate,PMMA as tunneling insulator and bipolar organic semiconductor PDPP-V as active semiconductor.As bipolar materials equip with both hole and electron carriers,we produce an organic storage on which programming and erasing can be done only through the changing of gate voltage.Bipolar TFT have an advantage in logic circuit over single polar TFT.Combining the advantages of both n-type metal oxide semiconductors and p-type organic semiconductors,this research applies InOx with low temperature solution-processed patterning process the n-type semiconductor and pentacene as p-type semiconductor to prepare bipolar TFT with high stability on the cytop-modified organic-inorganic interface.In addition,this research applies InOx as the n-type semiconductor and solution-processed organic semiconductor FBT-Th4(1,4)as p-type semiconductor and successfully prepare bipolar TFT devices with both electron mobility and hole mobility over 1 cm2 V-1 s-1 by optimizing the interface with ODPA.Based on the bipolar TFT with a heterojunction structure of pentacene/InOx,this research prepares bipolar inverters with the highest gain reaching 160.In order to regulate the overall performance of inverter,this research applies In Ox doping with Sc as the n-type semiconductor to fabricate bipolar inverter with good performance through regulating the concentration of Sc.The inverter can work in first and third quadrants.The switch voltage reaches 97% of the ideal value when VDD is at-30 V.The noise margin reaches 53% of theoretical value(industrial applications require more than 10%).Voltage transition width is only 1.8 V.The inverter can make good response to the square wave signal at100 Hz.This research fabricates the LET through inserting luminescent layer in the bipolar TFT based on pentacene/InOx heterojunction.Then through inserting the PVK layer to modify the injection of hole carrier,we have successfully created LET with both functions of luminescence and switch.This experiment first fabricates the LET using the n-type metal-oxide semiconductor as the electron transport layer,the quantum dot as the luminescent layer and the organic semiconductor as the holetransport layer.This project makes full use of the advantages of the materials,and provide a novel dimension for the choice of LET materials.