Preparation And Application Of Low-voltage Flexible Printed Carbon Nanotube Thin Film Transistors

Semiconducting single-walled carbon nanotubes(sc-SWCNTs)have stable physical and chemical properties,good mechanical flexibility,and short channel immunity,which are considered to be one of the most promising semiconductor materials in the post-Moore era.The research of sc-SWCNTs based thin film transistors(TFTs)have become the focus to promote the development of carbon-based chips.However,due to compatibility limitations of processes and materials,the construction of large-area,low-voltage(<2 V)flexible sc-SWCNTs based TFTs still face challenges.In this thesis,we construct the flexible large-area,low-voltage sc-SWCNTs TFT arrays(19×8)with the ultra-thin AlO_X dielectric layers obtained on the surface of alumina gate electrodes using oxygen plasma oxidation method.We innovatively solved the high leakage current problem from the perspective of electrodes by using ultra-thin AlO_X(?3.6 nm)to directly construct transistors.The enhanced mode sc-SWCNT TFTs is first constructed with low work function aluminum as the gate electrode from the process optimization,which further reducing the power consumption of printed carbon-based electronic circuits.The applications of NO₂ sensors,low power-consumption CMOS inverters and NAND circuit were carried out around low operating voltage and flexible printed carbon nanotube thin film transistors.The core content and conclusions are list as follows:(1)Construction of low-voltage transistors.An ultra-thin(?3.6 nm)AlO_Xdielectric layer is formed on the surface of alumina gate electrode with oxygen plasma technology.A low-cost screen-printing technology is used to construct silver source and drain contact electrodes,afterwards,sc-SWCNT TFTs array is realized on a variety of flexible substrates with low operation voltage.The as-prepared transistor exhibits a low leakage current about?10^-10 A(100 times lower),which solves the problem of high leakage current of transistors when directly using the ultra-thin alumina oxide as dielectric layer by with oxygen technology.In addition,the transistor has high charge carrier mobility(up to 9.9 cm²V^-1s^-1),high on/off ratios(>10⁵),good mechanical flexibility,air stability and bias stability at low operating voltage(?-1.5–0.5 V).(2)Construction of flexible sensors.Considering the harm of NO₂ to the human respiratory tract and the NO₂ sensors prepared are mostly rigid,on the basis of the research of(1),a flexible transistor-type NO₂ sensor was developed.The performance of transistor-type and resistance-type sensors is compared in terms of response time,responsivity and detection limit,which proves the signal amplification effect of transistor-type sensors.The detection limit is as low as 0.069 and the minimum detection concentration is as low as 0.5 ppm.On the basis of this research,it is expected to develop a new multifunctional sensor array and detect different gas signals in real-time monitoring.(3)Construction of low-power consumption circuits.The enhanced mode sc-SWCNT TFTs(0 V on)were successfully obtained by optimizing the screen-printing process,the concentration of sc-SWCNTs ink and printing times.These kinds of sc-SWCNT TFTs were used to build ultra-low power consumption CMOS inverters and NAND circuit on a variety of flexible substrates.For example,paper-based CMOS inverters show excellent properties with the power consumption as low as 63.83 fW/?m,rail-to-rail output characteristics at?V_DD/2,the voltage gain up to 32 when the V_DD is1 V,and the noise tolerance as high as 92%.Furthermore,the constructed NAND circuit can realize the corresponding logic function.Based on this work,it is expected to build a more complex ultra-low power electronic circuit system,which is of great significance to the development of low power consumption carbon-based electronic circuits.