The Study Of Photo-Modulated Thin Film Transistor Based On Quantum Dots And Low Dimension Carbon Material

Photodetectors have broad applications at remote sensing,navigation,spectrum measurements,Infrared?IR?imaging,industrial control,which have significant meanings for economy development and national security.Recently,the commercial photodetectors depended on molecular beam epitaxy,MBE and Metal organic chemical vapor deposition,MOCVD)and many nano-fabrication processes to form the low-dimensional semiconductor structure and photoelectric signal's read-out circuit.Thus,with the development of informatics technology,it is essential to promote it into future large-area detecting arrays and flexible substrate for meeting the pratical need.The conventional photodetector's high fabrication temperature and expensive processes constrained the photodetectors' application in these areas.Due to high photo-electric efficiency,quick response time of nano photonic materials,the photodetectors with new nanomateirlas and nanostructures attracted many attentions in the scientific field.Meanwhile,compared with traditional photodiodes,tripolar photo-modulated TFT has current self-amplification ability to achieve better photo-electric properties.To avoid the high temperature fabrication processes and complex micro-nano semiconductor processes,this thesis fully used the chemical synthesis for QDs and low-dimensional carbon materials and for fabricating the novel photodetectors uinte with room temperature spin-coating or printing process.In addition,it combined the photodetectors with the high-performance thin film transistor?TFT?to realize the TFT structure phototransistors.This research works broaden a new road for the large-area flexible photodetectors.The research works and achievements are as follows:1.Firstly,CdSe QDs were applicated in conventional Indium Gadium Znic Oxide?IGZO?TFT directly to promote photo-electric conversion and verify the possibility to form the photo-modulated TFT with QDs.The research results demonstrated that:compared with the traditional IGZO TFT within short Ultraviolet?UV?wavelengths,the phototransistor can broaden at least 1 time and amplify responsivity 1000 times at weak incident power?450nm,40 ?W/cm²?.This research results also reveal that due to the low carrier injection rate from QDs to channel,the device also shows low mobility and slow detecting speed disadvantages.This achievement wass published on Applied Physics Letters,104?11?,p.113501,2014.2.Employ high mobility low-dimensional carbon materials to overcome the drawbacks like slow detecting rate during the utilization of QDs.To overcome previous drawbacks,the low-dimensional carbon materials with high electric mobility are taken into consideration to fabricate the photodetector.It can be explored to combine these two components,which can promote device mobility and enhance the photoelectric conversion rate.Through experiments,?1?The photo-generated carrier inside QDs can be transferred to graphene.The schottoky photodiode can obtain a quick photocurrent response benefiting from the high mobility.?2?Graphene with high transpancy?98%?will constrained the decline of the incident light to guarantee an efficient absorption.?3?.The room temperature spin-coatin and radio-freqeucy sputtering were used to deposit QDs,RGO and single-layer graphene for the flexible schttoky photodiode.This achievement was published on ACS applied material interface,7?4?,p.2452-58,2015.3.Given that fabricating the appreprate circuit unite for photo-sensing QDs component,the high performance Graphene nanomesh?GNM?TFT was designed and fabricated.The low-dimensional materials transistor with excellent electric performances and gate-modulated transistor is the key signal read-out circuit component of photo-modulated TFT.But graphene with zero-bandgap energy level cannot close reverse current,and possesses low on/off ratio.GNM use quantum confinement of the nanostructure to open bandgap effectivly.The GNM TFT increases on/off ratio at 30 to grantee the high mobility(400 cm²V^-1S^-1)and lower down the reverse current at 100 nA.This GNM TFT has ability to compose phototransistor.4.Surface modification processes were used to build the charge transfer channel between QDs and GNM which is the foundation of the QDs/GNM photo-modulated TFT.Based on above research results,the carreier transfer efficiency and rate are the vital factors for the photo-electric conversion,detecting speed and other performances of photo-modulated TFT.Therefore,this thesis formed the charge transfer mode between QDs and GNM,where the carrier's transport mechanism was researched.Finally,the charge transfer channel between these two components was built to promote the performances effectively.This experimental results demonstrate that the charge inside QDs can tunnel into GNM under built-in field by gate's field effect.QDs/GNM photo-modulated TFT's on/off ration can reach up to 9.1 which increases on/off ratio 10 times compared with conventional graphene-based phototransistor.Besides,this device's responsivity can reach 2000A/W with quick response time,which is apply to be utilized in the high-performance photo-detecting device.This achievement was published on Nanoscale,7?9?,p.4242-49,2015.