Preparation And Research Of Organic Thin Film Transistor Based On The HfO_x Dielectric Layer

Organic thin film transistors(organic thin film transistors,OTFTs)have many advantages such as lightweight,bendable and have affluent crafts selection,which draws a mounting number of attention and makes OTFTs developed rapidly in the past ten years.As a popular direction in the scopes of thin film transistor,OTFTs are widely used in microelectronics and semiconductor industry.Nevertheless,there are still many obstacles in the successful commercialization of OTFTs,such as high driving voltage,low mobility and low stability,especially the large energy consumption dilemma of OTFTs working under high voltage limits the application.While OTFTs used inorganic metal oxide with high dielectric constant as the gate dielectric layer can work under a low driving voltage,thereby effectively reducing energy consumption.In this paper,the performance of OTFT devices with HfO_x as the dielectric layer is studied,and on the basis,we studied the corresponding improvement of the device.This paper is mainly about these works: 1?we studied the device with pure metal oxide HfO_x inorganic material as a dielectric layer,pentacene material as the active layer,the Au metal as the source drain electrode.By analyzing the electrical parameters of the device,we found that using inorganic metal oxides HfO_x materials as a dielectric layer can significantly reduce the threshold voltage of the device.However,other performance of the device still needs to be improved.The on/off ratio is 182,the carrier mobility is only 0.002 cm2/Vs,and the device has obviously hysteresis.2?for further optimizing device,this paper studied the effect on the performance of the device when used different organic polymer materials as a interface modification of dielectric layer and the active layer,including polystyrene(PS),polyvinyl alcohol(PVA)and polymethyl methacrylate(PMMA).Experimental results reveal that when using different organic materials as modified layer,the correlation property of OTFT also has a big difference.The effect of PVA is the worst among them,while the PMMA performs best and it makes the mobility improved to 0.054 cm2/Vs,and the on/off ratio has an order of magnitude improvement reaching 3.31?103.The OTFT with PS performs medium,but it has no delaying.3?in the end,the thickness of HfO_x dielectric layer is optimized by controlling the different concentrations of precursor solution after selecting the proper organic polymer material PS as modification.We manufactured the OTFT devices with different thickness of the dielectric layer to studied their performances.Results show that as the thickness of the dielectric layer increases,the roughness and the threshold voltage of the device increase correspondingly.Among these devices,the OTFT with dielectric of 96 nm shows a good overall performance.Its carrier mobility is 0.041 cm2/Vs,the threshold voltages is as low as-0.56 V and the subthreshold slope is 0.51 V/dec.