| At present,there are many research reports on organic thin film transistors prepared by solution method around the world,but there are few studies on the effects of polymer interface modification on the performance of thin film transistors.In order to improve the electrical properties of phthalocyanine thin film transistors,obtain high mobility and low threshold voltage transistor devices,PMMA and PVP were spin-coated on SiO2 insulating layers with n-type heavily doped Si substrates.We studied the performance of nitrogen dioxide gas sensor based on polymer interface modification,and surface morphology,capacitance characteristics of the composite film and the electrical properties of the transfer output of the phthalocyanine thin film transistor device.We first studied the surface morphology and roughness of a single-layer SiO2substrate by atomic force microscopy?AFM?.It was found that the surface roughness of the SiO2 substrate without polymer modification was about 0.88 nm or more,Then,the double insulating layers based on SiO2/PMMA and SiO2/PVP were studied.The results showed that the PMMA solution with chloroform as the solvent reduced the surface roughness of the composite film to 0.45 nm.The surface roughness of the composite film was reduced to 0.22 nm by using PVP solution with absolute ethanol as solvent.The single domain size of p-6P films modified by PMMA and PVP interface reaches 68?m and 4?m,which is more favorable for the growth of organic materials than that of p-6P films grown directly on SiO2?single domain size is 1?m?.The thin films grown on it are smoother,regular and orderly,and have fewer trap defects,which lays a foundation for the preparation of high performance thin film transistors.The capacitance characteristics of SiO2,SiO2/PVP and SiO2/PMMA were investigated.It was found that the capacitance of the single-layer SiO2 insulating layer was very high,reaching 10.1 nF/cm2.The capacitance values of the modified SiO2/PMMA and SiO2/PVP insulation layers decreased to varying degrees,reaching 7.7 nF/cm2 and 7.9 nF/cm2.The PMMA/p-6P/VOPc sensor devices based on PMMA interface modification have improved the current response and recovery at 10,20 and 25 ppm gas concentration,and increased about twice at 10 ppm.Finally,the effect of two polymer interface modification on the electrical properties of phthalocyanine thin film transistors was studied.The VOPc/Rub heterojunction thin film transistor was fabricated,and the SiO2/PMMA transistor device migration was obtained.The rate reached 0.27 cm2/Vs.The mobility of transistor devices based on SiO2/PVP reaches 0.064 cm2/Vs,the overall mobility of heterojunction devices is increased by about ten times,and the saturation current is increased by one order of magnitude.Therefore,the phthalocyanine thin film transistor prepared based on the modification of the polymer interface has a good application prospect in the field of realizing high performance OTFT devices. |
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