Study On Polymer Dielectrics Property And Process In Polymer Transistors

With continuous development of the fundamental understanding of charge-transport in organic field-effect transistors,it is gradually realized that dielectric plays an essential role in improving device performance.There are a large number of dipoles in high-κdielectrics,which influence the density of states and their distributions for the charges transporting along the dielectric/semiconductor interface,resulging in increase of the hopping barrier.By contrast,owing to the lower energetic disorder caused and fewer trap states,low-κdielectric has become most promising candidate for improving the charge transport,but the high operating voltage leads to higher power consumption and thus prevents the portable applications powered by batteries.So,bilayer dielectric is inevitable in this regard.Considering this context,this thesis is performed as follows:First,DPPT-TT OFETs（Organic Field Effect Transistors,OFETs）with a bilayered dielectric of Al₂O₃/PS were fabricated,in which Al₂O₃ fabricated by ALD（Atomic Layer Deposition,ALD）was on top of a spin-coated PS（polystryene）.For comparison,DPPT-TT OFETs with simple dielectric of Al₂O₃ or PS were fabricated too.The thickness of PS was varied by changing its concentration.Then,parameter extraction and analysis were carried out for these devices.Finally,optimum concentration of PS（10-20 mg/ml）was determined by examination of all the devices,and those exhibited both high mobility and low threshold voltage.Second,DPPT-TT OFETs with a bilayered dielectric of Cytop/P（VDF-Tr FE）were fabricated,where P（VDF-Tr FE）was spin-coated on top of a spin-coated Cytop.Similarly,DPPT-TT OFETs with a gate dielectric made of a single-layer Cytop or P（VDF-Tr FE）were fabricated for comparison too.Then,the annealing process of Cytop was optimized and the performance of single-layer dielectric devices with Cytop as gate dielectric was improved.Next,parameter extraction and analysis were carried out for these devices.Finally,experiments were carried out on bilayered devices for different annealing temperature,annealing time and Cytop stock solution.The results showed that abnormal operation of bilayered devices may be attributed to the P（VDF-Tr FE）itself.