The Effect Of WO₃ Modified Layer On OFET Performance And Electrode Structure Simulation

OFETs has the advantages of flexibility,large area production,simple manufacturing process,etc.,which has attracted the interest of many researchers.With the improving of the mobility,OFETs has been successfully applied to the radio frequency identification(RFID)tag,flexible display,biological sensors and other fields.At present,it may be further extended to THz wave detection field to realize the application of portable THz wave detector with small size and light weight.This paper mainly studies two parts,which are the effect of electrode modification on the electrical properties of OFETs,and the simulation and optimization of the electrode structure to improve the THz absorption performance.First,this article discusses the effect of different electrode materials on the performance of OFETs.Au and Cu electrode OFETs were fabricated respectively using bottom-gate top-contact device structures,low-doping high-resistivity(1-5?·cm)n-type silicon as the gate and substrate,and pentacene as the organic semiconductor material.Next we discussed and analyzed the electrical performance parameters and proposed a scheme to improve the performance of Cu electrode OFETs by electrode modification.Then,the influence of the thickness of WO3 modified layer on the performance of Cu electrode OFETs was studied.We prepared devices with different channel lengths under different modified layer thicknesses,and discussed the relationship between device performance,contact resistance and thickness of the modified layer,determined that when the thickness of WO3 modified layer was 0.5nm,the contact resistance between electrode and organic semiconductor layer is the minimum and the electrical properties of the device has been improved the most.Through the XPS test,it is found that the electric charge transfer from Cu to WO3 modified layer at the contact area to form a high conductivity region.At the same time,the WO3 as barrier layer,can effectively suppress the generation of the interface dipole layer between the Cu electrode and the pentacene layer,thus reducing the carrier injection potential.In the simulation part,the FDTD Solutions software was used to build the model from two aspects:the width and spacing of the electrode.The effect of different structure sizes on the THz absorption at different positions of the pentacene layer are discussed.Simulations show that as the width of the electrode increases or the spacing decreases,the absorption rate of pentacene to THz wave in the OFETs will increase.The main reason is that when THz wave incidents to Cu electrode surface of subwavelength size,surface plasmon resonance is generated,which leads to the enhancement of the local electric field in the pentacene layer,and thus promotes the enhancement of THz wave absorption in the local position of pentacene layer.The electrode size used in the simulation provides a reference for optimizing electrode structure.