Preparation And Electrical Properties Of Two-dimensional ?-In₂Se₃ Ferroelectric Transistor Based On Ion Gate Modulation

Traditional ferroelectric thin films were generally used as gate insulators,and due to the presence of defects,charge trapping and high current leakage often appears.?-In₂Se₃ is a Van der Waals semiconductor with stable ferroelectric property at room temperature.It can be directly used as a channel material in Ferroelectric Semiconductor field-effect transistor(Fe S-FET)which has memory characteristic and high on/off ratios.However,using traditional silicon oxide based gate dielectrics also faces challenges in high working voltage.Experiments have shown that the electrical double layer of the ion gel and ionic liquid can bring powerful field regulation capabilities which can effectively reduce the power consumption and working voltage of the device.In this work,we explore the ferro-electricity and corresponding electrical properties of?-In₂Se₃ by preparing?-In₂Se₃ transistors of different configurations.Then,we prepared an electric double-layer transistor of?-In₂Se₃ by integrating ionic gel/liquid and explored the modulation of ion gate on the channel.The main contents are as follows:(1)Two-dimensional?-In₂Se₃ was obtained by mechanical exfoliation,and the out-of-plane ferroelectric polarization switching characteristics were measured by piezoresponse force microscopy(PFM)method.We observed that the obtained?-In₂Se₃ had a random initial ferroelectric polarization orientation.Afterwards,we prepared the Au/?-In₂Se₃/Gr ferroelectric diode and its rectification direction can be changed,the rectification ratio reached10².We prepared the?-In₂Se₃-based Fe S-FET with different metals contacted(Cr,Au)and observed the counterclockwise and crossed forms of hysteresis loop.In the former case,the conductance of the device is dominated by the contact barrier,while the latter is dominated by the change of the conductivity of materials.(2)?-In₂Se₃ based electric double layer Fe S-FET was prepared by using PEO/LiClO₄ as ion gel.After integration,it is found that the window of the I_d-V_d hysteresis loop is significantly increased.It is observed that the ion gated transfer characteristic curve(I_d-V_sg)has clockwise,counterclockwise and crossed forms.We speculate that the ion migration relaxation in the ion gel causes counterclockwise hysteresis,while the ferroelectric polarization switching brings about clockwise hysteresis,and the regulation of the former is volatile,the latter is non-volatile.(3)Using Raman spectroscopy,it is found that the lattice structure of?-In₂Se₃ is destroyed on high working voltage after integration of ion gel.Using[EMIM-TFSI]ionic liquid instead of PEO/Li⁺also fails to improve this situation.Increasing the thickness of the material helps to improve the stability of the device.But the carrier density of the device is too large to modulate the channel current by the ion gate,limiting the switching ratio is to?2.