Preparation And Photoelectric Detection Performance Of Bismuth Layered Perovskite Ferroelectric Thin Films

Ferroelectric materials are asymmetric materials with switchable polarization.They have shown great potential applications in many fields,such as sensors,memory and so on.In recent years,ferroelectric materials have attracted much attention due to their unique photoelectric properties in photovoltaic and photoelectric detection neighborhoods.The depolarization field in ferroelectric materials can effectively promote the separation of photo generated carriers and improve the photoelectric efficiency in optoelectronic devices.Bismuth layered perovskite ferroelectrics have high spontaneous polarization,good fatigue resistance,environmental protection,and high-temperature stability,making them popular materials for ferroelectric storage and ferroelectric photovoltaic applications.To investigate the properties of bismuth layered perovskite ferroelectric materials as self-powered photodetector and the effect of polarization on the photodetector properties,two kinds of bismuth layered perovskite ferroelectric thin films were prepared,and we have tested its photoelectric detection performance,and deeply studied the mechanism of ferroelectric polarization on the photoelectric performance.The research content and results of this article are as follows:1.We prepared Bi_3.15Nd_0.85Ti₃O₁₂（BNT）thin film on Pt/Ti/Si O₂/Si substrates by sol-gel method,and designed a self-powered ultraviolet photodetector based on this film.It was found that because the depolarization field in BNT ferroelectric thin film can provide a driving force to separate and accelerate photogenerated carriers,so BNT thin film can exhibit excellent photoelectric performance without applying additional voltage.Its responsiveness and detection rate can reach 0.047 m A/W and 1.47×10⁹ Jones,while the response time of BNT film is also short（τ_r=300 ms,τ_d=330 ms）.In addition,the performance of self-powered photodetectors based on BNT can be regulated by controlling the polarization state of ferroelectric thin films.The research in this work show that the BNT device has the best performance after negative polarization,which also can provide a possible method to improve the performance of photodetectors.2.Bi₄La Fe_0.7Co_0.3Ti₃O₁₅（BLFCT）thin films were prepared on NSTO substrate by the pulsed laser deposition technology.And during the preparation we change three process parameters:substrate temperature,oxygen pressure,and laser energy.Subsequently,we characterized the surface morphology and leakage current of BLFCT thin films and then determined the most suitable preparation process for the growth of BLFCT thin films.Finally,we prepared Pt electrodes on the BLFCT film to obtain Pt/BLFCT/NSTO self-powered UV photodetectors.Due to the built-in electric field of the Pt/BLFCT/NSTO heterojunction,which can drive the separation of photogenerated carriers,the device also exhibits excellent photoelectric performance without applying voltage.Under 365 nm illumination of 77.50m W/cm²,the open circuit voltage can reach 0.60 V and the short circuit current density can reach 20.47μA/cm².The response of the device is 1.25 m A/W,and the detection rate is 1.39×10¹⁰ Jones.The BLFCT device also has a short response time（τ_r=179 ms,τ_d=531 ms）.In addition,we found that applying polarized electric fields and magnetic fields also has a certain effect on the photoelectric performance of this device,which also provides a possible way to improve the performance of this type of photodetector and to achieve multifunctional devices.