Synthesis,Film Growth And ?-? Hysteresis Characteristics Study Of Iron Phthalocyanine

The molecular structure of phthalocyanine is highly symmetrical,with physical and chemical stability,and unique photoelectric properties.And the thin film easily adsorbs oxygen.Under the action of an external electric field,ionized oxygen vacancies gradually form a conductive path,showing unique hysteresis characteristics.It is expected to be used as memristors.In this paper,we tested the hysteresis behavior of iron phthalocyanine(FePc)thin film electronic devices and explore the possibility of application in memristors.It is well known that the crystallographic quality of the crystal plays a crucial role in the performance of the devices.This thesis designed and discussed three aspects:raw material synthesis,film growth conditions and device structure.(1)The FePc was successfully synthesized by introducing iron powder,introducing 1,8-diazabicyclo[5.4.0]undecy 1-7-ene,and changing the ratio and concentration of raw materials.The prepared samples were characterized by single crystal X-ray diffractometer,Fourier infrared spectrometer,Ultraviolet visible absorption spectrophotometer,and Field emission scanning electron microscope.The phase,molecular structure and microscopic morphology of the sample were analyzed.Through comparison and analysis of the three groups of samples,we found a green synthesis method of fabricating FePc with high-purity,high-yield and crystallinity.It is only necessary to mix FeCl2·4H2O with 1,2-dimethylbenzene in a ratio of 1:8(2 mmol:16 mmol).Then used ethanol as solvent,and heat them at 190? for 8 hours at constant temperature with solvothermal synthesis.Ethanol and deionized water was repeatedly filtered to obtain FePc.(2)The prepared FePc sample was vapor-deposited into film by organic evaporation,and the sublimation temperature of the FePc was measured by film thickness meter.Sublimation temperature is 380?.The film thickness was measured by a step meter to determine the growth temperature of the FePc film:400?,growth time was 2 h.It was found that the morphology of the FePc film grown at room temperature was spherical,and it became a long strip after heating by in-situ heating experiments.The phase transition of the FePc film did not occur after in-situ heating and annealing,and the UV absorption peak of the in-situ heating sample did not shift.(3)Fabricating six device structures by magnetron sputtering sputtering of metal electrodes:Al/FePc/Al,Co/FePc/Co,Al/FePc/Co,Co/FePc/Al,ITO/FePc/Co and ITO/FePc/Al.The cyclic I-V curve of above six structures were tested and their hysteresis behaviors were analyzed.It was found that the cyclic I-V curve of the Al/FePc/Al,devices was very similar to the hysteresis loop of the ferroelectric memory.The device metal electrode and the internal ionized oxygen vacancies were more involved in hysteresis behavior relative to the contribution of the central metal atom(iron)in the phthalocyanine.Besides,the hysteresis behavior of the device was affected by the applied voltage.When the voltage was less than 10 V,the device's hysteresis loop was similar to the ferroelectric memory;when the voltage was greater than 10 V,the cyclic I-V curve of the device lost symmetry and hysteresis behavior only occurred in the positive voltage range.The cyclic I-V curve of the Co/FePc/Co device exhibited an"8" shape.When a voltage of 50 V was applied,the I-V curve in the first quadrant exhibits a high and low resistance state.Al/FePc/Co and Co/FePc/Al devices had the same hysteresis behaviors of Al/FePc/Al,Co/FePc/Co devices,indicating that the electrodes affect the hysteresis behavior of the devices.(4)ITO/FePc/Co device exhibited resistance change behavior when the test voltage is 5 V,but the cycle curve is unstable.It is indicated that FePc can be used as an intermediate layer of the memristor.ITO/FePc/Al device exhibited memristive behavior,and the shape of the cyclic I-V curve conformed to the characteristics of the complementary resistive switching.The set and reset of the device can be realized under the same polarity,which was a unipolar type.The cause of the hysteresis of the device was caused by the internal ionization oxygen vacancy migration,and accompanied by the redox process of the Al electrode,which belonged to the valence state change memristor.