Investigation On Ferroelectric Field Effect Based On In_2-xCr_xO₃ Thin Film/PMN-PT Single Crystal Heterostructure

Field effect transistors?FETs?have multiple advantages of low power consumption,strong radiation resistance,good thermal stability,etc.They are not only widely used in ferroelectric memory,capacitor devices and other microelectronic devices,but also important devices to study the physical effects such as interface charge effect,magnetoelectric coupling effect and quantum Hall effect.However,due to the limitation of the traditional gate,the FETs cannot meet the requirements of large-scale,non-volatile control.Therefore,researchers attempted to replace the traditional insulating gate materials with high performance ferroelectric materials,and constructed a novel type of FETs——ferroelectric field effect transistors?FeFETs?.FeFETs are mainly composed of ferroelectric gate materials and multifunctional films.Because of the residual polarization of the ferroelectric materials,the reversible and non-volatile control of the carrier concentration and its related properties could be realized by the ferroelectric field effect.Moreover,the In₂O₃-based semiconductors have advantages of large direct band gap,high carrier mobility and high visible light transmittance.Moreover,the carrier concentration of the In₂O₃-based semiconductors is relatively low,which makes it possible for us to design In₂O₃-based Fe FETs with the large-scale and non-volatile regulation performance.To sum up,we fabricated the In_2-xCr_xO₃ thin films on the?1-x?Pb Mg_1/3Nb_2/3O₃-x Pb Ti O₃?PMN-PT?ferroelectric single crystals in the form of Fe FETs and focused the research work on the following aspects:?1?In_2-xCr_xO₃films were grown on?001?-oriented and?111?-oriented PMN-PT ferroelectric single crystal substrates by pulsed laser deposition in the form of Fe FETs.The effects of deposition temperature,deposition pressure,substrate orientation and film thickness on the structure,morphology,electrical properties and ferroelectric field effect of the films were systematically studied.The results show that the optimum preparation conditions are T=600?,P=25 Pa and PMN-PT?111?substrate.Moreover,because the ferroelectric field effect is an interface effect,the thin film with small thickness?d=25 nm?can be greatly regulated.?2?Different Cr-doped In_2-xCr_xO₃?0?x?0.11?films were grown on?111?-oriented PMN-PT substrates.The effects of substrate polarization reversal on the carrier concentration,Fermi level,resistance and magnetoresistance were studied by applying an electric field along the thickness direction to PMN-PT.The results show that the polarization charge induced by the electric field can regulate the electron-electron interaction,weak localization and various electron scattering effects in the film,and finally affect the electric transport properties.In addition,the two-band model and the Khosla-Fischer model are used to fit the low-temperature magnetoresistance data of the films.It can be found that the positive magnetoresistance of the In_2-xCr_xO₃ film is mainly due to the energy level splitting caused by the s-d exchange,while the negative magnetoresistance is related to the suppression of spin scattering by the magnetic field.We find that the positive magnetoresistance component MR?+?caused by energy level splitting is more sensitive to the carrier concentration than the negative magnetoresistance component MR?-?,so the change of carrier concentration caused by temperature and ferroelectric field effect mainly depends on the change of MR?+?.?3?Based on In_2-xCr_xO₃/PMN-PT Fe FETs,we analyzed the reliability and stability of the devices from the perspective of application,and combined with new regulatory means such as ionic liquid and light illumination to realize multi-state storage.With the application of positive and negative electric field pulses to the In_1.89Cr_0.11O₃/PMN-PT heterostructure,the resistance variation of In_1.89Cr_0.11O₃ film reaches 52277%,and it can be switched back and forth between stable low resistance state?“ON”?and high resistance state?“OFF”?.The“ON”and“OFF”states are stable after more than 200pulse cycles or removing the electric field for more than 12 hours.In addition,by combining the ionic liquid DEME-TFSI or light illumination with PMN-PT ferroelectric gate,the storage density of the In_2-xCr_xO₃/PMN-PT Fe FET was increased,and the regulation mechanism of various regulation means was also discussed.