Preparation Of Nickelate Films And Their Application In Ferroelectric Memristors

With the increase of Moore's Law becoming slower,as long as facing the chip process limit in the near future,there is urgent demand for new type of materials and architecture which can be applied in next generation memories and computing.Memristors have attained extensive attention for their non-volatile storage,high On-Off ratio,and simple structure.The materials of critical structure of them,dielectric layer,have been widely researched.There are usually top electrodes and bottom electrodes made from oxide films in many memristors.However,the general concern of these films is the match of lattice with dielectric layer and their conductivity.There are few works focus on the materials of electrodes.In this work,pulsed laser deposition(PLD)was used to grow Nd Ni O₃(NNO)and Sm Ni O₃(SNO)films.The growing condition and crystallinity of them was explored.Their conductivity and microstructures were tested too.Research is there that both SNO and NNO has apparent metal-insulator transition.It was found that the temperature of metal-insulator transition of NNO is low,the crystallinity of SNO films prepared by target with exceeding Ni over stoichiometry is relatively poor,and SNO films prepared by stoichiometric target have appropriate properties to be utilized as bottom electrode.Ba Ti O₃(BTO)film was then deposited on SNO to constitute heterostructure.Abnormal coexistence of two types of resistive switching was demonstrated in this device,and the mechanisms beneath the three different resistive states were discussed.At last,this device successfully realized the function of synapses in brain of bio-inspired computing.This dissertation is divided into six chapters:In chapter one,the background of researches and recent progress was introduced.First the theories and concepts of Perovskite structure,the electronic properties and metal-to-insulator transition were introduced.Then the properties of rare-earth nickelates were presented.At last,the recent progress of researches on NNO and SNO,which were discussed in this work,was introduced.In chapter two,the theories and methods of characterization as well as the instruments used in this work were mentioned.The contents from chapter three to chapter five are the experimental results and discussion of this dissertation.In chapter three,the growth condition and the relationship between resistivity and temperature of NNO films was discussed.In chapter four,the growth condition of SNO films was studied,and microstructure characterization of them was performed.Then comparation of SNO films made by different targets was presented.In chapter five,BTO/SNO heterostructure was prepared to form memristor,and abnormal resistive switching was discovered in this memristor.At last this memristor was applied in the realization of the function of synapses in bio-inspired computing.The sixth chapter is the summary and prospect of this dissertation.In this chapter,the results and conclusion of this research was summarized.Then prospect of future work was presented.