Research On Memristor Based On Barium Ferrite And Its Application In True Random Number Generator

With the advent of the post-Moore era,the traditional Von Neumann computer architecture is facing a serious memory wall problem,seriously affect the computing speed,which restricts the development of artificial intelligence and big data applications.One of the technologies that promises to break the Von Neumann bottleneck is computing in memory（CIM）.Memristor,as the fourth basic electronic component that really appeared in 2008,has been widely studied in non-volatile storage and brain-inspired computing,and for in-memory computing.At the same time,due to its unique properties,memristors also have excellent application prospects in other fields.At present,the material system of memristors is still expanding,more and more materials exhibit memristive behaviors,but their working mechanisms are different,so their electrical characteristics and application scenarios are also different.Selecting suitable materials to prepare high-performance memristors and applying them in corresponding scenarios is an important research direction.In recent years,memristors based on ferroelectric properties have been widely studied due to their stable resistance state,excellent endurance,fast read and write speed,and high integration.Multiferroic materials with both ferroelectricity and ferromagnetism have attracted great attention because of their additional potential for application in electromagnetic coupling scenarios.As a magnetic material,barium ferrite(BaFe₁₂O₁₉)has long been widely used in the fields of magnetic recording and microwave absorption,but it has also been proved to have ferroelectricity and belongs to multiferroic materials.However,there are few studies on the ferroelectricity of barium ferrite.The research on the resistive switching characteristics is almost blank.In addition,barium ferrite also has the advantages of low cost,good chemical stability,corrosion resistance,and its growth process is compatible with the complementary metal oxide semiconductor（CMOS）process.Therefore,it is of great significance to fabricate memristors based on barium ferrite,study their ferroelectric and resistive properties and explore their applications in integrated circuits.Based on this goal,this study introduced barium ferrite material into memristor for the first time and initially explored its application in circuits.The completed work is as follows:First of all,the barium ferrite material was fully investigated and its growth process was determined.Then,barium ferrite film and Cu/BaFe₁₂O₁₉/Pt structure memristor were prepared on silicon wafer by physical vapor deposition process and the preparation process was introduced in detail.In addition,the detailed physical characterization analysis of barium ferrite thin films from the aspects of morphology,elemental composition,magnetism,ferroelectricity,etc,which showed its good process compatibility and confirmed the existence of multiferroicity in barium ferrite materials.Secondly,a variety of electrical characteristics were tested and analyzed for the prepared Cu/BaFe₁₂O₁₉/Pt structure memristor,including current-voltage characteristics,multiple current compliances characteristics,retention,and cycle endurance.The results show that the memristor with Cu/BaFe₁₂O₁₉/Pt structure can obtain different resistance states under different current compliances.The corresponding resistance states show relatively stable retention and cycle endurance,demonstrating its application potential in multi-bits storage and computing.In addition,the migration energy barriers of copper ions and oxygen ions in barium ferrite films were obtained by first-principles calculations based on functional theory.Combined with Schottky emission model fitting,the resistance switching mechanism of Cu/BaFe₁₂O₁₉/Pt structure memristors is considered to be the result of the joint action of ferroelectric polarization reversal and carrier migration.Finally,based on the unique electrical characteristics of Cu/BaFe₁₂O₁₉/Pt structure memristors,a method for constructing a true random number generator using the non-ideal characteristics of memristors as a random source is proposed,which provides a new idea for the application of memristors.Because the memristor is compatible with the traditional CMOS process,it can greatly reduce the circuit complexity compared with other true random number generation methods and has application prospects in the fields of hardware security and encryption.Therefore,based on the 180nm CMOS process,the relevant peripheral circuits are designed on the Cadence software,including the setting module and the detection module and their functions are verified by simulation.