Fabrication Of Doped SnO₂ Memristor And Its Characteristics Research

With the development of storage technology,creating a new kind of high-performance storage for replacement,has became a research orientation of modern science.It should not only has the high density integration of dynamic memory,but also can be non-volatile as FLASH,and should be compatible with the mainstream production technology at the same time.Many kinds of memristors has emerged in the past few years,such as resistance random access memory,magnetic random access memory,phase random access memory,ferroelectric random access memory and so on.Memristor has been paid great attentions since it was proposed because of its small size,high density,low power consumption and potential applications in many fields.Against this background,doped SnO₂ memristors have been fabricated through Sol-Gel method in the paper,and Al is used for the top dot-electrodes through vacuum evaporation method.Many characteristics were tested on Mn-doped SnO2,Cu-doped SnO2 and Co-doped SnO2.Here are the main content:（1）the precursor sol was prepared by using SnCl₄·5H₂O,C₂H₅OH,etc.And the elements were doped into the precursor sol by mixing MnCl₂·4H₂O,CuCl₂·2H₂O,CoCl₂·6H₂O respectively.The sol was deposited on the FTO glass by the spin and sintering method.The uniform,neat films can be fabricated after annealing under the temperature of400oC and Al is used for the top dot-electrodes through vacuum evaporation method.Then the 3-layers memristors were made.（2）SEM,AFM,XRD were adopted to chatacterize the doped memristors.The thickness in each spin and sintering method remain stationary,and there is little difference between Mn and Cu element doped SnO2 memristor.Co-doped SnO2 memristor shows the thinnest films in spin and sintering method.The films after annealing is dense,and Co doping formed the highest degree of flatness compared with Mn and Cu doped memristors.The introduction of the dopant elements did not change the original grain structure of SnO2,and the doping elements have no effect on the crystalline structure of the film.Each kind of doping elements show positive effect on the grain size of the film,but had some inhibitory effect on crystallinity.These 3 kinds of elements shows little difference to the structure of grain.（3）I-V tests were performed on the memristors of Al/SnO2:Mn/FTO,Al/SnO2:Cu/FTO,Al/SnO2:Co/FTO structures,respectively.The results are as follows:Set and Reset voltage increases with the thickness increase,the resistive switching ratio also increases with the thickness,and Set voltage and Reset voltage are offset because of the repeated test.Both the Set and Reset voltages of Mn doping memristors are larger than Cu doping.Co-doped memristive switching ratio is minimal,and shows asymmetric resistive switching,which is due to Co doping leads to non-uniform carrier of the film.Different doping makes properties change,such as resistive switching ratio,which may be related to the mismatch of lattice after doping.It also can be found that a thickness threshold exists in the memristor.When the thickness is too thick,the movement of the carrier is affected,making the switch resistance becomes smaller.Mn doping memristors'thickness threshold is less than Cu doping,it can be speculated that Cu doping is more conducive to the formation and movement of carriers.The paper also analyzes the carrier transfer mechanism of the Mn-doped memristor and the Cu-doped memristor.The transport mechanism of the Mn-doped memristor is proved to meet the space charge limited conduction model,while Cu-doped memristors meet the Schottky barrier model.