Study On Performance And Mechanism Of Resistive Switching In Nb: ArTiO₃Single Crystalline Schottky Junctions

The rapid development of the information technology in the present world depends on the continuousimprovement of the performances of the nonvolatile memory. A large number of researchers are looking forsubstitutes of Flash memory in order to obtain the novel memory having more excellent performances. Theresistance switching phenomenon of a lot of oxide materials have been widely concerned because of theapplication in the resistive random access memory （ReRAM）. The unclear resistive switching （RS）mechanism in the oxide materials is the greatest obstacle for further development and the practicalapplication of the ReRAM. The RS effects mainly come from electrons or ions. Compared with that comesfrom ions, the RS effect based on the electron mechanism has advantages of complete elimination of thepotential in the electric forming process and increase of the stability of RS property. The RS based on theelectron mechanism is gradually taken seriously by researchers and industrial circles, and becomes a newhot spot. Niobium doped strontium titanate （Nb:SrTiO₃） single crystal with a typical perovskite structurehave an excellent structure/chemical stability, and the carrier concentration and the electrical conductivityof the Nb:SrTiO₃single crystal can be conveniently controlled by changing the doping ratio or the defect.Compared with polycrystals, the single crystal have advantages of avoiding complex phenomena caused byhigh defect densities and crystal grain boundaries, preventing the multilayer behavior of the RS property,and conveniencing for the analysis of the resistive mechanism.The electrical-induced RS phenomenon in Nb:SrTiO₃single crystal Schottky junctions is mainlystudied in this thesis. Some meaningful results are obtained and manly comprise the following contents:The device for the assisted preparation of thin film electrode was invented. The device has theadvantages of simple structure, convenient operation, successful avoiding of the uneven electrode bondingand the uneven thickness of the thin film electrode in the preparation process of the thin film electrode, andpowerful guarantee for the preparation of the high-quality thin film electrode.The Schottky and Ohmic In/Nb:SrTiO₃junctions with good properties were prepared. TheIn/Nb:SrTiO₃Schottky junction having a good rectification property was prepared by sputtering, theIn/Nb:SrTiO₃Ohmic junction showing a low resistivity and a good linear I-V property was preparedthrough many different preparation technologies, and four In/Nb:SrTiO₃Ohmic junction preparation methods were provided.The RS behaviours were investigated detailly in the In/Nb:SrTiO₃devices with one or two Schottkyjunctions. A new RS phenomenon was found, and was named as an abnormal bipolar resistance switchingphenomenon. A dissymmetric diode model was used to explain the appearance of the abnormal bipolarresistance switching phenomenon. The carrier tapping/detrapping model was used to explain the RSmechanism through analyzing the s-In/Nb:SrTiO₃/o-In device and the electronic transport process of thes-In/Nb:SrTiO₃/o-In device. A low resistance state carrier tunneling effect was introduced to traditionaltrapping models.A multi-level planar resistive memory was designed. The planar structure of the memory canorganically combine the preparation process of the electrode and the forming process of RS layer, reducethe technological difficulty of the preparation of the device, and was in favor of the high density integrationof the device, and the planar resistive memory has the advantages of extremely-high stability,extremely-high repeatability and obviously-distinguished multi-level resistive states. A model wassupposed for the multi-level resistance states. The difference of the depletion layer width of the barrier wascaused by the difference in oxygen vacancy trapping carrier in different resistance states.A hernia lamp （polychromatic light） was used as a light source, and the optoelectric property and theRS property of the device are combined. The change in Schottky barrier causing RS was further determinedthrough eliminating the conducive fillament mechanism in a low resistance state by analyzing photovoltaicproperties of the In/Nb:SrTiO₃junction in different resistance states. The difference between the averageheight and the effective height of the Schottky barrier was clarified and the novel model of the Schottkybarrier change in different resistance states was provided. A RS model based on the depletion layer widthchange was provided through analyzing the C-V characteristic of the In/Nb:SrTiO₃junction. The oxygenvacancy migration in the trapping mechanism was discussed to further complete the carrier trapping/detrapping model.