The Research On Resistive Switching Performance And Mechanism In ZnO And V₂O₅Thin Films

Applying an electric field on the metal electrode/insulator (orsemiconductor)/metal electrode sandwiched structures, theresistance of the device will change reversibly including nonvolatileresistive switching and volatile resistive switching (Thresholdswitching). Nonvolatile resistive switching means that high and lowresistance states can keep after removing voltage, but volatileresistive switching signifies that low resistance state can not keepand removes back to the high resistance state after removing voltageor applying a small voltage. Non-volatile resistive switchingcharacteristics can be used as non-volatile memory also known asresistive random access memory (RRAM), RRAM will become anext-generation promising candidate because of its simple structures,nondestructive read, high read and write speed, high stability, lowpower-consumption and compatibility with CMOS process. Volatileresistive switching characteristics can be used as selective device, electric switching and lightning protection system. Unfortunately, RSmechanism has not been well understood and has a lot of controversy.Therefore, it is important and meaningful to figure out themicro-mechanism. The work presented in the dissertation is focusedon the following two parts.(1) As an integrated and important part of resistive switchingdevice structures, intrinsic properties (electronegativity and ionicradius) and Interfacial state of electrode metals must have a greatinfluence on the resistive switching performance. This part of thework, by using typical electrodes (Pt, Au, Ni, Cu, Ag) and changingdevice structure, conducted that how electrode material andmicrostructure can affect different parameters such as high resistive&low resistive resistance values, set and reset voltage and formingvoltage. This part of content provides essential information for betterunderstanding the switching mechanism of zinc oxide based devices,and benefits the rational selection of proper electrode metal for thedevice performance optimization.(2) V2O5volatile resistance switching behavior was found for thefirst time, and intrinsic properties of electrode metals have a greatimpact on the resistive switching performance. According to themetal electrode intrinsic attributes, electrode can be devided into twogroups (inert electrode and active electrode). When using inert electrode, V2O5film has volatile resistance behavior resulting fromphase change of V2O5film. At this point, intrinsic physical propertiesof V2O5film, under the electric field, can be reflected; with activeelectrode being used, V2O5film performs for non-volatile resistanceswitching behavior induced by electrode atomic diffusion to formconductive channels under electric field. These channels mask theV2O5intrinsic physical properties and make device show thenon-volatile resistance characteristic.Furthermore, because of V having more than one valance and thedifferent valence inevitably accompanies with different physicalproperties. Moreover, Energy difference between different valence issmaller, so, it is easy to produce the redox reaction and make valanceof V change in the V2O5film. Due to different valence stateaccompanying with different resistance state and color, a solid-statedevice which possesses resistance and color switching at the sametime can be achieved for the first time.