Hysteretic current–voltage characteristics and resistance switching at an epitaxial oxide Schottky junction SrRuO3∕SrTi0.99Nb0.01O3

Abstract

Transport properties have been studied for a perovskite heterojunction consisting of SrRuO3 (SRO) film epitaxially grown on SrTi0.99Nb0.01O3 (Nb:STO) substrate. The SRO/Nb:STO interface exhibits rectifying current-voltage (I-V ) characteristics agreeing with those of a Schottky junction composed of a deep work-function metal (SRO) and an n-type semiconductor (Nb:STO). A hysteresis appears in the I-V characteristics, where high resistance and low resistance states are induced by reverse and forward bias stresses, respectively. The resistance switching is also triggered by applying short voltage pulses of 1 µs -10 ms duration. 73.40.-c, 73.30.+y, 77.90.+k Recently, reversible resistance switching between two or multilevel resistance states has been found to take place by short voltage pulses at room temperature in capacitor-like devices composed of a wide variety of insulating perovskite oxides such as manganites, 1,2,3 titanates, 4 and zirconates 5 sandwiched between two metallic electrodes. This resistance switching attracts considerable attention due to the potential for device application such as resistance random access memories (RRAM). 6 The origin of resistance switching, however, is still an open question. One of the possibilities is the bulk effect 1,4,5,6 that a phase transition of perovskite takes place between insulating and conducting states, similar to the breakdown of charge-ordered insulating state in manganites induced by electric-field at low temperature. 7,8,9 The other is the interface effect, where voltage pulses reversibly alter the nature of potential barrier formed in the insulating (or semiconducting) perovskite in contact with metallic electrodes. 2,3 We have recently shown that the resistance switching occurs at a Ti/Pr 0.7 Ca 0.3 MnO 3 (PCMO) interface, 3 which exhibits Schottky-like currentvoltage (I-V ) characteristics, where Ti and PCMO can be regarded as a shallow work-function metal and a p-type semiconductor, respectively. A possible origin for the resistance switching is attributed to the change in Schottky barrier height (or width) by trapped charge carriers at the interface states. However, non-epitaxial structure and chemically incompatible materials combination make it difficult to characterize the transport properties and interface electronic structure in detail.In the present study, we have investigated the transport properties of a heteroepitaxial perovskite oxide interface consisting of SrRuO 3 (SRO) deposited on (001) SrTi 0.99 Nb 0.01 O 3 (Nb:STO) single crystal substrate. The SRO/Nb:STO interface exhibits rectifying Schottky-like I-V characteristics with large hysteresis and the resistance can be changed by applying pulsed-voltage stress.Epitaxial SRO thin films (100 nm) were grown on (001) Nb:STO single crystal substrates by a pulse laser deposition technique. Typical growth conditions were a substrate temperature of 700 • C and an oxygen pressure of 100 mTorr. After the deposition, the films were in-site annealed at 400 • C for 30 minutes under an oxygen pressure ...

High-quality all-oxide Schottky junctions fabricated on heavily doped Nb:SrTiO3substrates

“…These systems show electroresistive ͑ER͒ switching that is believed to arise from the change in Schottky barrier height and/or width by trapped charge carriers at the interface states. 1,2 Unlike ER switching observed in many oxide films, in which an electric field generates conductive filamentary paths, 3,4 the interface-type switching is expected to be strictly confined at the junction interface. As a consequence, the latter is more promising for highdensity integration.…”

Ab initioand photoemission study of correlation effects in SrRuO3thin films

“…1 Since this perovskite is chemically stable, exhibits excellent electrical conductivity, and has a good lattice matching with various functional oxides, it is the material of choice for electrodes, heterojunctions, and multiferroic devices. [2][3][4][5][6][7] One of the most important questions concerning the physics of SrRuO 3 is a significance of correlation effects and how physical properties of the material are impacted by correlated movement of electrons. 8 Due to highly extended nature of 4d orbitals, it is natural to assume that correlation effects in 4d transition metal oxides should be weak.…”

Improved endurance behavior of resistive switching in (Ba,Sr)TiO3 thin films with W top electrode

“…[7][8][9] Several models have been proposed to explain the mechanism. [10][11][12] Even though the exact microscopic mechanisms are still under controversial discussion, there exists a general agreement that the migration of oxygen ions under an applied electric field plays a key role. 13 Since oxygen vacancies work as the donors in oxide-based semiconductors, the field driven local accumulation or depletion of oxygen vacancies may be identified with the two resistance states.…”