Characteristic electroforming behavior in Pt/TiO2/Pt resistive switching cells depending on atmosphere

Abstract

Electroforming effects on the composition, structure, and electrical resistance of Pt/ TiO 2 / Pt switching cells are investigated. The correlation between the electroforming procedure and the resulting bipolar switching behavior is discussed. The dependence of electroforming behavior on atmosphere is also identified, from which we define symmetric or asymmetric electroforming. The symmetry of electroforming is a key factor determining the resulting bipolar switching characteristics. From the experimental results we suggest a possible mechanism for electroforming in Pt/ TiO 2 / Pt in terms of the formation of oxygen gas and vacancies in the vicinity of the anode.

Impact of the electroforming process on the device stability of epitaxial Fe-doped SrTiO3 resistive switching cells

“…This is a strong indication that the electroforming pro- cess is a local phenomenon, e.g., due to the formation of a conducting filament. These findings are consistent with results found in TiO 2 devices by Jeong et al 9 and Yang et al 20 …”

“…16 Szot et al 17 demonstrated that, using SrTiO 3 single crystals, the electroforming process removes oxygen ions from the crystal lattice which becomes evident by the appearance of gas bubbles under the anode. The evolution of oxygen gas bubbles was also observed in thin film Pt/ TiO 2 / Pt samples by Jeong et al 9 and Yang et al 10 Conductive atomic force microscopy ͑LC-AFM͒ measurements performed on SrTiO 3 single crystals 17 and epitaxial thin films 18,19 indicated a laterally confined and filamentary current transport within the material. The conducting filaments were attributed to extended defects such as edge dislocations.…”

“…This finding is different to, e.g., Pt/ TiO 2 / Pt devices which can be formed with different polarities. 9,10 It is well known from point defect chemistry arguments 27,28 that Nb:STO, i.e., n-conducting donor doped STO, exhibits a negligible amount of oxygen vacancies under normal conditions. Thus, Nb:STO cannot really act as a sink for oxygen ions so that the forming process does not work in the opposite ͓Pt͑−͔͒ direction.…”

“…9 This has been facilitated by the effect of high electric fields and local Joule heating. 10 Changes in the oxygen vacancy concentration bring about changes in the conductivity due to the so-called self-doping effect.…”

Nonvolatile Resistive Switching inPt/LaAlO3/SrTiO3Heterostructures

“…The migration of charged oxygen vacancies is the mostly cited mechanism responsible for the RS behavior observed in a wide range of sandwich-type oxide-based devices [34,[74][75][76][77][78]. However, as proposed by Liu and co-workers, the trapping or detrapping of electrons in the defect-derived quasiconduction band in 150-nm-thick LAO films can lead to the overlap of wave functions and the reversible insulator-metal transitions [68].…”