Bipolar Resistive Switching in Lanthanum Titanium Oxide and an Increased On/Off Ratio Using an Oxygen-Deficient ZnO Interlayer

Abstract

The present study pioneered an oxygen migration-driven metal to insulator transition Mott memory, a new type of nonvolatile memory using lanthanum titanium oxide (LTO). We first show the reset first bipolar property without an initial electroforming process in LTO. We used oxygen-deficient ZnO as an interlayer between LTO and a W electrode to clarify whether oxygen migration activates LTO as the Mott transition. ZnO oxygen deficiency provides oxygen ion migration paths as well as a reservoir, facilitating oxygen migration from LTO to the W electrode. Thus, including the ZnO interlayer improved oxygen migration between LTO and the W electrode, achieving a 10-fold increased on/off current ratio. The current research contributes to a better understanding of valence change Mott memory by exploring the LTO resistive switching mechanism and ZnO interlayer influences on the oxygen migration process.

Regulation of oxygen vacancy on behaviors of memristors based on amorphous ZnTiSnO films

“…Grain boundaries are defect-concentrated regions that provide fast migration channels for carriers such as oxygen ions or oxygen vacancies. 25,26 Excessive grain boundaries lead to increase leakage current and reduce device stability. 27 The XRD results of the a-ZnTiSnO films prepared under different oxygen pressures after variable temperature annealing are shown in Fig.…”

Comment on “Bipolar Resistive Switching in Lanthanum Titanium Oxide and an Increased On/Off Ratio Using an Oxygen-Deficient ZnO Interlayer”

“…No core electrons in an oxygen vacancy can absorb the incident X-ray photon. Hence, a photoelectron signal originating from a missing oxygen atom is not possible, not to mention such a high percentage of oxygen vacancy in the near stoichiometric or O-rich films in the samples produced by Wang et al 7 In addition, in the original proposal by Fan and Goodenough, the binding energy of O 1s electrons should vary with the vacancy concentration. 13 This was not shown though the intensity of 532 eV emission has changed a lot across different samples in the report by Wang et al Recent studies suggest that the 531 eV signal is simply the adventitious hydroxyls of water that are inevitably adsorbed on the metal oxides in ambient conditions.…”

“…As a consequence, a 10-fold increased ON/OFF current ratio was achieved. Wang and co-workers 7 observed the surface O 1s photoelectron spectroscopy peak in the energy range from 530 to 532 eV, and they attributed these peaks to the oxygen vacancy of the LTO film. The assignment of the O-vacancy energy is not appropriate.…”

“…Found with XPS, the initial LTO composition was La:Ti:O = 1.80(±0.02):1.93(±0.02):7.27(±0.02). 7 It is obvious that the resulting films are O-rich rather than O-deficient ones. This result should be due to incorporating ambient oxygen and water molecules.…”

“…As shown in Figure 1(a) and (b), the Ti 2p spectra are similar to the work reported by Wang and co-workers. 7 The Ti 2p peak can be deconvoluted into two twin peaks corresponding to Ti 3+ and Ti 4+ states. The Ti 4+ XPS spectrum peaks at around 458.9 and 464.7 eV, respectively, corresponding to the Ti 2p 3/2 and Ti 2p 1/2 spin−orbit doublets.…”