Role and Optimization of the Active Oxide Layer in TiO₂‐Based RRAM

Abstract

TiO2 is commonly used as the active switching layer in resistive random access memory. The electrical characteristics of these devices are directly related to the fundamental conditions inside the TiO2 layer and at the interfaces between it and the surrounding electrodes. However, it is complex to disentangle the effects of film “bulk” properties and interface phenomena. The present work uses hard X‐ray photoemission spectroscopy (HAXPES) at different excitation energies to distinguish between these regimes. Changes are found to affect the entire thin film, but the most dramatic effects are confined to an interface. These changes are connected to oxygen ions moving and redistributing within the film. Based on the HAXPES results, post‐deposition annealing of the TiO2 thin film was investigated as an optimisation pathway in order to reach an ideal compromise between device resistivity and lifetime. The structural and chemical changes upon annealing are investigated using X‐ray absorption spectroscopy and are further supported by a range of bulk and surface sensitive characterisation methods. In summary, it is shown that the management of oxygen content and interface quality is intrinsically important to device behavior and that careful annealing procedures are a powerful device optimisation technique.

Role of Oxygen Deposition Pressure in the Formation of Ti Defect States in TiO2(001) Anatase Thin Films

“…7,8 Thin films of TiO 2 are also the subject of interest for photovoltaic applications 9 or resistive switching memory devices. 10,11 TiO 2 is present in nature in three different polymorphs: rutile, anatase, and brookite. Although the most stable form under ambient conditions is rutile, the quasi-metastable anatase TiO 2 is considered to be potentially more relevant for energy-related applications.…”

Memristive TiO2: Synthesis, Technologies, and Applications

“…Annealing in reducing atmospheres affects the concentration of charged point defects and thus the resistive switching. Despite many experimental studies, including the post-fabrication thermal annealing stage (typically at 400–600°C) under vacuum (Schmidt et al, 2015 ), nitrogen (Seo et al, 2011 ; Cortese et al, 2016 ; Regoutz et al, 2016 ), argon (Nelo et al, 2013 ), or N 2 + H 2 (4–5%) gas mixtures (Yang et al, 2008 ; Miller et al, 2010 ), only a few studies have systematically addressed the effects of thermal treatment under various annealing atmospheres on the resistive switching behavior of TiO 2 memristive devices (Lai et al, 2013a , b ; Nelo et al, 2013 ).…”

Tuning conductivity and magnetism of CuFe2O4via cation redistribution

“…[1][2][3] The ion migration, especially anion (e.g., O 2À ions) redistribution, is vital to the nonvolatile resistive switching (RS) properties of oxide thin lms, which have been extensively studied by many researchers. [4][5][6] Cation redistribution in oxide materials is also important due to tunable magnetic and optical properties beyond the RS effect. Spinel ferrites are among those oxide materials with tunable magnetism via cation redistribution.…”