Anodic Oxidation as a Means to Produce Memristive Films

Abstract

ristive characteristic actually observed in a metal/oxide/metal device built with Pt and TiO 2 (5). The memristive behavior of TiO 2 is based on the presence of oxygen vacancies moving forward and backward across the electronic barrier at the metal/ oxide interface, generally through the formation of an oxygen vacancy filament, which results in changes to oxide resistance (6-9). The existence of such a filament has already been proved both experimentally by applying microscopy-based techniques, and through modeling (10-14). This research study presents the technique of anodic oxidation as a means to produce metal oxides with added functionalities, specifically a memristive behavior, with a special focus on titanium, niobium and tantalum oxides (15). This technique can lead to the controlled production of oxide films on valve metals, and to the tuning of growth kinetics and oxide properties as a function of process parameters. Controlling electrochemical parameters (cell voltage, electrolyte composition, anodizing time) defines the oxide thickness, morphology, chemical and structural composition (15-17), which in turn is responsible for titanium surface properties such as corrosion resistance, insulation or biocompatibility (18, 19). Anodizing is a cheap, room-temperature alternative to physical and chemical fabrication methods typical of the electronics industry that are currently applied to memristor production. Furthermore, anodizing has already been demonstrated as suitable for producing memristive TiO 2 films (11, 20).

Memristive Anodic Oxides: Production, Properties and Applications in Neuromorphic Computing

“…This may have as well a role in the degradation of resistive switching. Other compact oxide films showing memristive behavior were then grown on titanium as well as on niobium and tantalum: anodizing in diluted phosphoric acid at 25 V, corresponding to an oxide thickness of approximately 60 nm, was found to allow the achievement of the best switching behavior [83].…”

“…In all abovementioned cases, the anodic oxides showed parameters compatible with requirements identified for resistive switching materials: high R off /R on ratio (> 10, with best values in the order of 80), set/reset values lower than 1 V and possibility to obtain multilevel switching [81]. Moreover, in several works, the oxides produced were electroforming-free: this can be ascribed to the anodic oxidation process itself, which is known to generate non-stoichiometric oxides, therefore the content of oxygen vacancies natively present in the oxide is already sufficient to produce the switching [49,83,84].…”

Solution-processed, low voltage tantalum-based memristive switches

“…Metal oxide dielectrics have drawn a lot of attention in recent years due to their use in the fabrication of high performance thin film capacitors (TFCs) [1], low voltage thin film transistors (TFTs) [2], and memristor devices [3]. However, the next generation of thin film electronic devices and systems will require reduced power consumption and the development of dielectric materials that can be inexpensively deposited from solution on large areas as a thin film is urgently needed [4].…”

Electrochemical Anodizing Treatment to Enhance Localized Corrosion Resistance of Pure Titanium

“…The thickness of the natural titanium oxide layer, and consequent resistance to corrosion, may be increased by using an electrochemical anodizing treatment. An anodic polarization of several volts, up to 100 V, is applied on the titanium surface in a proper electrochemical bath, promoting the increase of the oxide layer from about 10-20 nm, up to 250-300 nm (14–15–16–17). At voltages higher than 100 V, the anodizing treatment causes the instauration of microarcs in the insulating oxide layer; this regime is called anodic spark deposition (ASD) or plasma electrolytic oxidation (PEO).…”