Resistive switching phenomena: A review of statistical physics approaches

Abstract

Resistive switching (RS) phenomena are reversible changes in the metastable resistance state induced by external electric fields. After discovery $50 years ago, RS phenomena have attracted great attention due to their potential application in next-generation electrical devices. Considerable research has been performed to understand the physical mechanisms of RS and explore the feasibility and limits of such devices. There have also been several reviews on RS that attempt to explain the microscopic origins of how regions that were originally insulators can change into conductors. However, little attention has been paid to the most important factor in determining resistance: how conducting local regions are interconnected. Here, we provide an overview of the underlying physics behind connectivity changes in highly conductive regions under an electric field. We first classify RS phenomena according to their characteristic current-voltage curves: unipolar, bipolar, and threshold switchings. Second, we outline the microscopic origins of RS in oxides, focusing on the roles of oxygen vacancies: the effect of concentration, the mechanisms of channel formation and rupture, and the driving forces of oxygen vacancies. Third, we review RS studies from the perspective of statistical physics to understand connectivity change in RS phenomena. We discuss percolation model approaches and the theory for the scaling behaviors of numerous transport properties observed in RS. Fourth, we review various switching-type conversion phenomena in RS: bipolarunipolar, memory-threshold, figure-of-eight, and counter-figure-of-eight conversions. Finally, we review several related technological issues, such as improvement in high resistance fluctuations, sneak-path problems, and multilevel switching problems. V

Research Update: Fast and tunable nanoionics in vertically aligned nanostructured films

“…36 The size of conducting channels ranges from a few to a few tens of nanometer. 39,40 The connection and rupture of the channels are governed by a percolating behavior, 20,25,41,42 inducing highly random device performance. Furthermore, huge current overshot occurs during the electroforming process, sometimes burning the ionic memory devices.…”

“…A decrease of the film thickness into the nanoscale regime has boosted the development of ionic memory devices. [19][20][21][22][23][24][25][26]30,35 As shown in Figure 1(c), the device structures are usually composed of oxide thin films (or semiconductor thin films) with either novel metal (e.g., Au and Pt) electrodes or mobile metal (e.g., Ag or Cu) electrodes. However, most as-grown films are not sufficient to display electric-field-induced RS phenomena.…”

“…Next-generation memory devices based on resistive switching (RS) phenomena have been demonstrated using ionic motion in semiconductors. [19][20][21][22][23][24][25][26] When an electric field is applied, ions move toward one electrode, and accumulate and form conducting channels, resulting in a low-resistive state of the device. When an electric field with opposite polarity is applied, the ions in the channels move back to the other electrode; therefore, the channels are dissolved and ruptured, resulting in a high-resistive state of the device.…”

Resistive Switching in Stabilized Zirconia Films Studied by Conductive Atomic Force Microscopy

“…The effect of RS consists in a reversible change of the resistance of a thin dielectric film sandwiched between two conductive electrodes under the electric voltage applied between the electrodes. Today's understanding of the RS mechanism in the transition metal oxides is based on a con-cept of the motion of the oxygen vacancies (V O s) in the electric field between the electrodes [2]. The V O s form the conductive filaments growing through almost whole insulator layer (the forming process) and, thus, shortcut the electrodes.…”

Quantum point contacts and resistive switching in Ni/NiO nanowire junctions

“…After an initial electroforming process, application of an electric field switches the device's electrical conductivity between a LRS and a HRS. Devices based on transition metal oxides, such as NiO x , 2-4 TiO x , 4,5 HfO x , 6 Ta 2 O 5 , 5,7,8 and SiO x , 9,10 have all demonstrated resistive switching with some devices exhibiting resistance ratios and cycling endurances sufficient for many computational memory applications. 9,[11][12][13][14][15][16] Resistive switching in oxide-based systems is thought to arise from the rupture and reformation of nanoscale conducting filaments that span the oxide.…”