Resistance switching in oxides with inhomogeneous conductivity

Abstract

Electric-field-induced resistance switching (RS) phenomena have been studied for over 60 years in metal/dielectrics/metal structures. In these experiments a wide range of dielectrics have been studied including binary transition metal oxides, perovskite oxides, chalcogenides, carbon-and silicon-based materials, as well as organic materials. RS phenomena can be used to store information and offer an attractive performance, which encompasses fast switching speeds, high scalability, and the desirable compatibility with Sibased complementary-metal-oxide-semiconductor fabrication. This is promising for nonvolatile memory technology, i.e. resistance random access memory (RRAM). However, a comprehensive understanding of the underlying mechanism is still lacking. This impedes a faster product development as well as an accurate assessment of the device performance potential. Generally speaking, RS occurs not in the entire dielectric but only a small, confined region, which results from the local variation of conductivity in dielectrics. In this review, we focus on the RS in oxides with such an inhomogeneous conductivity. According to the origin of the conductivity inhomogeneity, the RS phenomena and their working mechanism are reviewed by dividing them into two aspects: interface RS, based on the change of contact resistance at metal/oxide interface due to the change of Schottky barrier and interface chemical layer, and bulk RS, realized by the formation, connection, and disconnection of conductive channels in the oxides. Finally the current challenges of RS investigation and the potential improvement of the RS performance for the nonvolatile memories are discussed.

Study on the Multi-level Resistance-Switching Memory and Memory-State-Dependent Photovoltage in Pt/Nd:SrTiO3 Junctions

“…The similar result was obtained by Hu et al [ 23 ]. Furthermore, a test method for Voc was reported by Shang et al [ 24 – 26 ]. According to this method, the Voc was further measured at LRS and HRS.…”

“…It is generally known that the photovoltaic (PV) effect is related to the internal electric field [ 22 – 26 ]. So, the PV effect is expected to be dependent on the memory states if the RS is mainly determined by the depletion layer near the metal and n-type STO interface.…”

Toward the complete relational graph of fundamental circuit elements

“…(2)) that -q relationship cannot be converted to v-i relationship in this case even though the coefficients defined in Eqs. (13-16) 8 have the same dimension of the resistance (Ohm). Clearly, their physical meaning is definitely different from that of the resistance; they are quantities reflecting the ability of device to convert q into  or vice versa.…”

Understanding the conductive channel evolution in Na:WO3−x-based planar devices

“…Many methods have so far been used to detect the conductive channels, such as scanning probe microscopy, [9][10][11][12] in situ transmission electron microscopy, [13][14][15][16][17][18][19][20][21] photo-emission electron microscopy, 22 X-ray absorption spectroscopy, 23,24 scanning electron microscopy, 25 and optical microscopy. [26][27][28][29] For the observed channel geometries, the dendritic shape is one of the typical configurations. The dendritic channels are usually metallic caused by reduction of cations (such as Ag + , Cu + ).…”