Emerging memories: resistive switching mechanisms and current status

Abstract

The resistance switching behaviour of several materials has recently attracted considerable attention for its application in non-volatile memory (NVM) devices, popularly described as resistive random access memories (RRAMs). RRAM is a type of NVM that uses a material(s) that changes the resistance when a voltage is applied. Resistive switching phenomena have been observed in many oxides: (i) binary transition metal oxides (TMOs), e.g. TiO(2), Cr(2)O(3), FeO(x) and NiO; (ii) perovskite-type complex TMOs that are variously functional, paraelectric, ferroelectric, multiferroic and magnetic, e.g. (Ba,Sr)TiO(3), Pb(Zr(x) Ti(1-x))O(3), BiFeO(3) and Pr(x)Ca(1-x)MnO(3); (iii) large band gap high-k dielectrics, e.g. Al(2)O(3) and Gd(2)O(3); (iv) graphene oxides. In the non-oxide category, higher chalcogenides are front runners, e.g. In(2)Se(3) and In(2)Te(3). Hence, the number of materials showing this technologically interesting behaviour for information storage is enormous. Resistive switching in these materials can form the basis for the next generation of NVM, i.e. RRAM, when current semiconductor memory technology reaches its limit in terms of density. RRAMs may be the high-density and low-cost NVMs of the future. A review on this topic is of importance to focus concentration on the most promising materials to accelerate application into the semiconductor industry. This review is a small effort to realize the ambitious goal of RRAMs. Its basic focus is on resistive switching in various materials with particular emphasis on binary TMOs. It also addresses the current understanding of resistive switching behaviour. Moreover, a brief comparison between RRAMs and memristors is included. The review ends with the current status of RRAMs in terms of stability, scalability and switching speed, which are three important aspects of integration onto semiconductors.

Enhanced superconductivity in TiO epitaxial thin films

“…[1][2][3] Among various stable titanium oxides, the cubic metallic monoxide TiO is one of the very interesting materials because of the extremely wide homogeneity range, with oxygen content varying from about 0.80 to 1.30. [4][5][6][7] The electrical, optical, magnetic, and structural properties of bulk TiO have been widely investigated.…”

Phototunable Biomemory Based on Light‐Mediated Charge Trap

“…Prominent improvements in communication and information technologies generate the exponential growth of data‐storage device requirement due to the fundamental and critical functions of memory‐storage units for contemporary computing system 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. Analysts predict that total memory demand (i.e., 3 × 10 24 bits) will exceed commercial semiconductors supply in 2040 11, 12.…”

Giant electrode effect on tunnelling electroresistance in ferroelectric tunnel junctions

“…Therefore, it is critically important to investigate the redox-based resistive switching behaviour of our FTJs to clearly distinguish this mechanism from the FE-TER effect. It is known that an electroforming process is usually required to activate redoxbased resistance-switching phenomena in complex oxide materials 50 . Electroforming is generally achieved by applying high electric fields that can lead to soft breakdown of the insulating oxide layer.…”

“…Such fields induce the formation of localized (filamentary), defect-rich and structurally/chemically altered regions that have much higher electrical conductivity than the surrounding insulating matrix. It can be assumed that redoxbased resistance-switching effects result from physical/chemical ARTICLE phase transformations occurring somewhere along these defective, conducting filamentary paths, which can be brought forth by, for example, local Joule heating in combination with significant redistributions of mobile ionic species under electric field action 50 .…”

“…4 À 8 MV cm À 1 ) appear to be much higher than the ferroelectric coercive field of the studied BTO layer. This drastic difference may be attributed to high activation energies of the microscopic processes governing the redox-based resistive switching, such as the field-induced migration/re-distributions of anions and/or cations in oxide materials 39,50,51 . These energies probably exceed considerably the activation energy of ferroelectric domain nucleation at electric fields approaching the coercive field of our ultrathin BTO layer.…”