Promising new alloy for resistive switching memory

Sep 20, 2013
(A) This is an illustration of the RRAM array with each memory cell comprising of one filament (sandwiched between two electrodes). In comparison to the surrounding insulator matrix, a number of nano-filaments are formed within the bulk oxide. (B) This is a basic element of a RRAM cell. Control of the electrical field leads to different resistance states. (C) Localized formation of conductive filaments in a TiO2 thin film is shown. The left shows the conductivity map recorded by CAFM. The right shows the same current mapping in 3D. Credit: Yuanmin Du/National U.Singapore

Memory based on electrically-induced "resistive switching" effects have generated a great deal of interest among engineers searching for faster and smaller devices because resistive switching would allow for a higher memory density.

Researchers have tested a number of for their promise in resistive switching memories, and now a team of researchers in Singapore have demonstrated how conductive nano-filaments in amorphous (TiO2) thin films could be utilized for resistive switching device applications.

Yuanmin Du, Andrew Thye Shen Wee and researchers from the National University of Singapore and the Agency for Science, Technology and Research (A*STAR) of Singapore, describe their results in the journal AIP Advances.

How Resistive Switching Works

The basic idea of a resistive switching device is that an oxide, which normally acts as an insulator, can be transformed into a conductor, creating a nanoscale filament by using a sufficiently high voltage. With a RRAM (Resistive Random-Access Memory) device comprising of a single filament, two distinct resistance states ("1" and "0") can be obtained through a simple process of filament rupture and re-formation.

The conductivity of the oxide thin films can be adjusted by changing the deposition conditions. "During the measurements of the as-deposited amorphous TiO2 based resistive switching devices, it was found that the oxide thin films initially have good conductivity. This implies that a high initialization process is not required, as reported in many other switching devices using highly insulating oxide thin films," says Du. "The Conductive Atomic Force Microscopy (CAFM) experiments further confirmed that it is possible to form conductive filaments in oxide thin films through a localized transition by an ."

This research team applied both CAFM and KPFM (Kelvin Probe Force Microscopy), a unique approach that allowed the explanation of the observed resistive switching phenomena. Instead of treating filamentary and interfacial effects separately as done previously, both effects were integrated into one filament-interface model, which could help guide the design of RRAM based devices.

The evidence of high density and uniformly distributed nano-filaments implies that high-density memory cells could be made using such oxide thin films. Such materials are promising for future applications. The small dimension of the formed filament provides great advantages over current technology, as Du explains. "In addition to TiO2, we believe that many other oxides could also have the similar properties."

Explore further: Advancing resistive memory to improve portable electronics

More information: The article "The resistive switching in TiO2 films studied by conductive atomic force microscopy and Kelvin probe force microscopy" by Yuanmin Du, Amit Kumar, Hui Pan, Kaiyang Zeng, Shijie Wang, Ping Yang and Andrew Thye Shen Wee appears in the journal AIP Advances: dx.doi.org/10.1063/1.4818119

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PhysicistORnot
1.5 / 5 (8) Sep 24, 2013
What is memristor? What is the physical model behind? Is it really the missing circuit element? What is the difference between a filament switching memory and a memristor switching memory?

"Fundamental Issues and Problems in the Realization of Memristors" by Paul Meuffels, Rohit Soni. An interesting Arxiv paper by two Physicists.

PhysicistORnot
1 / 5 (2) Oct 09, 2013
The memristor is a concept defined by a set of mathematical equations firstly proposed by Leo Chua 1971. This needs to be further supported by a reasonable physical model. To the moment, it is still lacking. The known three circuit elements resistor, capacitor, inductor are all in accordance with the fundamental laws of physics. Does the memristor really exist? Many physicists have given the answers.

-the answers to my listed questions. I need to read more on this topic.

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