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(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. Image Credit: Yuanmin Du/National U.Singapore
A research team from the National University of Singapore has shown how nanostructures in amorphous titanium dioxide could be used for the next generation of electronic device memory.
The team found that titanium dioxide can be altered to create pioneering memory cells using ‘resistive random-access memory’ (RRAM, or ReRAM).
RRAM is one of several new techniques that are being developed for storing data in electronic devices such as laptops and smartphones.
It is being touted as an alternative to commonly used memory formats such as flash, which is commonly used in USB sticks and digital cameras. However, compared to flash and similar memory types, RRAM can be used in low power applications and also allows for a higher memory density.
Creating RRAM involves ‘resistive switching’ of materials, which is involves taking an insulating dielectric material, such as TiO2, and ‘forcing’ it to conduct electricity, providing enough voltage is applied. This leads to localized formation of conductive filaments in the TiO2 thin film.
This new research is unique because it integrates both CAFM and KPFM techniques, and separate effects were combined into one filament-interface model. One of the co-authors of a paper outlining the recent work, Yuanmin Du, describes the benefits of using titanium dioxide in more detail below.
"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 electrical breakdown initialization process is not required, as reported in many other switching devices using highly insulating oxide thin films."
"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 electrical field."
Several other materials have also shown resistive switching effects, including perovskites and solid-state electrolytes, as well as with other oxides.
"In addition to TiO2 we believe that many other oxides could also have similar properties." - Yuanmin Du
The work could have major benefits for manufacturers wanting producing faster and smaller electrical devices, as it allows for a higher memory density than traditional methods. A number of companies are currently working on developing RRAM commercially.
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In the future, RRAM could be applied in a wide range of electrical devices that save information, from tablets to laptops. Image credit: photos.com.
Original source: American Institute of Physics
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