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Copper wires (small branching structures, above) grown by applying a voltage to copper-doped tungsten could be the key to a new type of ultradense memory.

Terabyte Nonvolatile Memory
A Flash ­alternative ­could store a ­terabyte of data

Source: “Bipolar and Unipolar Resistive Switching in Cu-Doped SiO2
Christina Schindler et al.
IEEE Transactions on Electron Devices 54: 2762-2768

Results: Using silicon and copper, researchers have made a new type of ­memory that stores information by harnessing negative and positive charges to assemble and disassemble nanoscale metallic wires. Each ­memory cell consists of two electrodes separated by an electrolyte doped with copper ions. When a cell is in the off state, little current passes from one electrode to the other. When a “writing” voltage is applied, the ions line up and form a filament that bridges the electrodes, markedly increasing current. Reversing the voltage causes the filament to dissolve.

Why it matters: The technology could lead to memory devices that hold more information, since each binary bit could be stored in wires just a couple of atoms thick. The new memory devices could be used to replace flash memory, eventually making it possible to store a terabyte of data on a cell phone or music player. Similar ionic memory devices have been made before in the lab, but they relied on more exotic materials. Chip makers might be more likely to consider adopting this new type of memory if they could use materials common in semiconductor manufacturing.

Methods: The researchers used standard techniques to deposit and pattern a tungsten electrode, a layer of silicon dioxide, and a copper electrode. By heating the layers to more than 600 ºC, the researchers then caused copper ions from the electrodes to diffuse into the silicon dioxide, forming the copper-doped electrolyte.

Next steps: The researchers need to optimize the performance of the memory cells and determine how many read-write cycles they can survive. To reach terabyte densities, it will be necessary to fabricate multilayer memory devices and store multiple bits of information on each wire; both feats should be possible with the new technology.

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Credit: Chakku Gopalan

Tagged: Computing, Materials

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