Improving Your Memory
A faster, cheaper, smaller way to make computers remember
CONTEXT: Which takes longer, walking to and from the coffeepot, or starting up a computer? The answer, sadly, is often the latter. That’s because the most common computer memory technologies, DRAM and SRAM, are “volatile,” meaning they require power to retain data and must reload information when restarted. Other memory technologies, such as the flash RAM found in today’s digital cameras, cell phones, and PC cards, can hold data without power, but they read and write information too slowly to be used for computing purposes. Researchers at the University of California, Los Angeles, have recently designed a new form of fast, cheap memory, based on organic materials and nanoparticles, that seems to overcome many of these limitations.
METHODS AND RESULTS: A memory device is essentially a system that can switch between distinct states, like the “on” or “off” states of a transistor. Jianyong Ouyang and colleagues built a device from a thin film of material that switches between being more or less electrically conductive. They created a 50-nanometer-thick polymer film loaded with gold nanoparticles and an electron-rich carbon-based molecule, then sandwiched the film between two metal electrodes. When electrically grounded, the film can barely conduct a current. Apply enough voltage between the electrodes, however, and electrons move from carbon to gold, raising the conductivity through the sandwich by a factor of 10,000.
The transition occurs in less than 25 nanoseconds, the limit of what the team could detect; the states are stable even when the power is off and can be switched back and forth repeatedly. The polymer film is easy and cheap to make, and unlike silicon-based memory, these polymer-based devices could easily be built up in layers, enabling extremely high densities in a small volume.
WHY IT MATTERS: This research stands out from fierce competition because the cheap and simple methods reported yielded excellent performance, surpassing that of flash RAM and rivaling conventional computer memory.
But the streets of Silicon Valley are littered with the remains of engineers and investors who have tried and failed to break into the memory market. Ouyang and colleagues eventually must show that their memory device is reliable and can be manufactured on an industrial scale. Nonetheless, this new approach should be a contender in the battle for low-cost, high-density memory in digital cameras, cell phones, and personal computers.
SOURCE: Ouyang , J., et al. 2004. Programmable polymer thin film and non-volatile memory device. Nature Materials 3:918-922.