The latest entry into the nano-enabled nonvolatile memory sweepstakes comes from a team of researchers from Taiwan and the University of California Berkeley. The multinational research team claims it has developed a new electronic memory using silicon quantum dots that is 10-100 times faster in writing and erasing data than charge-storage memory.
While nanoribbons promise greater storage density and carbon nanotubes look to be able to make resistive random-access memory and phase-change memory realities, it seems the metal-gate silicon quantum-dot nonvolatile memory the researchers described in Applied Physics Letters is just ultrafast. There doesn’t seem to be any information on what kind of storage density the memory is capable of.
Nonetheless the researchers believe that metal-gate structures—like the one that was used in this memory—are on a path to realizing nanoscale complementary metal-oxide-semiconductor (CMOS) memory. "Our system uses numerous, discrete silicon nanodots for charge storage and removal. These charges can enter (data write) and leave (data erase) the numerous discrete nanodots in a quick and simple way," explains Jia-Min Shieh, a researcher with the National Nano Device Laboratories in Taiwan.
The memory is designed around a non-conducting material in which discrete quantum dots have been fixed. Each one of these quantum dots serves as a single memory bit. After the quantum dots have been affixed to the non-conducting material, a metallic layer is laid on top, which serves as the metal gate providing the “on” and “off” function of the transistor.
The extreme speed of the device is the result of using ultra-short bursts of green laser light to stimulate specific areas of the metal layer. What the researchers discovered was that the green laser was able to create gates over each individual quantum dot.
It’s not clear what kind of commercialization track this research may be on, but the researchers seem to feel that because it’s compatible with CMOS processes commercial aspirations should be achievable.
"The materials and the processes used for the devices are also compatible with current main-stream integrated circuit technologies," explains Shieh. "This technology not only meets the current CMOS process line, but can also be applied to other advanced-structure devices."
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.