In many ways, hard drives are the bane of our existence. Although they can store plenty of data, data access remain (relatively) slow. Furthermore, the moving parts make hard drives vulnerable to various types of failure. Nevertheless, in the past 40 years, they've been irreplaceable because it is very hard to make nonvolatile memory as cheaply as a hard drive. Now, some new research on nanowires may point the way towards a new kind of high-density, nonvolatile storage.

In the past few years, researchers have begun exploring phase changes as a method for storing data. Phase changes are currently used for rewritable CDs and DVDs, so this isn't exactly a new idea. In these storage media, discrete points in a crystalline material are heated and rapidly cooled to make the material amorphous. This change in the physical structure creates a sufficiently large change in reflectivity that ones and zeros can be distinguished by shining a laser beam onto the disk.

Using a superficially similar approach, researchers at the University of Pennsylvania have constructed a memory device based on a nanowire. The information is stored in the physical structure of the material, and the physical structure is altered by pulses of current. The research, published in Nature Nanotechnology, details the growth of single crystal wires made from a semiconductor alloy. It was found that a sufficiently short and intense burst of current caused the material to lose its crystalline structure, at which point the material became amorphous and highly resistant. A second, longer, lower amplitude burst of current would allow the crystalline structure to form again. The research demonstrates that these memory gates last for more than 105 operations and have read/write times between 50 to 100ns, which is certainly competitive with hard drives (though RAM is still much faster).

You won't find devices based on this tech in your store within the next year, though, or even in the next five years. The problem is that growing these wires is difficult, and growing them in a controlled manner is nearly impossible. Although the researchers suggest several ways through which more controlled growth and placement may be obtained, it is clear that simply making the raw material for these devices is the big unsolved problem. In fact, this is the big unsolved problem with almost everything associated with nanotechnology.

Nature Nanotechnology, 2007, DOI: 10.1038/nnano.2007.291