Silver shows new potential for optical data storage

17 Jun 2002

Nanoclusters of 2 to 6 silver atoms could be the basis for a new method of optical data storage. Scientists at Georgia Institute of Technology in the US have demonstrated that the atoms, gathered as a thin film of silver oxide nanoparticles, develop an ability to fluoresce after being illuminated with blue light (of a wavelength of less than 520 nm). This exposure partially converts particles near the surface to clusters of photoactivated silver atoms. When exposed next to green light (of a wavelength of more than 520 nm), the particles fluoresce strongly, emitting red light that is visible to the naked eye.

Led by Robert Dickson, the researchers used the technique to achieve binary optical storage of simple geometric shapes at room temperature. However, there is potential for higher-dimension optical storage, thinks Dickson, because when observed under a microscope the silver particles were seen to emit in green, then red, and then yellow wavelengths. "Not only are you generating fluorescence, you presumably are also changing the size and/or geometry of the cluster," he suggested. These multicolor emissions could allow storage of more than one bit of information in each data point, and, if arranged in a three-dimensional matrix, could offer a very dense storage medium.

So far, images stored on the film have been read non-destructively by green light after two days. Further study is required to determine how long storage could persist and to obtain a full understanding of how the particles fluoresce.