IBM EXPLORING NEW STORAGE TECHNOLOGY

Magnetic recording is the predominant data storage technology today and continues to make rapid advances in data density. In the future, however, fundamental physical phenomena, such as bit instability due to superparamagnetism, may be encountered that limit the achievable data density. At the IBM Almaden Research Center, researchers are exploring technologies that may allow data densities well beyond the current gigabit per square inch density of magnetic recording. Techniques that have been investigated over the past several years include: scanning tunneling microscopy, charge storage in nitride-oxide-silicon (NOS) structures, and near field optical storage based on solid immersion lenses (SIL). Present projects include atomic force microscope data storage and holographic data storage.

Scanning tunneling microscopes (STM) can readily write and read atomic scale surface features. This density is roughly equivalent to a million gigabits per square inch. A famous example of atomic scale writing is the IBM logo spelled out with individual xenon atoms using a low temperature STM.

Under more practical conditions of room temperature and atmospheric pressure, atomic-force microscopy (AFM) provides a means to write and read information at densities between 40 and 300 gigabits per square inch. This method relies on using a sharp tip mounted on a micromechanical cantilever Data is written thermomechanically by heating the tip while it is in contact with a plastic disk substrate. The combination of heating and tip pressure causes a small indentation to be formed in the surface of the plastic. (Examples of thermomechanical writing.) Alternatively, read-only data can be mastered at densities up to 100 gigabit per square inch by using a photopolymer-molding process. Readback of the data is achieved by monitoring the motion of the cantilever as the tip rides over the tiny indentations on the disk.