A Japanese research team have discovered a material that could be used to make ultra-high density optical discs with data storage capacity thousands of times greater than a DVD.
Photoinduced phase-transition materials, such as chalcogenides, spin-crossover complexes, photochromic organic compounds and charge-transfer materials, are generally interesting among scientists because of their application to optical data storage. Professor Shin-ichi Ohkoshi and his colleagues from the University of Tokyo reported today that they have developed a material which transforms from a black-colour metal state that conducts electricity into a brown semiconductor when hit by light.
The scientists achived a photoreversible metal?semiconductor phase transition at room temperature with a unique phase of a Titanium oxide (Ti3O5) material, λ-Ti3O5. The thermodynamic analysis suggests that the photoinduced phase transition originates from a particular state of λ-Ti3O5 trapped at a thermodynamic local energy minimum. Light irradiation causes reversible switching between this trapped state (λ-Ti3O5) and the other energy-minimum state (β-Ti3O5), both of which are persistent phases.
A material that changes colour with light can be used in storage devices as colours reflect light differently to contain different information.
This is the first demonstration of a photorewritable phenomenon at room temperature in a metal oxide. The scientists claim that the λ-Ti3O5 satisfies the operation conditions required for a practical optical storage system (operational temperature, writing data by short wavelength light and the appropriate threshold laser power).
Professor's Ohkoshi team succeeded in creating the material in particles measuring a few nanometers in diameter. If As these particle is used, the new disc could hold more than 1,000 times as much information as a Blu-ray disc. Of course, matching data-writing and reading equipment will be required.
Titanium oxide's market price is about one-hundredth of the germanium-antimony-tellurium that is currently used in rewritable Blu-ray discs and DVDs. As a result, using the new Titanium oxide material could also mean cheaper optical discs.
However, it is not clear whether we will see a disc made of the new material anytime soon. Professor Ohkoshi said that he would start talks with private-sector companies for commercialisation, as he was quoted to say by the Associated Press.