The material transforms from a black metal state that conducts electricity into a brown semiconductor when hit by light, according to Shin-ichi Ohkoshi, chemistry professor at the University of Tokyo.
His team has succeeded in creating the material in particles measuring five-to-20 nanometres (a five-billionth to 20-billionth of a metre) in diameter. If the smallest particle is used, the new disc could hold more than 1,000 times as much information as a Blu-ray disc, provided that matching data-writing and reading equipment are developed. A single-layer Blu-ray disc can hold five times as much data as a conventional DVD.
Prof Ohkoshi said it was not known when a disc with the material would be manufactured and put to practical use, adding that he would start talks with private-sector companies for commercialisation. Titanium Oxide is currently used in things like white paint.
Photoinduced phase-transition materials, such as chalcogenides, spin-crossover complexes, photochromic organic compounds and charge-transfer materials, are of interest because of their application to optical data storage. Here we report a photoreversible metal–semiconductor phase transition at room temperature with a unique phase of Ti3O5, λ-Ti3O5. λ-Ti3O5 nanocrystals are made by the combination of reverse-micelle and sol–gel techniques. 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. This is the first demonstration of a photorewritable phenomenon at room temperature in a metal oxide. 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).