title: Synthesis of a metal oxide with a room-temperature photoreversible phase transition.
abstract: 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 Ti(3)O(5), lambda-Ti(3)O(5). lambda-Ti(3)O(5) 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 lambda-Ti(3)O(5) trapped at a thermodynamic local energy minimum. Light irradiation causes reversible switching between this trapped state (lambda-Ti(3)O(5)) and the other energy-minimum state (beta-Ti(3)O(5)), both of which are persistent phases. This is the first demonstration of a photorewritable phenomenon at room temperature in a metal oxide. lambda-Ti(3)O(5) 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).
authors.affiliation: Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. ohkoshi@chem.s.u-tokyo.ac.jp
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Ohkoshi
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Tsunobuchi
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Matsuda
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Hashimoto
authors.forename: Asuka
authors.initials: A
authors.lastname: Namai
authors.forename: Fumiyoshi
authors.initials: F
authors.lastname: Hakoe
authors.forename: Hiroko
authors.initials: H
authors.lastname: Tokoro
mesh_terms: D018360:Crystallography, X-Ray; D008968:Molecular Conformation; D053758:Nanoparticles / Q000737:chemistry; D010087:Oxides / Q000138:chemical synthesis* / Q000737:chemistry; D044367:Phase Transition; D055668:Photochemical Processes; D011789:Quantum Theory; D013696:Temperature; D013816:Thermodynamics; D014025:Titanium / Q000737:chemistry*
chemical_list: D010087:Oxides; D014025:Titanium