Characterization of mechanical, optical and structural properties of bismuth oxide thin films as a write-once medium for
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Characterization of mechanical, optical and structural properties of bismuth oxide thin films as a write-once medium for blue laser recording Martyniuk M.1, Baldwin D.2, Jeffery R.3, Silva K.K.M.B.D.1, Woodward R.C.4, Cliff J.5, Krishnan R.N.1, Dell J.M.1, and Faraone L1 1
School of Electrical, Electronic and Computer Engineering, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia 2
4Wave Inc., Sterling, VA, United States
3
Panorama Synergy Ltd, Balcatta, WA, Australia
4
School of Physics, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia 5
Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia
ABSTRACT We report on the preparation and characterization of crystalline bismuth oxide thin films via Biased Target Ion Beam Deposition method. A focused blue laser (405nm) is used to write an array of dots in the bismuth oxide thin film and demonstrate clear and circular recording marks in form of “bubbles” or “little volcanos” (FWHM ~500nm). Results indicate excellent static recording characteristics, writing sensitivity and contrast. The recording mechanism is investigated and is believed to be related to laser-induced morphology change. INTRODUCTION Bismuth oxide films have been demonstrated by a number of growth techniques, including reactive magnetron sputtering [1, 2, 3], Rapid thermal oxidation [4], air oxidized vacuum evaporation [5], Pulsed Laser deposition [6], and spray pyrolysis [7, 8]. Five separate crystalline polymorphs (D, E, J, G, Z) of Bi2O3 have been reported in the literature [8]. Additionally, two non-stoichiometric phases (Bi2O2.33 and Bi2O2.75) have also been reported [8]. The deposition technique and conditions have been shown to strongly affect the phase composition of the deposited Bismuth oxide material. The present work examines films of Bismuth oxide deposition using a relatively new technique, Biased Target Ion Beam Deposition (BTIBD). A number of interesting optical and electrical properties have been demonstrated in bismuth oxide. These properties include a high optical nonlinearity in optical fiber [9, 10], good photosensitivity in the ultraviolet wavelengths [3], an optical bandgap varying from 2eV to 3.96eV depending on the deposition technology [3], and an electrical conductivity, dependent of the mode of deposition, which can vary over five orders of magnitude [6]. The property of importance to the present work is the demonstrated sensitivity to writing by a blue light, demonstrated previously by Jiang et al. [1].
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Blu-ray media, players and recorders are fast replacing their DVD counterparts as the standard optical data storage format. According to the blu-ray specification, the media can contain up to 27 GB of data per recorded layer. To achieve this data density, the blu-ray player/recorder uses a 405 nm blue/violet laser, and a focusing lens with a numerical aperture of 0.85. In order to achieve low-cost blu-ray disk media, a lot
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