TeOx thin films for an optical disc memory

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Abstract
Tellurium suboxide thin films TeOx were found to change in refractive index and extinction coefficient on thermal or optical heating, with accompanying changes in the reflectivity and transmission. The preparation method and thermal or optical properties of the TeOx thin films were investigated to obtain a stable and highly sensitive optical disc memory. A two‐source evaporation method using Te and TeO2 provided uniform and any desired composition. The properties of the film depended on the x value; increasing x to as large as x=1.2, which represents a Te‐poor composition, produced an excellent humidity and heat stability, and decreasing x to 0.8 made the film more sensitive to a laser diode, but susceptible to humidity. The TeO1.1 thin film was found to sufficiently satisfy all requirements for practical disc applications. A reflective optical disc was prepared using the TeO1.1 thin film deposited on a polymethylmethacrylate substrate with grooves for optical tracking. This disc is capable of recording video signals at real time by laser diodes. It showed no reflectivity changes on recorded or unrecorded areas and no sensitivity change to laser light after long term storage in high humidity and temperature.