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Indium Oxide Thin Film Optical Storage Memory

IP.com Disclosure Number: IPCOM000038153D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Brady, MJ: AUTHOR [+2]

Abstract

Erasable and non-erasable data storage at low cost can be accomplished by utilizing thin films of indium oxide and exposure to laser radiation. Laser recording requires relatively low write power and is simple to implement.

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Indium Oxide Thin Film Optical Storage Memory

Erasable and non-erasable data storage at low cost can be accomplished by utilizing thin films of indium oxide and exposure to laser radiation. Laser recording requires relatively low write power and is simple to implement.

Thin films (200 to 2000Ao) of indium oxide (In2O3) can be E-beam evaporated onto substrates such as pyrex, quartz, sapphire, 7740 glass and silicon. The films are deposited at room temperature, are fine grained, and are in the amorphous phase. As deposited, the films have an optical transmission of approximately 20% at 0.5 micron wavelength. The films undergo a phase change from amorphous to crystalline when annealed at approximately 230oC in air, with an increase in optical transmission on the order of 90%.

For read-only storage, amorphous In2O3 films have been exposed to excimer laser radiation at 248 nm (67 mJ/cm2) through a metal mask. Selectively exposed areas undergo a phase transition with attendant modulation of optical density. For a write- read-erase mode, crystalline films are exposed to excimer laser radiation at 193 nm (10 mJ/cm2) for 2 minutes at 10 Hz, also through a metal mask. Areas exposed become darker. When these films are then exposed to 248 nm radiation (67 mJ/cm2), the image disappears, and the film becomes optically transparent again. This process can be repeated with the same results on the same film, with stored memory, as well as unexposed but crystalline films.

A reducti...