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Electro Optical Memory With Write Read and Erase Characteristics

IP.com Disclosure Number: IPCOM000077797D
Original Publication Date: 1972-Sep-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Tseng, SC: AUTHOR [+2]

Abstract

In the prior art, it is known that information can be stored in crystals, either by optical damage or by charge trapping at the interface between a crystal and a dielectric layer. One of the serious problems in the prior art is that the information so stored diminishes and finally disappears after a short-life time. This is because the charge pattern generated by optical damage or by trapping at the interface state tends to restore to its original distribution, by internal thermal energy of the crystal lattice.

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Electro Optical Memory With Write Read and Erase Characteristics

In the prior art, it is known that information can be stored in crystals, either by optical damage or by charge trapping at the interface between a crystal and a dielectric layer. One of the serious problems in the prior art is that the information so stored diminishes and finally disappears after a short-life time. This is because the charge pattern generated by optical damage or by trapping at the interface state tends to restore to its original distribution, by internal thermal energy of the crystal lattice.

This description relates to a scheme where the storage of the information is permanent. The scheme is shown in the figure, where substrate 1 is a photoconductive and electro-optical crystal such as Bi (12) SiO (20) or bi(12) Ge O(20). Both layers 2 and 3 are dielectric films. The electron energy bandgaps of the three materials delta E(1), delta E(2), delta E(3) are so chosen that delta E(2) > delta E(3) > delta E(1). Elements 4 and 5 are transparent electrodes.

Information, in image, or hologram form, carried by a light beam generates, in substrate 1, a pattern of electrons similar to the light image. Upon application of an electric voltage pulse between the two transparent electrodes, the electrons will tunnel through a thin-insulator layer 2 and subsequently be trapped between the interface state of layer 2 and layer 3. Even if the electric field is removed, the trapped electrons cannot ret...