Browse Prior Art Database

Multilayer Memory Elements for Beam Addressable Memories

IP.com Disclosure Number: IPCOM000074105D
Original Publication Date: 1971-Mar-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 3 page(s) / 35K

Publishing Venue

IBM

Related People

Brodsky, MH: AUTHOR

Abstract

This apparatus is a beam writable and read-only memory structure consisting of a metal layer such as gold and an amorphous semiconductor layer such as amorphous silicon which, upon local heating by an electron or optical beam, changes its optical characteristics from a previously heated state. By visual inspection, an unheated two-layer structure of gold and amorphous silicon looks gold-colored when viewed from the gold side. After heating, the two layers form a mixture of gold, crystalline silicon, and amorphous silicon which appears as a matted or silvery colored region and as if a distinct gold layer were no longer present.

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Multilayer Memory Elements for Beam Addressable Memories

This apparatus is a beam writable and read-only memory structure consisting of a metal layer such as gold and an amorphous semiconductor layer such as amorphous silicon which, upon local heating by an electron or optical beam, changes its optical characteristics from a previously heated state. By visual inspection, an unheated two-layer structure of gold and amorphous silicon looks gold-colored when viewed from the gold side. After heating, the two layers form a mixture of gold, crystalline silicon, and amorphous silicon which appears as a matted or silvery colored region and as if a distinct gold layer were no longer present. Other metals are expected to combine with amorphous silicon upon heating; the amount of heat, duration of heating, and temperature are expected to vary depending upon the particular metal chosen, the layer thicknesses, and the purity and preparation condition of the amorphous silicon. Amorphous germanium in contact with metals is also known to crystallize when heated and should act in a manner similar to metals in contact with amorphous silicon layers. Other amorphous materials in the same class of tetrahedrally based semiconductors such as silicon carbide, gallium phosphide and gallium arsenide should also exhibit similar effects with metals. The choice of materials depends on pre and postheating optical properties, required temperatures, total heat, and heating time for each combination.

In A, a light beam, I(0), the reading beam, is incident on two layers 1 and 2 of memory structure 3, where 1 is the metal and 2 is the amorphous semiconductor, and shows reflectance I(R) and transmittance I(T) characteristics of the two- layered structure 3.

After heating locally, a portion 4 of the structure 3 has different optical properties which are determined by the mixture of 1 and 2 and, in general, the reflectance I(R), and transmittance I(T), of the light beam incident on portion 4 are different than before heating. Heating, that is, writing, may be a...