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Storage Display by Space Charge Injection

IP.com Disclosure Number: IPCOM000085730D
Original Publication Date: 1976-May-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Hoechli, UT: AUTHOR

Abstract

Optical birefringence is induced spotwise in a surface of a transparent semiconductor sheet by space-charge injection.

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Storage Display by Space Charge Injection

Optical birefringence is induced spotwise in a surface of a transparent semiconductor sheet by space-charge injection.

Write-in occurs by electrical pulses, e.g., by selective application of DC fields with a transverse scanning metal pencil or a matrix-like set of such pencils, respectively. The other surface of the storage sheet is metal coated and electrically grounded. Read-out or observation is done with polarized light.

Wherever the pencil touches the surface, space charge is injected through the storage materials surface which creates an internal polarization in a region around the tip. The material must be highly polarizable but should not possess any permanent polarization. Such is the the case for Ba TiO(3) just above its ferroelectric phase transition temperature. That induced polarization is stored during a time equal to the relaxation time for space charge in the respective material (about half a minute in Ba TiO(3); about a day in Sr TiO(3)).

Polarized light hits the surface region in parallel incidence and is extinguished by the analyzer, if zero information has been written on to the surface along the light path. A bit stored on the surface induces birefringence and thus increases the light intensivity on the screen.

Space-charge writing is insensitive to magnetic perturbations, as arising from large electromagnetic shocks. The device can be shielded, since it uses electrical properties of material only.

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