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Browse Prior Art Database

Write-Once Data Storage using Amorphous Silicon

IP.com Disclosure Number: IPCOM000104283D
Original Publication Date: 1993-Mar-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 1 page(s) / 36K

Publishing Venue

IBM

Related People

Foster, J: AUTHOR [+3]

Abstract

This disclosure describes a technique for storing information as a series of topographic changes made to the surface of a wafer of amorphous silicon. The marks are made by applying a large voltage pulse to the tip of a scanning tunneling microscope (STM) operating in close proximity to the sample surface. The voltage pulse causes an amorphous/crystalline phase change to occur in the material, and creates an associated expansion of the outer layers of the material. Readback is performed by using the STM to scan over the appropriate area, with the tip kept at a fixed distance from the sample surface by the STM servo loop. The signal applied to the Z-motion device (usually a piezo-electric tube) to maintain this spacing is then monitored as the readback signal.

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Write-Once Data Storage using Amorphous Silicon

      This disclosure describes a technique for storing information
as a series of topographic changes made to the surface of a wafer of
amorphous silicon.  The marks are made by applying a large voltage
pulse to the tip of a scanning tunneling microscope (STM) operating
in close proximity to the sample surface.  The voltage pulse causes
an amorphous/crystalline phase change to occur in the material, and
creates an associated expansion of the outer layers of the material.
Readback is performed by using the STM to scan over the appropriate
area, with the tip kept at a fixed distance from the sample surface
by the STM servo loop.  The signal applied to the Z-motion device
(usually a piezo-electric tube) to maintain this spacing is then
monitored as the readback signal.

      The recording medium was a 400A  thick film of
hydrogenated amorphous silicon, deposited on molybdenum-coated glass
substrate.  The silicon film which was heavily doped to provide
adequate electrical conductivity.  The "write data" was a -7V, 200
nsec pulse train applied to the STM tip, resulting in "bits" of
roughly 1600A  breadth and 850A  high established
on the silicon surface.  The raised areas ha slightly higher
electrical conductivity than the surrounding film, indicating that
they were at least partially crystallized.  Readback of the bit was
performed as described above, by monitoring the trajectory of the tip
in the z-direction. ...