Browse Prior Art Database

Storage Device Using Ferroelectric Films and a Scannable Tip

IP.com Disclosure Number: IPCOM000040249D
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

McClelland, GM: AUTHOR

Abstract

This article describes a direct-access storage device (DASD) and method using scanning tunneling microscopy (STM) technology. To write binary indicia, the localized electric field from a sharp scannable conductive tip is used to polarize a ferroelectric film in either of two directions. To read the indicia, the tip is scanned just over the surface of the dielectric, and the image charge brought to the tip surface is measured. As illustrated, tip 1 is spaced about 50 nm from a ferroelectric film 2 which is about 50 nm thick and supported on a conductive substrate 3. Tip 1 constitutes a read-write head. To write binary indicia, voltage driver 4 brings tip 1 positive or negative with respect to conductive substrate 3, thereby writing a "1" or "0".

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Storage Device Using Ferroelectric Films and a Scannable Tip

This article describes a direct-access storage device (DASD) and method using scanning tunneling microscopy (STM) technology. To write binary indicia, the localized electric field from a sharp scannable conductive tip is used to polarize a ferroelectric film in either of two directions. To read the indicia, the tip is scanned just over the surface of the dielectric, and the image charge brought to the tip surface is measured. As illustrated, tip 1 is spaced about 50 nm from a ferroelectric film 2 which is about 50 nm thick and supported on a conductive substrate 3. Tip 1 constitutes a read-write head. To write binary indicia, voltage driver 4 brings tip 1 positive or negative with respect to conductive substrate 3, thereby writing a "1" or "0". To read, current amplifier 5 is used which maintains the tip at the base plate potential. The charge density brought to the tip by the polarized ferroelectric will be approximately the saturation polarization of the ferroelectric, typically 2.5 X 10-5 coulomb/cm2, which gives 3,000 electrons on a 50 nm wide tip. Since current amplifiers with a RMS noise level of 80 electrons are available, this read signal should be readily measurable. Since this method relies only on the application of a local electric field, it is essential that tip 1 be sharp. If stray charge eventually makes its way to the surface of film 2 to neutralize the effective surface charge due to polarization, reading can be accomplished by applying a low voltage to tip 1 during the read process, so that the shape of the ferroelectric hysteresis...