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Browse Prior Art Database

Electrostatic Information Storage Using a Force Microscope

IP.com Disclosure Number: IPCOM000100451D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 81K

Publishing Venue

IBM

Related People

Hadziioannou, G: AUTHOR [+4]

Abstract

Disclosed is the use of a force microscope to both write and image electrostatic charge on an insulating surface. Both positive and negative charge regions can be written and the sign of the charge can be determined from the microscope image.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Electrostatic Information Storage Using a Force Microscope

       Disclosed is the use of a force microscope to both write
and image electrostatic charge on an insulating surface.  Both
positive and negative charge regions can be written and the sign of
the charge can be determined from the microscope image.

      A force microscope consists of a lever and tip assembly which
scans over a surface and a sensor which measures the lever
deflection.  For example, the lever can be an electrochemically
etched wire bent near its end and the sensor an optical fiber based
interferometer (1).  The lever can also be oscillated near its
resonant frequency and shifts in this frequence, due to changes in
the force gradient, are detected with the sensor.  A feedback circuit
can be used to maintain the tip at either constant force or constant
force gradient.

      To write charge, a voltage pulse is applied to the tip while it
is just above the surface.  The sign of the deposited charge will be
the same as the sign of the voltage.  The tip is then grounded and
used to read the charge by scanning contours of constant force
gradient.

      If the tip scans over a charge region on the surface, the
charge will cause an increased attractive force between the tip and
sample.  In order to maintain a constant force gradient, the
tip-to-surface distance will increase and a "bump" will occur in the
contour of constant force gradient. The sign of the charge can be
determined by applying a bias voltage between the grounded tip and
electrode on the back of the sample (2).  If this voltage is opposite
in sign from the surface charge, then the tip will feel a reduction
in the attractive force as it scans over the surface charge and the
contour of constant force gradient will become a dip, as shown in the
figure.  Thus, the sign of the charge can be determined.

      Alte...