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Browse Prior Art Database

Passive Feedback System for the Tunneling Microscope

IP.com Disclosure Number: IPCOM000099185D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-14
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

McCord, MA: AUTHOR

Abstract

Disclosed is a method for controlling the vertical position of a scanning tunneling microscope using only electronic components rather than the normal active amplifier.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 65% of the total text.

Passive Feedback System for the Tunneling Microscope

       Disclosed is a method for controlling the vertical
position of a scanning tunneling microscope using only electronic
components rather than the normal active amplifier.

      The scanning tunneling microscope relies on feedback of the
tunneling current between the tip and the to keep the proper distance
between the tip and the  Normally the tunneling current goes to a
current which goes to a high voltage amplifier which a piezoelectric
transducer connected to a tip. if the piezoelectric transducer is
sensitive it can be driven by the circuit shown in the figure.
tunneling current flows through the resistor R.  The developed across
resistor R is then used to directly the transducer, thus eliminating
the need for any  If the tunneling current increases, a larger is
dropped across the resistor.  This voltage is fed the piezoelectric
transducer, which retracts the tip, the current.  The net result is a
stabilization of tunneling current.

      In operation, the sample is brought up to the tip until
tunneling occurs.  Va is then adjusted nominally half the voltage Vt
is dropped across R (or when It = Vt / 2R).  This corresponds to the
point with the highest sensitivity.  The actual voltage (Vt - It x R)
should not change during the course of a scan.  This requires that
the sample be very flat (which is often the or that the piezoelectric
transducer have a very high  The high sensitivity can be o...