Cryogenic STM
The cryogenic STM is a self-contained module which
may be translated from the top-loading chamber at room temperature into a
UHV insert that extends into the cryostat.
The STM makes electrical contact in the bottom of the UHV insert, where the fixed wiring
is routed through a He exchange gas space. The UHV insert is cooled via the He exchange
gas to avoid vibrations from boiling He.
The STM module contains a 3-axis coarse positioning system
of the tip-sample junction incorporating 18 shear piezo motor stacks.
The sample is mounted on a vertical piezo translator while the tip is mounted on a 2-dimensional,
horizontal translator stage. In addition, the STM module contains an optical system attached to
the 2-dimensional stage that allows the tip-sample junction to be viewed while the STM module is
in the cryostat. The overall STM module was constructed out of a solid piece of
molybdenum to achieve a stiff structural base with
good thermal conductivity. The conical shape of the molybdenum module ensures good thermal
contact when pressed against a
Cu mating cone inside the UHV insert.
With this design, we expect to achieve a temperature of 0.5 degree above the He
exchange gas temperature. The later can be cooled to 2 K with the aid of a "lambda-refrigerator"
inside the cryostat.
Return to the Nanoscale Physics Facility
Online: May 2000
Last Updated: July 2007