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Surface, Interface and Nanostructure Research Group |
Research |
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Group Focus |
Discuss our main research interests here | |
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Lab Capabilities |
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First Floor LEED/Auger System
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The first floor LEED (low energy electron diffraction) system was specifically designed for
the purpose of taking samples from air pressure down to a UHV environment
in as little time as possible. To accomplish this, two load lock chambers are
built onto the system. During a typical sample transfer, the first chamber is
vented to air pressure. The sample is then placed in the chamber and pumped
on with a turbo molecular pump. After a few minutes, the chamber can then be
opened to a second chamber. The second chamber acts as a buffer between the first
chamber and the main chamber where the LEED is located. By utilizing a second load
lock, the pressure gradient between load locks is minimized and the amount of
contaminants such as water vapor particles is greatly reduced. The result is a
much shorter pumping time before data can be taken. Once the second chamber is
opened it is taken into the main chamber via transfer arm, where it can be studied
using LEED and Auger techniques.
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Room Temperature STM, LEED/Auger
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This system's main purpose is for scanning tunneling microscopy and
spectroscopy under ultra high vacuum at room temperature. It is equipped
with a custom in-house built STM featuring:
- 2 stages of mechanical vibration isolation via magnetic damping and spring
systems (the entire apparatus is mounted on an 8 inch conflat flange)
- tip motion piezoceramic tube actuators (Staveley Sensors Inc.)
- an in-situ current to voltage converter
- a servo feedback circuit
- a 10 space tip parking lot
- in-house etched tungsten tips (polycrystalline or single crystal.)
In addition to the STM, the chamber is outfitted with a cylindrical mirror
electron energy analyzer (CMA) for Auger electron spectroscopy, a low energy
electron diffraction (LEED) system, a Field Emission/Ion Microscope
(FEM/FIM), Si and Ni rod evaporators and an electron bombardment sample
heater. The system houses a turbomolecular pump backed by a diaphragm pump
(Pfeiffer) and an ion pump with 500 L/sec pumping speed (Perkin Elmer.) A
valved load lock apparatus allows sample and tip transfer without a needing
to break vacuum. The sample manipulator can move in three orthogonal
directions and allows rotation along one axis. Samples are moved around in
situ via two wobble sticks with custom pincers and can be deposited in a
rotatable 8 space sample parking lot. The custom sample holders used are
molybdenum and samples are held in place with Ta strips spot welded to the
holder. This chamber was assembled in 1990 and has been operational (and
improving) ever since!
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Low Temperature STM, LEED/Auger
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The low temperature system has the ability to efficiently swap samples and tips without breaking
Ultra High Vacuum. A furnace has also been included in the chamber allowing us to create graphene from SiC
samples, which are then placed in the stm and are cooled to temperatures ranging from room or liquid
helium temperatures. We are then able to use the systems capabilities to perform test ranging from LEED,
STM, capacitance, dI/DV and BEEM to further understand graphene's physical characteristics. For a more
in-depth view of they systems design please refer to
An ultrahigh vacuum cryogenic scanning tunneling microscope with tip and sample exchange.
Currently Kevin and Lee are busy upgrading the systems transfer system and operating structure, though
throughout this process the Low temperature system is often being used to better the process of bettering
epitaxial methods and is gleams as much information as possible with each passing sweep of its piezos.
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