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|Title: ||A Vertical Coarse Approach Scanning Tunneling Microscope|
|Authors: ||Drevniok, BENEDICT|
Scanning Probe Microscopy
Scanning tunneling microscopy
|Issue Date: ||2009|
|Series/Report no.: ||Canadian theses|
|Abstract: ||A Pan-style scanning tunneling microscope (STM), with a vertical coarse approach
mechanism, was designed, built and tested. The microscope will be operated in
ultra-high vacuum and also at cryogenic temperatures (8 K) inside a continuous
flow cryostat. Fundamental differences in operating principle exist between the new
microscope and the beetle-type inertial sliders  that have been the mainstay of
the group for the last eight years. While Pan-style microscopes do already exist ,
they remain challenging to build, and an active area of research . This system
represents a bold departure from well-trodden paths, and will greatly expand the range of experiments that our group can perform.
The operating principles of inertial piezoelectric motors are detailed. Design guidelines for a piezoelectric motor are given, and used in the design of the vertical coarse
approach motor. A simple, inexpensive implementation for creating waveforms with
an extremely fast fall time is discussed. Motor performance is tested, and a minimum
step size of 20nm is found for frequencies ranging from 0 Hz to 3 kHz. The motor
operates with high dynamic range: individual 20nm steps can be taken, as well as
being able to move at a velocity of 0.4mm s−1.
Little is known about the vibrational properties of Pan-style microscopes. Vibrational testing of the microscope revealed the expected scanner bending mode at 1.6 kHz (above the scanner bending mode of our beetles at 1.2 kHz), and a complicated
response signal above this frequency. Custom extension springs for an eddy-current
damping system are built and tested. A low resonant frequency of 1.8 Hz is found,
which is ideal for the application.
Initial testing of the STM in ambient conditions is performed on two different
surfaces. A moir´e supermesh  with periodicity 3nm is observed on a highly-oriented pyrolytic graphite (HOPG) surface, and agrees well with previously published results.
Using a flame-annealed Gold on mica surface, a low drift rate of 0.6nm s−1 is observed
over a period of 13 minutes. Single-height atomic steps are observed on both surfaces.
Additionally, the microscope is shown to be capable of zooming into different features
on a surface, and scanning at different length scales.|
|Description: ||Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2009-06-24 13:06:16.683|
|Appears in Collections:||Physics, Engineering Physics & Astronomy Graduate Theses|
Queen's Theses & Dissertations
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