Omicron LT UHV STM Do’s and Don’ts

Omicron LT UHV STM
Do’s and Don’ts
General (Instrument)
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Eye protection should be worn when near to a viewport,
even if using protective covers.
Never touch any UHV surfaces with bare hands. Always
use clean polythene gloves and degreased tools.
Don’t touch table when it’s floating on air legs.
Always be aware of which panel you’re dealing with
(STM vs. Prep Chamber).
Avoid burst valve on STM chamber.
Remember that sample transfers have greatest potential
for disaster.
Never forget to update contents of carousel
Never turn on ion pumps or gauges when pressure is
<1x10 -6 mbar
Never stand on compressed air lines or let them get
loose.
General Instrument continued
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Do not vent the chambers with ion pumps, ion gauges or
STM on.
Never flash the TSP with a clean sample in the chamber.
Turn the TSP off on the control panel after it turns off in
the chamber.
Never turn off the sample heather without turning the dials
on the panel all the way to zero.
Never put large forces on the position handle on top of the
STM.
Never use the tunneling position, where STM is hanging
freely, when moving the STM, operating the wobblestick,
or during bakeout.
Do not forget to take the cap off of the Helium cylinder
before it’s returned to the Airgas company.
General (Nuts & Bolts)
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Do not use tools made from Ni-alloys when
handling silicon samples. Steel and stainless
steel contain sufficient amounts of nickel to
contaminate the sample. Omicron recommends
using molybdenum or ceramic tools.
Never use a stainless steel sample plate at high
temperatures, such as during degassing, in order
to avoid nickel contamination in the UHV system.
Use a tantalum sample plate.
Use only the originally supplied molybdenum
wrench for tightening the molybdenum nuts.
The sample holders are delicate – use care when
changing sample
General (Matrix)
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Do not press buttons while the matrix loads.
Avoid excessive button-pressing after matrix has
loaded.
Be sure to load the experiment, change the
Raster setting to Single Point, and choose the
correct temperature settings after loading matrix.
When a line scan is unresponsive, close it out
and open another by duplicating the topology
screen.
Use the coarse movement remote box to move
the scanner close to the sample, but use the
auto-approach option in matrix when
approaching.
Wobblestick
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The wobblestick can be moved to and fro, up and down and
sideways, but should never be rotated.
Avoid damage to bellows as to prevent vacuum leaks:
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Do not scratch the wobblestick bellows at parts of the cryostat,
carousel or chamber.
Do not bend the wobblestick too heavily to avoid deformations to
the sleeve. If movements prove difficult try gently wobbling the
wobblestick.
Always use small angle wobblestick movements.
Never use wobblestick without fully retracting tip, or there is
a danger of snapping off the scan tube.
Never use wobble stick if STM stage isn’t locked in cold
position.
During a transfer, do not move the wobblestick up and down,
as it will damage the sample holder clips.
Always be sure that the wobblestick is secure after use, by
wobbling it back and forth.
Stay away from wobblestick when not in use.
Bakeout
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Maximum bakeout temperature: 150°C.
Bring the LT STM to its bakeout position before
starting a bakeout procedure or the suspension
springs may extend and cause major problems to
the eddy current damping system. Never bake in
the cool-down position or the STM stage may
stick to the chamber.
Never leave a sample plate in the STM during a
bakeout, because the clips could be damaged.
Never use the Si diode for bakeout temperature
control (considering the weak thermal coupling
between SPM head and system during bakeout).
Bakeout continued
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Figure 28 (from
manual) FT 12
connectors
In order to avoid charge build up
during bakeout due to the
pyroelectric effect fit all FT12/19
feedthroughs with their short
circuit plugs.
Remove all non-bakeable parts
from the system (including the
LHe cryostat fast coupling port
and LHe probe) and check the
table for loose plastic. Shield all
viewports with aluminium foil.
Never bake with the magnets on
the sputter gun or the transfer arm
in the load lock.
Cool Down
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The sample stage must stay locked in the cool-down
position with the STM firmly against the cryostat to ensure
maximum thermal contact for cool-down process. The
scanner should not be operated at temperatures above
50°C, because it may lead to a depolarization.
Do not let N2 vents get blocked or clogged with ice.
Never leave liquid Helium cylinder with all vents shut
(apart from transfer itself).
Do not bend the LHe probe. The thin superconducting
wire and stainless steel support tube are very fragile.
Never scan > 200 nm when at 4 K.
Never scan > 300 nm when at 77 K.
The vacuum must be in the lower 10-10 mbar regime to
avoid residual gas particles adsorbing upon the cold
sample surface. The surface sticking probability is close
to 1 for temperatures of 10 K and below.
Setup
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The allowed tip length is limited. The tip must not stick out
more than 2 mm above the tip holder tube.
During loading of sample and tip holder, make sure the
scanner is fully retracted and at its lowest position, and
lock stage.
When transferring a sample, do not use up or down
movements with the wobblestick, and check that the
sample plate is rigidly clamped when fully inserted.
Avoid running the coarse motors on the spot, e.g. at their
limits, for longer periods of time.
When changing temperatures with the tip in tunneling
distance there is an increased danger of tip crash.
Constantly observe the Z-position and be prepared to
retract the tip with the coarse motion drive.
Setup Electronics
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Switch off all units, disconnect mains and wait for
a few minutes (for discharge of the power
supplies) before connecting or disconnecting any
cables.
Never connect or disconnect the preamplifier
supply voltage with the MATRIX CU switched on.
Never have the LT STM connected to the
electronics in the corona pressure region, i.e.
between 10+1 to 10-3 mbar so as to avoid
damage due to corona discharge.
Data Management
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When scanning:
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To save space, attempt to not save bad images –
pressing start and stop for the experiment seems to
work well.
Make a note in the notebook for every image that is
saved, including the scan cycle number. It saves time
when the Image Metrology Explorer is not opened.
Instead open files through
D:drive/OmicronNanotechnology/Matrix/default/Results
Images are saved with the following file names:
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User_date-time_project-experiment_count.mtrx where
the user is default, the project-experiment is STMSTM _Spectroscopy, and the count is the run
number_scan cycle. Each time start and stop is
pushed (a new experiment is started), the run number
increases by one.
Data Management cont.
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Each scan cycle is saved (up/forward,
up/backward, down/forward, down/backward) and
when one of those images is deleted, the others
could be corrupted.
Rather than deleting, files will be moved to
different folders on a biweekly or monthly basis,
sorted by date. It seems however, that images
need to be moved back to the Results folder in
order to be opened correctly in SPIP. (Upon
opening a file with the Heuristic File Importer, the
parameters of the image are guessed, and if we
know the parameters, the image should open
correctly.)
Files currently can not be opened with WSxM
program.