- How
long does a probe last?
AFM probes can be used until the tip becomes broken or contaminated.
The probes can be broken if they hit the surface unexpectedly during
probe approach or if the scan rate is too high during image acquisition.
Probes can become contaminated if the sample surface that is being scanned
has too much contamination on it.
- Does
the probe touch the surface in an AFM?
This depends on your definition of "touch". For the AFM to
image a surface, the probe must come within the "force field"
associated with the surface. Long range forces in ambient air are associated
with a contamination layer and close range force are associated with
mechanically touching the surface. The forces between the end of the
probe and the surface can be as small as a few picoNewtons.
- What
is the difference between vibrating mode (tapping, non-contact, close
contact and contact probes)?
Cantilevers that are used for vibrating modes (tapping, non-contact,
close contact) are typically much smaller than the cantilevers used
to contact mode. Thus, the resonance frequency of vibrating mode probes
is much greater than that of the contact mode probes.
- Does
Probestore make their own probes?
Probestore.com is the distributor for NanoWorld which is based in Switzerland.
NanoWorld is the largest manufacturer of AFM probes in the world. NanoWorld
purchased the rights to manufacture probes offered by NanoSensors.
- What
is the probestore's policy for returns?
All sales of probes are final. However, if there appears to be a quality
issue with probes purchased from Probestore.com, then the Probestore
adheres to the return policy of NanoWorld.
- What
are the advantages of Silicon Nitride probes?
Silicon Nitride cantilevers typically have a triangular (or pyramidal)
shape. There are no advantages of Silicon Nitride probes over Silicon
probes for contact scanning. Typically, silicon tips are sharper than
silicon nitride tips.
- What
is the crystallographic orientation along the cantilever axis in Si
probes?
The cantilever is aligned parallel to the <110> direction.
- Which
parameters are precisely known for the determination of the resonance
frequency and the force constant?
The cantilevers are made from monocrystalline silicon, therefore resonance
frequency and the force constant are very precisely determined by the
geometry of the cantilever requiring no calibration. The thickness of
the cantilever is measured with an optical microscope. Resonance frequency
and force constant are calculated with these measured values taking
the approximate mass of the tip into account. The measurement errors
and the simplification used in the calculation lead to the following
error values for the resonance frequency and the force constant: Approximately
10% error for cantilevers 450 µm in length; Approximately 20%
error for cantilevers 125 µm or 225 µm in length.
- What
exactly is meant by "mean width" concerning the geometric
dimensions of the cantilever?
The cross section of the cantilever is trapezoidal. Therefore, the cantilever
has two geometrical widths, a smaller one on the tipside and a broader
one on the opposite side. Thus, "mean width" describes the
median between those two values. E.G. the width on the tipside may be
20 um and the width on the opposite side may be 40 um resulting in a
"mean width" of: (30 µm + 40 µm)/2=35 µm.
- Does
the tip radius of the SuperSharpSilicon™ tips increase over a long
period of time due to secondary oxidation?
Control measurements after six months of storage time have shown no
change in the tip radius. The tip radius was still found to be 2nm or
better.
- What
is the difference between mounted and unmounted probes?
Mounted probes are supplied with the probe chip attached to a metal
substrate. Mounted probes are easier to handle and thus are easier to
use. Unmounted probes are less expensive but are more difficult to use.
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