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As part of a "Wright Center for
Innovation," SCSAM has acquired a
state-of-the-art multi-mode scanning probe
microscope (SPM), a Dimension 3100 (Veeco
Digital Instruments), equipped with a
NanoScope IIIa controller and Quadrex
signal processor for 16-bit resolution on
all 3 axes. The tool works under
atmospheric pressure at room temperature
and can work in air and in liquids, so that
a full range of materials (metals,
insulators, ceramics, polymers, and
biological specimens) can be investigated
with minimal sample preparation. It can
accept samples up to 20 cm in diameter,
with a height limitation of < 1.5 cm and
a surface roughness limitation of < 5.5
mm. The SPM is equipped with an in-line
optical zoom microscope with color CCD
camera, with a maximum magnification of
800X for precise placement of the SPM probe
onto the sample.
The SPM can operate in numerous imaging
modes, the primary operation being atomic
force microscopy (AFM) in contact mode,
tapping mode, and phase imaging mode. Other
data collection techniques include
conductive-AFM to characterize conductivity
variations; magnetic force microscopy,
which uses a ferromagnetic-coated tip to
probe magnetic fields; and force-distance
measurements, which are performed to study
attractive and repulsive forces on a tip as
it approaches and retracts from the sample
surface.
By exploiting all of these capabilities,
the SPM is a versatile tool for
characterizing materials properties and
surfaces. Measurements include surface
roughness, step height, and particle size,
with a noise floor in height measurement of
0.02 nm. Also, fundamental force
interactions can be investigated, such as
nano-scale adhesive and elastic response,
binding forces, colloidal studies, and
chemical sensing.
The SPM system is equipped with
comprehensive image analysis software. Full
2D and 3D mapping and displays can be
generated, with a variety of slope and
flatness corrections. Ra and rms roughness
calculations can be done on selected areas,
as well as a multitude of additional
statistical calculations. Image files can
be exported in tif, ascii, and jpg
formats.
The Dimension 3100 SPM has been upgraded
by a "TriboScope," an attachment for
nanomechanical testing, made by Hysitron.
The TriboScope is a quantitative,
depth-sensing nanoindentation and
nanoscratch system that interfaces with the
SPM. This attachment enables quantitative
characterization of mechanical properties
(hardness, scratch resistance, wear
resistance) on the nanometer length scale
and in situ AFM imaging of the surface
topography before and after mechanical
testing. The capability of in situ imaging
allows the user to choose the exact area,
with sub-nm precision, for each
nanoindentation/nanoscratch investigation,
and to fully characterize the local
specimen surface. Thus, the user can
minimize the effects of random surface
roughness, can investigate specific
features or phases, and can place indents
within nanometers of interfaces. This is
particularly useful for profiling
cross-sectional specimens. Post-mechanical
testing imaging also provides information
on fracture toughness, adhesion, and
interface strength, among other
properties.
The Triboscope comes with data analysis
software that provides hardness, reduced
modulus, and specimen stiffness, in
addition to the raw load-depth data. The
tool operates in load control with a
maximum load is 9500 mN. The loading and
unloading rates are fully
operator-controlled, allowing additional
investigations, such as creep rate,
anelasticity, and loading-rate effects.
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