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The PHI VersaProbe XPS Microprobe is a
multi-technique surface analysis instrument
based on PHI's highly developed scanning
X-ray microprobe technology. The most
important advantage of this instrument is
that the VersaProbe can produce a
focused, highly monochromatic
X-ray beam that can be scanned
over the specimen surface. In this
instrument, a point source of X-rays is
created by focusing an electron beam onto
an Al anode. A monochromator, consisting of
an ellipsoid-shaped crystal, collects
X-rays from the point source and focuses
them on the surface of the specimen. The
focused X-ray beam can be scanned across
the specimen surface by correspondingly
scanning the electron beam across the
surface of aluminum anode. A major
advantage of this design is that most of
the photoelectrons generated by the focused
X-ray beam are actually collected by the
electron energy analyzer, whereas in the
conventional design, most of the
photoelectrons are lost. With the
VersaProbe, the spot size can be varied
between less than 10 μ diameter
(for highest spatial resolution) to
100 μ (for highest sensitivity).
The field of view can be as large as
1500 μ by 1500 μ. In
addition to the X-ray beam focusing and
scanning ability, the VersaProbe also
significantly improves the Center's
previous instrument with the following
features:
- A 180 ° hemispherical
electron energy analyzer optimized for
energy resolution and PHI's high angular
acceptance lens optimized for small area
XPS sensitivity.
- A UHV analysis chamber with multiple
ports aligned to the sample analysis
position allowing multi-technique
configurations.
- A unique, 16-channel detector and
fast electronics for rapid data
acquisition and maximum sensitivity in
both the scanned and unscanned data
acquisition modes.
- A new, dual-gun charge compensation
system for the analysis of
insulators.
- A fully automated, five-axis (x,
y, z, rotation, and tilt), precision,
eucentric specimen stage that uses the
computer to locate selected analysis
positions. Stage motion allows access to
all points on the specimen surface.
- Large specimens – diameter
up to 60 mm.
- A 100 V to 5 kV
differentially pumped Ar ion gun with
regulated leak valve for specimen
cleaning and depth profiling.
- A microscope, camera, and a light
source for sample positioning.
- A computer system with a modern
operating system, controlling all
necessary hardware, analysis, data
processing, and data output.
- Software for surveys, high-resolution
multiplexes, sputter depth profiles, line
scans, chemical images, automated
analyses, and user-defined settings.
Provides full support for
automation.
- Software with an extensive library of
post-analysis data processing algorithms
(background subtraction, smoothing, peak
identification, linear least squares
fitting, target factor analysis, curve
and peak analysis and separation of
multiple chemical states in maps, line
scans, profiles).
Based on these advanced features, the
VersaProbe provides the following
techniques that conventional XPS systems
either cannot perform or can only perform
with much inferior results:
- High performance micro-area
spectroscopy.
- High sensitivity large-area
spectroscopy.
- Chemical state imaging.
- Angle-dependent spectroscopy.
- X-ray-induced secondary electron
imaging.
- High-performance sputter
depth-profiling.
- Hands-off charge neutralization.
This material is based upon
work supported by the National Science
Foundation under Grant
No. MRI-0722920. Any opinions,
findings, and conclusions or
recommendations expressed in this material
are those of the author(s) and do not
necessarily reflect the views of the
National Science Foundation.
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