A SUPERIOR ENERGY SPECTROMETER CONCEPT
The design
improves the capability of the cylindrical mirror
analyzer (CMA) geometry. While keeping all the advantages
of the CMA, such as unbeatable sensitivity, small size
and integrated electron source, the additional new
features of DESA 100 are large working distance,
uncritical sample positioning and electrically variable
energy resolution. Differential pumping capability and
translation stage make the DESA 100 ideally suited for
in-situ surface monitoring and growth control.
DESCRIPTION
OF THE SPECTROMETER
DESA 100 is a
two stage energy spectrometer. Cylindrical geometry is
chosen to maintain highest possible sensitivity. Both
stages, input lens and energy spectrometer, are derived
from a cylindrical mirror configuration. Unlike a
standard CMA, the focusing is achieved by adjusting the
potential of both the inner and outer cylinder. Further,
the particles enter the cylindrical mirror field in
between the cylinders instead of passing through a slit
into the inner cylinder. The advantage is the large
working distance between spectrometer and sample, as much
as 55 mm, allowing ease of sample positioning in complex
and large systems. The particles are decelerated before
energy selection. Variable resolution is achieved by
adjusting the energy of the particles through the
spectrometer.
HIGHEST
SENSITIVITY
The
cylindrical geometry accepts a very large solid angle
with superior transmission and sensitivity. The large
solid angle is useful for high sensitivity AES and
Scanning Auger Microscopy using a fine focused electron
beam. For Photo Electron Spectroscopy, where the sample
is excited over a larger area, the input lens limits the
analyzed surface to a well defined circular spot.
VARIABLE
ENERGY RESOLUTION
The energy of the particles passing through the
spectrometer can be adjusted and the energy resolution
can be electrically selected over a wide range of values
( 100 meV up to 6 eV). The resolution is computer
controlled and can be independently adjusted for each
acquisition window.
HIGH
ENERGY RESOLUTION CAPABILITY
Setting the
resolving power to values better than 0.05% allows the
DESA 100 to investigate the fine structure of peaks and
to get clues about the chemical state of the surface.
Such high energy resolution can also be performed in
large evaporation systems, offering a unique capability
of in-situ and real time monitoring of the chemical state
of the surface during growth.
UNCRITICAL
SAMPLE POSITIONING
The position of the sample can be shifted over several
millimeters from its nominal position without degradation
of the analysis. The working distance of 55 mm can be
varied by 3 mm without degrading the signal. Both
transmission and energy calibration remain stable. This
unique capability makes the DESA 100 ideally suited for
all surface analysis systems, including large systems
that combine multiple analysis and deposition techniques.
SCANNING
AUGER MICROSCOPY
The superior small spot sensitivity owing to the large
acceptance angle makes the DESA 100 ideally suited for
Scanning Auger Microscopy. Using the MICROFOCUS electron
gun allows a high spatial resolution for Secondary
Electron Microscopy and Scanning Auger Microscopy. The
small size of DESA 100 makes it ideally suited as add-on
component for Scanning Electron Microscopes. |
