Double-Pass DESA 100 Energy Analyzer
DESA 100 Energy Analyzer, 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.