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Introduction |
Specifications |
Description |
XPEEM and LEEM methods
Operating principle
A LEEM-PEEM microscope images a specimen that is illuminated with soft x-rays, ultra-violet (UV) radiation or low energy electrons. The emitted photoelectrons, or the elastically reflected electrons, are accelerated by a strong field in the objective lens, of which the specimen is an integral part. The objective produces a magnified image of the specimen, which is further magnified by several additional lenses in the imaging column of the instrument. The image
is finally projected onto an imaging MCP detector with phosphorous screen. This is imaged in real-time by a computer controlled CCD camera.
Operation modes
Imaging. The sample is illuminated with x-rays or UV radiation, to excite photoemission, or with electrons. IL and P1 image the specimen image produced by the objective. The specimen image is finally projected onto the detector by the action of P2 and P3. The contrast aperture in the diffraction plane limits the angular acceptance for optimum resolution.
SPELEEM operation: XPEEM & LEEM imaging mode
Micro-diffraction. A coherent beam of electrons is used to illuminate a crystalline surface, thus producing a LEED pattern. IL and P1 image the diffraction pattern produced in the backfocal plane of the objective lens. Inserting the analyzer exit slit allows angle resolved photoemission and x-ray photo-electron diffraction measurements. The probed area is selected by inserting the field-limiting aperture in the image plane after the objective lens.
SPELEEM operation: micro-diffraction mode
References
SPELEEM: combining LEEM and spectroscopic imaging;
Th. Schmidt, S. Heun, J. Slezak, J. Diaz, K. C. Prince, G. Lilienkamp, and E. Bauer;
Surf. Rev. Lett. 5 (1998) 1287-1296.
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