Zeiss GeminiSEM Series Instruction Manual

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3 Product and Functional Description | 3.2 Main Components ZEISS3.2.3 Electron Optical Column | Gemini 1Purpose The Gemini 1 column is the part of the microscope, where electrons are emitted, accelerated, de-flected, focused, and scanned. Main characteristics of the Gemini optics are the beam boosterand an objective lens that consists of a combined electrostatic/electromagnetic lens doublet.USup UExtUEHTUB124973586Fig. 14: Schematics of the electron optics1 GunGenerates the electron beam.2 ExtractorPositive electrode that extracts elec-trons from the filament.3 Anode aperture 4 CondenserCollects and focuses the electron beamonto the specimen.5 Multihole aperture 6 Upper detector: EsB detector or InLensSE Singlet detectorLower detector: InLens SE detector7 Objective lensFocuses the electron beam on to thespecimen surface.8 Scanning coilsDeflect the beam across the specimensurface in what is usually referred to asa raster scan.9 SpecimenUSup Suppressor voltage UExt Extractor voltageUEHT Acceleration voltage UB Liner tube voltageGun A Schottky field emitter serves as gun1 . The filament is heated by applying the filament cur-rent. Electrons are emitted from the heated filament while an electrical field, called extractor volt-age (UExt), is applied. To suppress unwanted thermionic emission from the shank of the Schottkyfield emitter, a suppressor voltage (USup) is applied as well.EHT The emitted electrons are accelerated by the acceleration voltage (UEHT). The beam booster (UB,booster voltage), which is always at a high potential if the acceleration voltage is 20 kV or less, isintegrated directly after the anode. This guarantees that the energy of the electrons in the entirebeam path is always much higher than the set acceleration voltage. This considerably reduces thesensitivity of the electron beam to magnetic stray fields and minimizes the beam broadening.34 Instruction Manual ZEISS GeminiSEM series | en-US | Rev. 2 | 349500-8138-000