Eduard Hartung and Sven Engbers

Cathode ray – light sources

Applications● Electron microscopy● Cathode ray tube ● oscilloscope● Electron beam lithography● X – ray tube● ...

History

● 1897: Karl Ferdinand Braun – Inventor of the Braun tube

● 1906: Max Diekmann – First electrical TV (3 x 3 cm, 10 fps)

● 1926: Kenjiro Takayanagi– First black – and – white picture tube in Japan

● 20. century: Professor Manfred von Ardenne – Constant further development

Cathode ray tube - construction● Cathode● Wehnelt cylinder

– Brightness control, contrast optimisation

– Pre focussing● several focussing electrodes● Deflection plates / coils● Anode

– Acceleration

Cathode ray tube – Ray generation

● Heating of the cathode● Electron cloud between cathode and Wehnelt cylinder● Acceleration due to high electric field

– Oscilloscope: 500 – 8000 V– TV: 25 – 35 kV– Material processing / X – ray tubes: >100 kV

● Current <1mA

Cathode ray tube – beam deflection and modulation

● TV's:– Magnetic deflection

(Coils)● Oscilloscopes:

– Electrostatic deflection (Pair of plates)

● Modulator electrode (Wehnelt Zylinder)

– Negative electrical potential compared to cathode

– Modulation in the range of MHz

– Amplitude about 250 V

Cathode ray tube – Color● Three electron guns (red,

green, blue)● aperture grille design

– High brightness● Shadow mask design● Chromaclear design

Scanning electron microscope

● Resolution of ~2nm● High depth of sharpness● Information about

compounding of

Fundamental building

Electron-gun

Thermionic Gun Field-emission gun

Fokusing Lens

Magnetic electron-lens Fokusing with lorenz-force:F=e⋅×B

Reaktion in Material

● Secondary electrons● Back scattered elctrons● x-Ray

Detektion

Everhart-Thornlay detector

Thank you for your attention!

Sources● http://www.uni-tuebingen.de/iap/fprakt/pdf/AnleitungREM.pdf ● http://en.wikipedia.org● Einführung zum Rasterelektronenmikroskop● Skript of Prof. Dr. Lödding