Reflection high-energy electron diffraction: Difference between revisions

Revision as of 12:01, 27 September 2012

Revision as of 15:54, 19 February 2013

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===Electron gun===

The electron gun is one of the most important piece of equipment in a RHEED system.<ref name="ichimiya2004"/> The gun limits the resolution and testing limits of the system. Tungsten filaments are the primary electron source for the electron gun of most RHEED systems due to the low work function of tungsten. In the typical setup, the tungsten filament is the cathode and a positively biased anode draws electrons from the tip of the tungsten filament.<ref name="ichimiya2004"/>

The magnitude of the anode bias determines the energy of the incident electrons. The optimal anode bias is dependent upon the type of information desired. At large incident angles, electrons with high energy can penetrate the surface of the sample and degrade the surface sensitivity of the instrument.<ref name="ichimiya2004"/> However, the dimensions of the [[Laue zone]]s are proportional to the inverse square of the electron energy meaning that more information is recorded at the detector at higher incident electron energies.<ref name="ichimiya2004"/> For general surface characterization, the electron gun is operated the range of 10-30 keV.<ref name="braun1999"/>