RHEED screens are mainly used within MBE and PLD deposition systems where single crystalline layers are prepared. From RHEED oscillations the growth rate can be precisely determined as well as lattice mismatches in heteroepitaxial systems.
RHEED screens are used to display RHEED patterns (see picture on the right hand side) obtained from the diffraction process initiated by electrons hitting a single crystalline substrate under crazing angle with high kinetic energy. Fluorescence effects in a thin phosphorus layer make each diffracted beam visible as a spot on the screen. By using a video camera system the RHEED data can be recorded and evaluated (with the SAFIRE software) accordingly. Depending on the material system used in the preparation chamber, indium-tin oxide (ITO) or aluminium (Al) coated screens are used. A standard RHEED screen configuration is based on a RHEED screen (phosphorus coated lead glass disk), a RHEED screen holder (for mounting) and a standard UHV window. Optionally, a shutter is available to protect the RHEED screen in case of using aggressive gases during the deposition process. The screens are available in sizes fitting to 6" or 8" CF flanges and they can be easily clamped by special RHEED screen holders designed for fast and easy mounting and exchange. Good electrical conductivity is achieved by either an indium-tin oxide (ITO) or an aluminium (Al) coating which in addition suppresses stray light from inside the chamber. The viewing screen utilizes a short persistence (P43) zinc sulfide (Cu activated) phosphor coating on a lead glass (for absorption of X-rays).