VCCS

The Valved Corrosive Material Cracker Source VCCS is designed for controlled injection of radicals of antimony, tellurium, magnesium or other corrosive materials in standard MBE applications. Parts directly exposed to the evaporant like crucible, valve mechanism, injector tube and cracker are solely made from PBN to minimize corrosion of the cell.

A mixture of larger molecules of, for example, Sb_n is produced by sublimation of the evaporant within the reservoir. The resulting beam flux is controlled by an all PBN mechanical valve unit and finally the gaseous molecules are dissociated within the thermal cracker stage to form a molecular beam containing a large ammount of e.g. Sb₂ species.

The source consists of the 420 cm³ reservoir, built into a water-cooled vacuum enclosure that also houses the valve unit, and the injector tube with a thermal cracker unit on top.

Operation of the mechanical valve unit shows fast, stable and reproducible flux control. Together with our valve controller MVCU an easy handling and integration into your MBE system is provided.

Three independent heater circuits allow precise and flexible adjustment of the temperatures in each part of the cell in order to provide sufficient material vapor, avoid condensation within the valve or injector tube and ensure maximum cracking efficiency, each according to the requirements of the particular evaporant. A schematic illustration of the sequence of the different heater stages is shown in the figure on the right.

The special design enables easy and safe refilling of the crucible from the backside of the cell without the need of removing the complete cell from the system.