VCCS Effusion Cell  | © Scienta Omicron
VCCS. Source: MBE-K.

Valved Corrosive Cracker Source (VCCS)

Controlled Injection of Radicals of Sb, Te, Mg or other Corrosive Materials

PVDMBE

  • Evaporation and cracking of Sb, Te, Mg and other corrosive materials
  • Large crucible capacity of 420 cm³
  • Fast, stable and reproducible flux control
  • All PBN construction of valve and cracker stage
  • Easy installation and refilling procedure

The Valved Corrosive 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 the crucible, the valve mechanism, the injector tube and the cracker are solely made from PBN in order to minimise corrosion of the cell.

A mixture of larger molecules 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 well-defined molecular beam, e.g. of 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 the valve controller an easy handling and integration into the 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 vapour and avoid condensation within the valve or injector tube. They also ensure maximum cracking efficiency, each according to the requirements of the particular evaporant.

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.

Further Details:

  • DN100CF (6” OD) mounting flange (or DN 63CF (4.5” OD with VADP adapter flange)
  • Crucible 420 cm³
  • Heating system with three separate heater-circuits for the cell, the valve and the cracker
  • Three thermocouples Type C for the cell, the valve and the cracker
  • Operating temperature of the cell crucible: 500-550°C
  • Operating temperature of the valve: 600-650 °C
  • Operating temperature of the cracker: 900-1000 °C
  • Outgassing temperature of the cell crucible: 900 °C
  • Outgassing temperature of the valve: 1000 °C
  • Outgassing temperature of the cracker: 1300 °C
  • Integrated water cooling shroud
  • Bakeout temperature up to 250 °C
  • Flux control with integrated all PBN valve unit
  • Valve control either via hand control or by a motor drive with a control unit