MBE Components, Valved Corrosive Material Cracker Source VCCS

VCCS

Valved Corrosive Material Cracker Source

VCCS 100-420 Sb valved corrosive material cracker source on DN100 CF (O.D. 6") mounting flange (with adapter flange VADP 100-63-K)

Evaporation and cracking of Sb, Te, Mg, and other corrosive materials
Large crucible capacity of 420 cm³
All PBN construction of valve and cracker stage
Fast, stable and reproducible flux control
Easy installation and refilling procedure
Injector length and mounting flange adjustable to fit most MBE systems

Data Sheet

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.		Additional equipment for the VCCS (motorized valve control unit MVCU with temperature controllers and power supplies)
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.		Schematic sketch of the VCCS building blocks. The PBN-funnel (2) connects the PBN reservoir (1) with the full-PBN valve (3). The evaporant is guided to the cracking stage (5) by a PBN injector tube (4). For better homogeneity there is a beam shaping funnel (6) on the orifice of the VCCS.

Application

The main purpose of the VCCS in MBE applications is enhanced flux control and cracking of materials whose vapor is highly corrosive to metallic surfaces. The VCCS was originally designed as a source for an antimony radical (Sb₂) molecular beam as group V material in standard III-V MBE. It uses the well-established concept of sublimation of elemental Sb_n followed by a step of thermal dissociation in a cracker stage to produce a Sb₂ molecular beam. The VCCS all PBN construction of the inner parts, in particular the valve mechanism, in combination with the flexibility provided by three independent heater circuits allows applying this concept to other materials like Te, Mg or Se.

The valve mechanism and hence the beam flux can be regulated either manually or remotely by a servo motor drive (MVCU) with a 0-10 V analogue input signal.

A large crucible capacity of 420 cm³, fast and precise flux control and easy handling for maintenance and crucible refill make the VCCS an ideal source for smaller production MBE systems as well as for higher throughput research MBE systems.

References

Several publications based on samples grown with VCCS sources are listed in section References / List of Publications.

Technical data
Filament type	3 separate heater-circuits (cell / valve / cracker)
Thermocouple	3 W5%Re/W26%Re (type C) thermocouples (cell / valve / cracker)
Operating temperature (for Sb-sublimation)	cell crucible: 550-650°C; valve: 600-700°C; cracker: 650-1200°C
Outgassing temperature	cell crucible: 800°C; valve: 900°C; cracker: 1300°C
Bakeout temperature	250°C
Cooling	integrated water cooling shrouds
Crucibles	420 cm³
Flux control	integrated all PBN valve mechanism / cell temperature
Valve control	stepper motor drive with control unit MVCU

Dimensions

Schematic drawing of the Sb-Valved Corrosive Material Cracker Source VCCS

(drawing shows
VCCS 100-420 with VADP adapter)

Specific data

For general information on CF mounting flanges see Flange and Gasket dimensions.


		[cm³]	[mm] / [mm]		[W] / [A]	Product code
VCCS	100* -	420**-	LxxxD38		cell : 315 / 9 valve : 400 / 8 cracker : 455 / 13	cell : PS 60-12.5-C valve : PS 60-12.5-C cracker : PS 40-19-C

*	other mounting flange diameters feasible in combination with VADP adapter flanges (on request)
**	other capacities on request
***	specify UHV length L with order

Product code:

e.g. VCCS 100-420-L305D38

is a valved corrosive material cracker source on DN100 CF flange with 420cm³ crucible and UHV-length 305mm.

Related products

The following list provides suggestions for related products. For additional product suggestions or more detailed information, please contact us.

Components


Valved Thermal Cracker Cell VTCC	Thermal Cracker Cell TCC

Accessories


Motorized Valve Control Unit MVCU	Beam Flux Monitor BFM

Systems


OCTOPLUS 400	OCTOPLUS 600