Valved Cracker Cell: 

Please contact us to find the best suitable model for your needs: webrequest@episerve.de
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# Well suited for As, P, Se & S
# Reduces As / P consumption
# Improved efficiency due to rapid flux response:
As or P beam can be supplied / cut off quickly
# Lower background pressure in the MBE chamber
# Reduction of oxygen background as the source material can support higher temperature than in a standard cell without excessive material loss
# Improved precision, reproducibility & ease of flux control due to precise micrometer valve
# The potential to use either As4 or As2 on demand
# A large useful capacity (up to 2.5 kg of As
6 kg for the production model)
# Reduced contamination

 

Valved Cracker Cells for Te or As

Solid source cracker cells are used to decompose evaporated polyatomic molecules into simpler species. This is achieved using a two-stage source, with each stage having different thermal characteristics. The first stage is simply a large capacity thermal effusion solid source. The flux produced by this stage passes into the second stage, which consists of a tubular cracking zone, which is maintained at a higher temperature so as to pyrolyze the evaporated species and, thereby, eradicate and untracked source molecules.
Solid material crackers are used primarily with elements which sublime as polyatomic species i.e. As, P, Sb, Se, S & Te.
In this kind of cell a valve is used to isolate the source charge from the growth chamber.
Valved Cracker Cells present the best alternative to standard effusion cells for elements which evaporate readily such as those in Group V.

An increase of 5° of the P white condenser corresponds to an increase of P2 flux (at a given setting of the valve) of about 75%

Valved Cracker Cell for Phosphorus

* prevents evaporation of solid P in the chamber during bakeout (Red P has a vapor pressure of 4 x 10-2 torr at 200°C).
* avoids the formation of white phosphorus in the MBE system since P2 condenses preferably on cold parts in the safer Pred form.
* allows opening of the Pred reservoir for reloading without system venting.
* improves the P beam purity because the source can be baked at high temperature before use and isolated from atmospheric pollution when the system is vented.
* easy P2 flux control: reproducibility and stability over several hours are better than 1%
* no flux burst on opening of the valve.
* high vapor pressure P charge outside the MBE system (no bakeout problems).
* compatibility with Ion/Ti sublimation pumping.
* 350 cc Pred capacity .
* large cracker and valve conductances for large BEP at low condenser temperature
* low condenser temperature to avoid Pwhite instabilities.

 

Power supplies and PID temperature controller

Specifications

* Suitable for most cells on the market, including large capacity and high temperature ones.
* Adjustable limiting current using front panel potentiometer
* PID Temperature Controller: Eurotherm 2604 type (900 series as an option), easy to use controller, providing high efficiency regulation and high flux stability.
* 19” rack mountable, deep 450 mm (18”), height see table
* Manual control of the shutter from front panel of CPC or from a computer via the RS-232 interface.
* Each unit is delivered with cables bakeable to 200°C; standard length is 7 m (others lengths available on request).
* System or ADDON connectors, upon request.
* Optional RS232 or RS422 communication for fully automated operation from host computer.
* 7 m bakeable power and TC cables

ADDON effusion cells are designed to use existing customer control electronics wherever possible. When a new one is needed, ADDON proposes a variety of power supplies with modular PIDregulators. They are designed according to the many different cells proposed by ADDON.

Selection of power supply and PID temperature controller

* Single Zone Filament cells require one channel PID/Power unit 1-2604-1.1K
* Double Zone cells, Craker sources require two channels PID/Power unit 2-2604-1.1K
* PID and Power Unit Ordering Information
* Cables included included: Each channel is provided with a 7 m power cable and a 7m thermocouple compensated cable per PID channel.
* PID Controller: Eurotherm Model 2604 controller as standard, others series are available on request.
* Thermocouple: PID controller may be configured for TC type C, K or D.
* Other products:
Sources such as Carbon doping source or H cracker source require specific high current power supplies.