Thermal sublimation of carbon from high purity graphite filament
Excellent growth of thin carbon films or Si-C alloys
Water-cooled electrical contacts
Inner filament shielding with pure pyrolytic graphite parts
When the Carbon Sublimation Source SUKO was originally developed some twenty years ago, it was a breakthrough for growth of Si-C and Si-Ge-C alloys in silicon MBE. The SUKO still provides a preeminently clean and stable flux at a low deposition rate of up to 2 Å/min. Since then it has also been successfully applied in a variety of other research fields, e.g. graphene formation.
Main parts of the SUKO assembly
At typical operation conditions the SUKO graphite filament is glowing at a temperature of about 2200°C. Especially for heat sensitive substrate materials it should be taken into account that a lot of radiation is impinging on the surface of the substrate during exposure.
The SUKO is most frequently used in III-V MBE and Si MBE for growth of Si1-xCx or Si1-x-yGexCy alloys. When growing atomically thin carbon layers in Si MBE, the maximum growth rate at a distance of 200mm should not exceed 1Å/min.
In general, the electron mobility turns out to be comparable to those achieved by Be doping. Optical, REM and x-ray studies have all confirmed the excellent morphology of the layers.
Due to its outstanding properties, particularly with regard to flux stability and reproducibility, the SUKO today is also applied for a number of other applications, e.g. investigation of graphene, carbon doping in III-V MBE, etc. See DECO-D for details on carbon doping.
In contrast to carbon gas sources no interaction with MBE equipment or any memory effect is observed while operating the SUKO.
Over the operating time the filament naturally becomes thinner, whereby the flux rate at a given current gradually increases. Tthe current should therefore be recalibrated and eventually reduced from time to time to keep the flux rate constant.
The lifetime of a graphite filament strongly depends on the control of the flux rate. This is especially important when operating at flux rates close to the maximum rate of the respective SUKO model. A runaway increase of the flux rate can result in a premature burning out of the filament. Under normal conditions a maximum total carbon layer thickness of 5µm with one filament is reported.
For Carbon Sublimation Sources optimized for doping applications please refer to our specialized source type SUKO-D.
Several publications based on samples grown with SUKO sources are listed in section References / List of Publications.
|Filament type||high purity graphite filament|
|Filament shielding||filament completely shielded with PG parts|
|Thermocouple||W5%Re/W26%Re (type C)|
|Operating temperature||max. filament temperature 2300°C|
|Electrical contacts||water-cooled (4x Swagelok fitting connection O.D. 6mm); water flow min. 30 l/h|
|Cooling||separate water (or LN2) cooling shroud|
|Options||integrated rotary shutter (S)|
|Schematic drawing of the Carbon Sublimation Source SUKO
(drawing shows SUKO 40)
For general information on CF mounting flanges see Flange and Gasket dimensions.
|[mm] / [mm]||[W] / [A]||[Å/min]||Product code|
|SUKO||40 -||LxxxD36||455 / 75||0.5||PS 20-76|
|SUKO||63 -||S -||LxxxD55||950 / 100||2||PS 20-120|
|SUKO||100 -||LxxxD95||5000 / 100||10||PS 60-100|
|*||rotary shutter possible on same flange|
|**||maximum growth rate at 100mm distance|
|***||specify UHV length L with order|
e.g. SUKO 63-S-L300D55
is a carbon sublimation source on DN63 CF-flange with shutter, in-vacuum length 300mm and diameter 55mm.