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АТОМАРНЫЙ ВОДОРОД |
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Specifications |
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Model Number |
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- GaAs, InP, CdTe substrate cleaning
- Promotes 2D epitaxial growth on GaAs by surfactant effect.
- Improves lattice matching in InAs/InP
- Si substrate preparation for GaAs growth
- Generation of atomically flat surface of SiC
- As and P etching
- Selective epitaxial growth in patterned GaAs MBE
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The above curves show the dissociation efficiency of molecular hydrogen cracked on an heated tungsten surface.
The efficiency is strongly dependent of the H2 pressure, that is the flow of molecules for a given source conductance, the flows used here will give system vacuum pressures of 10-6 to 10-5 mbar with the usual pumping speed of standard MBE systems ( pumping speed of several 100 l/min). The best working conditions should take the cracking efficiency / flow rate dependance in consideration.
The following table shows some atomic H flow data at usual working conditions.
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H2 Flux
SCCM |
P system
(400 l/s) |
H/(H2+H)
(2200°C) |
Calculated H
Flux At/s |
| 1 |
4 10-6 mbar |
8,0% |
8,64 10+16 |
| 0,5 |
2 10-6 mbar |
20% |
1,08 10+17 |
| 0,2 |
8 10-6 mbar |
40% |
3,60 10+16 |
| 0,05 |
2 10-6 mbar |
60% |
1,35 10+16 |
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Hydrogen Source
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This source generates a flux of atomic hydrogen through high temperature thermal cracking of molecular hydrogen
(or deuterium) with a tungsten filament. A flux of atomic hydrogen has been shown to convert carbon and oxygen based contaminants on substrate surfaces into volatile species which evaporate readily at relatively low temperatures.
Hence an atomic hydrogen source is very useful for in-situ low temperature cleaning of substrates.
It has also been suggested that growth rate in Ga-rich deposition of GaN is considerably enhanced under a flux
of atomic hydrogen.
An atomic hydrogen source represents an ideal solution for in-situ low temperature surface preparation, substrate cleaning and selective MBE.
The minimum vacuum flange required is a DN35CF (2" / 70mm).
All models are equipped with a water cooling system to regulate the flange temperature .
OPTIONS:
On request, the source can be equipped with a thermocouple which allows regulation of the temperature in the cracking zone.
The thermocouple does not give a readout of the absolute temperature of the filament because it is too high.
It can, however, be used for calibration.
Also as an option the source can be furnished with a second gas entry for use with gases which do not need to be cracked. In this case the W filament can be supplied with 4 Amps so as to avoid condensation in the supply tubes for this gas.
If this source is used in a system without cryopanels (LN2 or water) it is a good idea to install a water cooled panel around the cracking zone. The minimum flange size for this option is DN60CF.
SOME OF THE APPLICATIONS: ( references upon request )
GaAs , InP, InSb, CdTe substrate cleaning.
2D growth promotion on GaAs by surfactant effect.
Silicon substrate preparation for GaAs growth. Generation of an atomically flat surface of SiC.
Selective epitaxial growth in patterned GaAs MBE.
As and P etching.
Lattice matching in InAs/InP.
This source generates a flux of Atomic Hydrogen by high temperature cracking of H2.
SPECIFICATIONS AND MODELS:
| Gas: |
H2 only (For other gases see Gas sources documentation) |
| Cracking efficiency: |
up to 40% |
| Operating cracking temperature: |
from 2000 to 2800 °K |
| Gas connection: |
VCR (0.1 to 1 cc/minute are usual flow rates) |
| CBr4 (option): |
VCR female |
| Thermocouples (option): |
Type C (W Re 5/26) |
MINIMUM MOUNTING FLANGE
Crucible Capacity: |
35CF (70mm OD) |
| Power Supply: |
DC - See attached |
| Mountin flange: |
35CF (2.75") and up |
| In-Vacuum Length: |
according to system |
| Power Supply Connectors: |
System or ADDON |
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MBE
Manufacturer |
MBE
Model Number |
Connecting Flange |
Atomic H
only |
Atomic H plus
CBr4 Injector |
| RIBER |
1000/32/2300 |
DN40CF
2,75" (70mm) |
CH-RI2 |
CH-CBR-RI2 |
| EPINEAT COMPACT 21 |
DN63CF
4" (114 mm) |
CH-RIE |
CH-CBR-RIE |
DN100CF
6" (152 mm) |
CH-RIE2 |
CH-CBR-RIE2 |
| 48/49 |
DN150CF
10" (254 mm) |
CH-RI8 |
CH-CBR-RI8 |
| VG
All sources have Integrated Water Cooling (W)
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V80 |
DN63CF
4" (114 mm) |
CH-VG8W |
CH-CBR-VG8 |
| V90 |
DN63CF
4" (114 mm) |
CH-VG9W |
CH-CBR-VG9W |
| V100 |
DN100CF
6" (152 mm) |
CH-VG1W |
CH-CBR-VG1W |
| Varian / Intervac |
Gen II |
DN40CF
2,75" (70mm) |
CH-VA2 |
CH-CBR-VA2 |
| Mod Gen II |
DN63CF
4" (114 mm) |
CH-VA3 |
CH-CBR-VA3 |
Others
and manufacturers not listed above Integrated Water Cooling is a factory option (W) |
Flange Size |
DN40CF
2,75" (70 mm)
or higher |
CH-AD1 |
CH-CBR-AD1 |
| Flange Size |
DN63CF
4" (114 mm)
or higher |
CH-AD2 |
CH-CBR-AD2 |
| Flange Size |
DN100CF
6" (152 mm)
or higher |
CH-AD3 |
CH-CBR-AD3 |
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