| |
The Gas Cracking Source - GRZ - is a thermal gas cracker which produces an absolutely
ion-free hydrogen gas beam to avoid ion induced damage of the substrate.High temperatures (up to 1750°C on the TC) are provided
by a tungsten filament, which is directly mounted into a gas flow line. The H2 gas is in direct contact with the hot filament
and is cracked on the filaments' surface.
This design provides high cracking efficiency at high filament temperatures while the
gas line remains colder. Due to the distance between the filament and the TC, the real temperature of the filament is much
hotter (>2000°C) than it is measured on the TC. The gas cracking cell GRZ 40-K is designed with refractory metals within the
hottest zone of the cell and therefore provides a high purity operation even at highest temperatures. The higher filament
temperature increases the cracking efficiency, whilst the integrated cooling keeps the heat load on your MBE system to a
minimum.We recommend to use the GRZ with an all metal leak valve and a gas purifying system to achieve high purity operation.
The H2 flow rates will vary according to the system and application. Beam equivalent pressures of 10-7-10-6 Torr are
frequently reported, and flow rates of 0.2-0.3 standard cm³/min are typical for many applications. The beam equivalent
hydrogen pressure should not exceed 10-5 Torr.
| |
Main parts of the GRZ |
|
