Light emitted from a sample irradiated by an electron beam is analyzed by an optical spectrometer. The technique provides valuable information concerning the band structure and energy levels of the sample. Short electron beam pulses are used to measure the decay of light emission and the life time of energy levels. A bright, well focused electron beam is required for excitation. Light from the filament inside the gun should be blocked in order not to interfere with the luminescence signal.
The Black Gun Concept
S T A I B INSTRUMENTS offers a complete family of guns for cathodoluminescence applications. The special "black gun" design offers complete optical isolation of the gun. An optical dump and a 90 degree deflection of the electron beam ensure that virtually no photons from the gun can reach the sample. Most guns can be equipped with "black gun" and beam pulsing options as shown in the product table. A wide range of adapter flanges is available, such as Cu gasket, Viton rings, metal wire or custom designed flanges. The electron gun operates with vacuum levels of less than 10-5 Torr. Differential pumping is available for higher pressures in the sample chamber.
In-situ Photoluminescence and RHEED
In-situ cathodoluminescence is particularly attractive as it can be combined with RHEED analysis using the same electron gun for both techniques. An optical system of lenses is used to collect the light emitted from the sample and guided to a spectrometer. The system can be retracted during sample growth.
| Product list of guns for Cathodoluminescence | |||
| Designation | Energy | Beam current | Beam pulsing options* |
| CL-5 | 5,000 eV | 50 µA | 30 ns to 1 ms |
| CL-12 | 12,000 eV | 100 µA | 1 µs to 10 ms |
| CL-15 | 15,000 eV | 120 µA | 1 µs to 10 ms |
| CL-20 | 20,000 eV | 120 µA | 3 µs to 20 ms |
| CL-30 | 30,000 eV | 120 µA | 5 µs to 30 ms |
| CL-50 | 50,000 eV | 120 µA | 10 µs to 30 ms |
| * other pulsing speeds are available upon reques | |||
