Filaments and Cathodes for Electron Microscopes
Overview
Rave Scientific offers a wide variety of electron microscope emitters. Our Tungsten, Lab6 and Schottky emitters are compatible with all major brands of scanning and transmission electron microscopes, including all FIB-SEM workstations. Our emitters are of high quality and are manufactured to exceed the specifications of the original equipment manufacturers. The following Electron Source Performance Table is provided to give you additional information regarding the performance and requirements for different types of electron emitters. Tungsten cathodes are still used in the majority of all SEMs and in general use TEMs. Improved results can be obtained with LaB6 cathodes, whereas the highest resolution can be obtained with either Schottky or cold Field Emission Sources which can only be used in suitable EMs.
| Emitter Type | Thermionic | Thermionic | Schottky FE | Cold FE |
|---|---|---|---|---|
| Cathode Material | W | LaB6 | ZrO/W (100) | W (310) |
| Operating Temp (K) | 2700 | 1800 | 1800 | 300 |
| Cathode Radius (nm) | 60,000 | 10,000 | <1000 | <100 |
| Effective Source Radius (µm) | 25 | 10 | 0.015 | 0.0025 |
| Emission Current Density (A/cm2) | 3 | 30 | 5300 | 17,000 |
| Total Emission Current (µA) | 200 | 80 | 200 | 5 |
| Brightness (A/cm2.sr.kV) | 1x104 | 1x105 | 1x107 | 2x107 |
| Maximum Probe Current (nA) | 1000 | 1000 | 10 | 0.2 |
| Energy Spread @ Cathode (ev) | 0.59 | 0.4 | 0.31 | 0.26 |
| Energy Spread @ Source Exit (eV) | 1.5 – 2.5 | 1.3 – 2.5 | 0.35 – 0.7 | 0.3 – 0.7 |
| Beam Noise (%) | 1 | 1 | 1 | 5 – 10 |
| Emission Current Drift (%/h) | 0.1 | 0.2 | <0.5 | 5 |
| Operating Vacuum (hPa/mbar) | <10-5 | <10-6 | <10-8 | <10-10 |
| Typical Cathode Life (h) | 100 | >1000 | >5000 | >2000 |
| Cathode Regeneration (h) | None | None | None | 6-12 |
| Sensitivity to External Influences | Minimal | Low | Low | High |