LaB6 filaments includes a 90° tip angle and a 15µm round tip; this provides a high brightness source coupled with excellent stability. They made from the purest, highest quality LaB6 crystals. The LaB6 tip provides a 10x higher brightness than the standard tungsten source, resulting in better resolution with clear images and less noise. The lifetime of the LaB6 cathode is much longer than a tungsten source providing a stable source over a longer period. The LaB6 cathodes improve results when used for:
- SEM for low voltage and long term EDS mapping applications
- TEM imaging and analysis
- Electron probe micro analyzers (EPMA or Microprobe)
- E-beam lithography
The LaB6 sources require a higher vacuum than standard tungsten sources which generally requires an additional ion-getter pump at the electron source. The required vacuum is in the 10-7 mbar range.
Design and features
The LaB6 EM cathode construction is similar to the tungsten cathodes. It uses the same base with tungsten wires attached to the contact pins. Instead of a full tungsten loop, the LaB6 crystal forms the tip with the tungsten wires cemented against the LaB6 crystal. In this design the LaB6 crystal is directly heated by the filament current through the tungsten wires and the LaB6 crystal.
This unique construction has a number of features and benefits:
- Interchangeability LaB6 cathodes are designed as direct replacement for tungsten filaments
- Suitable for SEM and TEM
- Direct heating design with tungsten wired cemented at the high purity LaB6 crystal
- High brightness; about 10x higher than tungsten filaments (even 20x for the sharper tips)
- Stable sources; due to its durable and simple construction, the LaB6 comprises a stability of better than 3%/hour at 1550°C
- Long life; at 10-7mbar vacuum and 1550°C operating temperature, 500-2000 hours lifetime can be expected for the standard LaB6 cathode
- Low vapour pressure; reduced evaporation loss
- High melting point and stability at operating temperatures
- Low work function of 2.66ev (compared to 4.7ev for tungsten)