Advantages

The use of an electron beam enables not only observation of the submicron world (TEM’s SEM’s and X-ray microanalysers) but also processing with submicron precision (electron beam lithography systems).
The optimum cathode material for use in these instruments would possess the following properties:

• Low potential barrier (work function)
• High melting point and stability at high temperatures
• Low vapor pressure so as to reduce evaporation loss
• Chemical stability

The relative drawbacks of tungsten cathodes are a work function of 4.7eV, insufficient beam current, and a short service life.

LaB6 has a work function of 2.66eV – thus more easily emitting electrons – and is a relatively stable material, so it has been increasingly used as a material for cathodes instead of tungsten.

Using LaB6 cathodes with TEM’s and SEM’s, even with the electron beam narrowed down, it is possible to obtain enough beam current to achieve better resolution and clear micrographs with less noise.
The principle advantage, however, is that LaB6 can be used in a stable condition for a much longer time.

Denka manufactures the purest, highest quality LaB6 crystals for use in their cathode tips.

Applications are:

• SEM
• TEM
• X-ray Beam Analysis (EPMA)
• Electron Beam Lithography

Benefits:

High Brightness:
A LaB6 beam is 10 times brighter than tungsten, has superior resolution, and features a wide range of acceleration voltages. It provides sharp, clear pictures, down to the smallest detail.
The initial brightness of a Denka Model 3 cathode (1 x 106A/cm2.Str) is substantially better than that of competing, mini-vogel type cathodes (typically 5 x 105A/cm2.Str).

Long Life:
Heat and vacuum are the final determinants of any cathode tip’s life, but at 1550°C and a vacuum of 10-7 Torr, a service life of about 500 hours can be expected.

Stability:
Thanks to its simple and durable construction, every Denka Model 3 LaB6 Cathode offers a stability of better than 3% per hour at 1550°C.

Interchangeability:
Denka Model 3 LaB6 cathodes are designed as direct replacements for tungsten filaments when a vacuum in the 10-7 range is provided.