The Denka M-3 LaB6 filaments are the industry standard, high quality LaB6 cathodes. The standard cathode with the 15µm round tip has a 90° tip angle, which provides a high brightness source coupled with excellent stability. Special version with sharper 60° tip angle and smaller 5µm/10µm round tipst are available for TEMs.
Denka uses the purest , high qulaity LaB6 crystals for the Denal LaB6 cathodes. The Denka LaB6 tip provides a 10x higher brightness as 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. See electron source performance table for more details. The Denka LaB6 cathodes improve results when used for:

• SEM for low voltage and long term 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 of the Denka M-3 LaB6 EM cathodes

The Denka 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 the a number of features and benefits:

• Interchangeability: Denka M-3 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 sharpere tips)
• Stable sources; due to its durable and simple construction, the standard Denka M3 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 M3 LaB6 cathode
• Low vapour pressure; reduced evaporation loss
• High melting point and stability at operating temperatures
• Low work fubction of 2.66ev (compared to 4.7ev for tungsten)

Specifications of the Denka M-3 LaB6 EM cathodes

Please consult the following table for the correct type of LaB6 source for your SEM, TEM or Microprobe. The Denka LaB6 EM cathodes are available for FEI, Hitachi, JEOL, Amray, CamScan, Philips, Tescan, Zeiss, LEO, Leica, Cambridge Instruments and Leica electron microscopes..

Type	Stand tip	Sharp tip
Tip shape	90°cone angle with 15µm round tip	60°cone angle with 5µm round tip 60°cone angle with 10µm round tip
Brightness Value	10x times than tungsten tip 1 x 106 A/cm2.Str	2x times than standard tip 2 x 106 A/cm2.Str
Saturation	Mono spot at around 1500°C	Mono spot at around 1500°C
Crossover	Small; 7-10µm	Small; 7-10µm
Angular distribution	Sharp; 1.6 x 10-2 rad	Sharp; 1.6 x 10-2 rad
Lifetime	Approx. 500 - 2000 hrs	Shorter than standard tip
Ease of operation	Moderate	Difficult due to spot adjustment
Stability	High, better than 3%/hr	Lower, due to smaller spot
Vacuum	10-7 mbar or better	10-7 mbar or better
Work function	2.66 ev	2.66 ev