Denka M-3 LaB6 EM cathodes
High brightness, direct replacement electron sources

Denka M-3 LaB6 EM cathodes   |   Denka LaB Filaments Selection Table   |   Electron Source Performance table

 Introduction

Denka M3 LaB6 cathode. LaB6 crystal with standard  90 degree tip and 15µm flat.

The Denka M-3 LaB6 filaments are the industry standard, high quality LaB6 cathodes. The standard cathode with the round tip has a 90° tip angle and a 15µm flat, which provides a high brightness source coupled with excellent stability.  Special version with  sharper 60° tip angle and smaller 5µm/10µm flat 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..

Denka M-3 LaB6 EM cathode selection table

Electron Source Performance Table

The electron source performance table is porvided to give additional information into the performance and requirements for different type of electron emitters. Tungsten cathodes are still used in the majority in SEMs. Improved results can be obtained with LaB6 cathodes and the highest resolution can be obtained with either Schottky or cold Field Emission Sources