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Kimball laB6 cathodes

Kimball lanthanum hexaboride LaB6 filaments are the industry standard, high quality LaB6 cathodes and  available for most makes of electron microscopes and other E-beam instruments.

Kimball 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

 

Kimball LaB6 cathodes are available with three types of LaB6 tips:

  1. Standard tip with 90° cone and 15 µm micro-flat for standard SEM and standard TEM applications
  2. Long life, high stability tip with 90° cone and 20 µm micro-flat for Microprobes and analytical SEM applications 
  3. High brightness, sharp tip with 60° cone and 6 µm micro-flat for high resolution TEM applications

LaB6 cathode sources need a higher operating pressure than standard tungsten sources which generally requires an additional ion-getter pump at the electron source. The required vacuum is in the 10-7mbar range. The lifetime of an LaB6 cathode is much longer than a tungsten source providing a stable high brightness source over a longer period.

The standard LaB6 cathode comprises a 90° tip angle and a 15µm flat made from a <100> oriented single crystal. This provides a long lifetime, high brightness source coupled with excellent stability.  A special version with a sharper 60° tip angle and smaller 6µm flat is available for TEMs.

Kimball Physics use the purest, high quality lanthanum hexaboride crystals for  ES-423E LaB6 cathodes. The standard Kimball LaB6 tip provides a ten times higher brightness than the standard tungsten source, resulting in better resolution with clear images and reduced noise.

For details, specifications and comparisions, please see the drop down tabs below

For tungsten filaments please see EBS tungsten filaments.

Kimball Physics ES-423E (extended life) LaB6 cathode is a high performance, resistively heated, thermionic electron source. It is based on a well proven carbon rod heater structure with improved stability, improved reliability and less exposure of the LaB6 crystal to reduce contamination of the Wehnelt aperture. There is heating current through the LaB6 crystal; there are no high-temperature current carrying joints. The LaB6 crystal is held in place by a carbon ferrule. The design results in a small physical size which fits most Wehnelt cylinder with ease.   Benefits of this unique construction are:

  • Suitable for SEM, TEM, Microprobes and E-Beam lithography systems
  • Resistively, indirectly heated high purity LaB6 crystal, resulting in lower heating current
  • High thermal stability to eliminate drift problems
  • Carbon ferrule with less exposure of LaB6 crystal to reduce Wehnelt contamination
  • low vapour pressure with reduced evaporation loss
  • High brightness; about 10 x higher than tungsten filaments (even 20x for the sharper tips)
  • Stable sources; due to its sturdy construction, the standard Kimball LaB6 cathodes comprise a stability of better than 3%/hour at 1550°C
  • Long life; at 10-7mbar vacuum and 1550°C operating temperature, >500 hours lifetime can be expected for the standard Kimball ES-423E LaB6 cathode
  • Low work function of 2.66ev (compared to 4.7ev for tungsten)

Please consult the following table for the correct type of Kimball LaB6 source or cathode for your SEM, TEM or Microprobe. The Kimball Physics LAB6 cathodes are available for Thermo, FEI, Hitachi, JEOL, Amray, CamScan, ISI, ABT, Topcon, Philips, Tescan, Zeiss, LEO, Leica, Cambridge Instruments and Leica electron microscopes.

Type Standard tip Long life, high stability tip High brightness sharp tip
Tip shape 90°tip angle with 15µm flat 90°tip angle with 20µm flat 60°tip angle with 6µm flat
Brightness
Value		 10 x times than tungsten tip
1 x 106 A/cm2.Str		 2 x less than standard tip
0.5 x 106 A/cm2.Str		 2 x times than standard tip
2 x 106 A/cm2.Str
Saturation Mono spot at around 1550°C Mono spot at around 1550°C Mono spot at around 1550°C
Crossover Small: 7-10µm Small: 7-10µm Small: 7-10µm
Angular distribution Sharp: 1.6 x 10-2 rad Sharp; 1.6 x 10-2 rad Sharp; 1.6 x 10-2 rad
Lifetime Long > 500 hrs Longer than standard tip Shorter than standard tip
Ease of operation Moderate Easy, due to larger spot Difficult, due smaller spot
Stability High, better than 3%/hr High, better than 3%/hr Lower, due to smaller spot
Vacuum 10-7 mbar or better 10-7mbar or better 10-7mbar or better
Work function 2.66 ev 2.66 ev 2.66 ev
Application SEM & TEM Analytical SEM / Microprobe TEM

 

 

Electron Microscope Type or Filament base Product number Ceramic Disc mm Pin Diameter  mm Pin Pitch mm
AEI 14-AE3501 12.0 1.0 6.45
AmRay /AMR (except 1200 series) 14-AM3502 26.0 1.0 5.0
Cambridge Instruments (except S4-10) 14-AE3501 12.0 1.0 6.45
CamScan with AEI conversion 14-AE3501 12.0 1.0 6.45
FEI TEM and SEM 14-FP3503 / 14-FP3568 26.0 1.0 5.0
Hitachi S-Type 14-HI3504 9.8 1.2 2.7
JEOL K-Type metal ring – SEM – standard tip 14-JL3508 28.0 1.2 8.0
JEOL K-Type metal ring – TEM – sharp tip 14-JL3568 28.0 1.2 8.0
Leica 14-AE3501 12.0 1.0 6.45
LEO 400 and 1400 Series SEM 14-AE3501 12.0 1.0 6.45
LEO1450 (except AEI conversions) 14-ZS3510 19.8 1.0 5.0
LEO TEM 14-ZS3560 19.8 1.0 5.0
Philips SEM and TEM (except XL-30) 14-FP3503 / 14-FP3563 26.0 1.0 5.0
Philips XL-30 SEM 14-AE3501 12.0 1.0 6.45
Tescan 14-TN3509 19.8 1.0 5.0
Thermo SEM and TEM 14-FP3503 / 14-FP3563 26.0 1.0 5.0
Zeiss DSM SEM and TEM 14-ZS3510 / 14-ZS3560 19.8 1.0 5.0

This electron source performance table is provided to give additional information on the performance and requirements for different type of electron emitters. Tungsten cathodes are still used in many SEMs. Improved results can be obtained with LaB6 cathodes. The highest resolution, highest brightness and best low kV performance can be achieved with either Schottky or cold Field Emission Sources.

Emitter Type

Thermionic

Thermionic

 Schottky TFE

Cold FE
Tip image comparison Thermionic Wolframe Cathode Thermionic LaB6 Cathode chottky TFE ZrO/W (100) Cathode Cold Fe W (310) cathode
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) 1×104 1×105 1×107 2×107
Maximum probe current (nA) 1000 1000 10 0.2
Energy epread @ 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
Stability Standard High Very high Low
X-ray analysis EDS / WDS EDS / WDS EDS / WDS EDS

Further details and specifications of  Kimball ES423E LaB6 can be found in the PDF: Kimball ES-423E Extended Life LaB6 Cathode Specifications

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