Denka LaB6 Cathodes

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 M-3 LaB6 EM cathodes

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..

Type

Stand tip

Sharp tip

Tip shape

90°cone angle with 15µm tip flat

60°cone angle with 5µm tip flat 
60°cone angle with 10µm tip flat

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

 

Denka M-3 LaB6 EM cathode selection table

Electron Microscope Type or Filament base

Product number

Ceramic Disc mm

Pin Diameter  mm

Pin Pitch mm

AEI

AU-14-AE3301

12.0

1.0

6.45

AmRay /AMR (except 1200 series)

AU-14-AM3302

26.0

1.0

5.0

Cambridge Instruments (except S4-10)

AU-14-AE3301

12.0

1.0

6.45

CamScan with AEI conversion

AU-14-AE3301

12.0

1.0

6.45

FEI TEM and SEM

AU-14-FP3303

26.0

1.0

5.0

Hitachi S-Type

AU-14-HI3304

9.8

1.2

2.7

JEOL K-Type metal ring - SEM - standard tip

AU-14-JL3308

28.0

1.2

8.0

JEOL K-Type metal ring - TEM - sharp tip

AU-14-JL3318 / AU-14-JL3328

28.0

1.2

8.0

Leica

AU-14-AE3301

12.0

1.0

6.45

LEO 400 and 1400 Series SEM

AU-14-AE3301

12.0

1.0

6.45

LEO1450 (except AEI conversions)

AU-14-ZS3310

19.8

1.0

5.0

LEO TEM

AU-14-ZS3310

19.8

1.0

5.0

Philips TEM and SEM (except XL-30)

AU-14-FP3303

26.0

1.0

5.0

Tescan

AU-14-TN3309

19.8

1.0

5.0

Zeiss DSM and TEM

AU-14-ZS3310

19.8

1.0

5.0

 

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

Emitter Type Thermionic Thermionic Schottky FE Cold FE
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) 1x104 1x105 1x107 2x107
Maximum Probe Current (nA) 1000 1000 10 0.2
Energy Spread @ 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

9 Item(s)

9 Item(s)