Denka M-3 LaB6 EM cathodes
Denka M-3 LaB6 EM cathodes
High brightness, direct replacement electron sources
Denka M3 LaB6 cathode. LaB6 crystal with
standard
90 degree angle and 15 µm round tip.
Introduction
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 |
Brightness |
10x times than tungsten tip |
2x times than standard tip |
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 |
12.0 |
1.0 |
6.45 |
|
AmRay /AMR (except 1200 series) |
26.0 |
1.0 |
5.0 |
|
Cambridge Instruments (except S4-10) |
12.0 |
1.0 |
6.45 |
|
CamScan with AEI conversion |
12.0 |
1.0 |
6.45 |
|
FEI TEM and SEM |
26.0 |
1.0 |
5.0 |
|
Hitachi S-Type |
9.8 |
1.2 |
2.7 |
|
JEOL K-Type metal ring - SEM - standard tip |
28.0 |
1.2 |
8.0 |
|
JEOL K-Type metal ring - TEM - sharp tip |
28.0 |
1.2 |
8.0 |
|
Leica |
12.0 |
1.0 |
6.45 |
|
LEO 400 and 1400 Series SEM |
12.0 |
1.0 |
6.45 |
|
LEO1450 (except AEI conversions) |
19.8 |
1.0 |
5.0 |
|
LEO TEM |
19.8 |
1.0 |
5.0 |
|
Philips TEM and SEM (except XL-30) |
26.0 |
1.0 |
5.0 |
|
Tescan |
19.8 |
1.0 |
5.0 |
|
Zeiss DSM and TEM |
19.8 |
1.0 |
5.0 |
Ordering Information for Denka M-3 LaB6 EM cathodes
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Electron Source Performance Table
The electron source performance table is provided to give additional information into 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 |
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|
|
|
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 |
Stability |
Standard |
High |
Very high |
Low |
X-ray analysis |
EDS / WDS |
EDS / WDS |
EDS / WDS |
EDS |
