Filaments
LaB6 Filaments
Denka Model 3 LAB6 Filaments
Advantages of LaB6 Filaments
The use of an electron beam enables not only observation of the submicron world (TEMs, SEMs, and X-ray microanalyzers) but also processing with submicron precision (electron beam lithography systems). The optimum filament material for use in these instruments would possess the following properties:
- Low potential barrier (work function)
- High melting point and stability at high temperatures
- Low vapor pressure so as to reduce evaporation loss
- Chemical stability
The relative drawbacks of tungsten filaments are: work function of 4.7eV, insufficient beam current density, and a short service life. LaB has a work function of 2.66eV, thus easily emitting electrons, and is a relatively stable material, so it has been increasingly used as a material in filaments in preference to tungsten. Using LaB6 filaments with TEMs and SEMs, even with the electron beam narrowed down, it is possible to obtain enough beam current density to achieve better resolution and clear photographs with less noise. The principle advantage, however, is that LaB6 can be used in a stable condition for a much longer time.
Denka manufactures the industry's purest, highest quality LaB6 crystals for use in their filament tips, featuring:
- High Brightness: A LaB6 beam is ten times brighter than tungsten, has superior resolution, and features a wide range of acceleration voltages. It provides sharp, clear pictures down to the smallest detail. The initial brightness of a Denka Model 3 filament (1X10 A/cm2. Str) is substantially better than that of competing, minivogel type filaments (typically 5X10 A/cm²-Str).
- Long Life: Heat and vacuum are the final determinants of any filament tip's life, but at 1550° C and a vacuum of 10 Torr, a service life of about 500 hours can be expected.
- Stability: Thanks to its simple and durable construction, every Denka Model 3 LaB Filament offers a stability of better than 3% per hour at 1550°
- Interchangeability:Denka Model 3 LaB6 filaments are designed as direct replacements for tungsten filaments.
Standard Denka M-3 Filaments
Provided with a 90° cone angle and 15µ radius round tip.
| Cat # | Description | Price |
|---|---|---|
| A40005 | JEOL | $1,307.10 |
| A4005-H60 | JEOL | $1,389.60 |
| A40010 | Philips | $1,378.40 |
| A40011 | Philips | $1,286.50 |
| A40015 | AMRAY | $1,001.40 |
| A40020 | Cambridge | $1,200.60 |
| A40021 | Cambridge | $1,389.60 |
| A40022 | Cambridge | $1,424.00 |
| A40025 | Hitachi | $1,195.60 |
| A40030 | ELECTROSCAN | POR |
| A40035 | ISI SEMs (except DS-130) | $1,195.60 |
| A40040 | ISI TEMs | $1,195.60 |
| A40041 | ZEISS | $1,342.30 |
Flat (Truncated) Tips
Flat tips are recommended for applications where stability and long lifetime are the prime considerations, and where some degree of brightness can be sacrificed. Flat tips are available in eight configurations:
| 90° Cone angle 20µ radius | 60° Cone angle 20µ radius |
| 90° Cone angle 40µ radius | 60° Cone angle 40µ radius |
| 90° Cone angle 60µ radius | 60° Cone angle 60µ radius |
| 90° Cone angle 100µ radius | 60° Cone angle 100µ radius |
Sharp Tips
Sharp tips are recommended for applications where initial brightness is the foremost consideration and where shorter lifetime can be accepted. Sharp tips are available in two configurations:
| 60° Cone angle 5µ radius | 60° Cone angle 10µ radius |
Denka M-3 LaB6 filaments A40005 to A40040 are available in flat & sharp tip configurations.
Please call or email Soquelec for more information.
Comparison of Tip Configurations Available with Denka M-3 LaB6 Filaments
| Flat Tip | Standard (Round) Tip | Sharp Tip | |
|---|---|---|---|
| Brightness | About 5 times tdat of tungsten 2-5 x 10 A/cm Str | About 10 times tdat of tungsten 1 x 10 A/cm Str | Twice as bright as standard tips 2 x 10 A/cm Str |
| Saturation | Mono spot at about 1400° C | Mono spot at about 1500° C | Almost tde same as standard tips |
| Crossover | Large (11-13µm) | Small (7-10µm) | Small (7-10µm) |
| Angular Distribution | Broad 3.3-4.2 x 10 rad | Sharp 1.6 x 10 rad | Sharp 1.6 x 10 rad |
| Used Temperature | Low Temperature | High Temperature | High Temperature |
| Lifetime | Long life (usable at low temperatures,and crystalized end changes slowly) | Long life (but shorter tdan flat tips) | Short |
| Operation | Easy (tdanks to its large spot size and broad adjusting range) | Not so difficult | Difficult (tde point adjustment needed) |
| Stability | High (invulnerable to tdermal expansion or vibration) | High | Middle (vulnerable to tde tdermal expansion or vibration. Adjustment is sometimes necessary) |
| Technology Needed | Ordinary | High | Very high |
 |
 |
 |