Cathodes & Filaments for Electron Microscopes Denka Model 3s LaB6 Cathodes


Cathodes, LaB6 n


Lanthanum Hexaboride is the optimum cathode material for use in:


• SEM • TEM • X-Ray Microanalysis


• Electron Beam Lithography


Features • Low potential barrier (work function) • High melting point and stability at high temperatures • Low vapor pressure – reduces evaporation lost • Chemical stability


• High brightness: LaB6 beam is ten times brighter than tungsten, has superior resolution – wide range of acceleration voltages. It provides sharp and clear pictures even to the smallest details. The initial brightness of a Denka Model 3 cathode (1 x 106


A/cm2


that of competing mini-vogel type cathodes (typically 5x105


.Str)


.Str) is substantially better than A/cm2


• Long life: Heat and vacuum are the final determinants of any cathode tip’s life, but at 1550°C and a vacuum of 10-7


Torr, a service life of about 500 hours can be achieved.


• Stability: Every Denka Model 3 cathode offers a stability of better than 3% per hour at 1550°C


• Interchangeability: Denka Model3 LaB6 cathodes are designed as direct replacement for tungsten filaments.


Specifications Brightness


Saturation Crossover


Angular distribution Used Temperature Lifetime


Operation Stability Technology Needed 4 Flat Tip


About 5 times that of tungsten, 2-5 x 105


A/cm2 · Str


Mono spot at about 1,400°C Large (11-13µ)


Broad, 3.3-4.2 x 10-2 Low temperature


rad


Tip Selection Standard (Round) Tips


Provided with a 90° cone and 15µ radius round tip. 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 40µ radius 60µ radius 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


Standard (Round) Tip


About 10 times that of tungsten, 1x106


A/cm2 · Str


Mono spot at about 1,500°C. Small (7-10µ)


Sharp, 1.6 x 10-2 Low temperature


Easy, thanks to its large spot size and broad adjusting range.


High, vulnerable to thermal expansion or vibration.


Ordinary Not so difficult. High High rad


Long life, usable at low temperatures Long life but shorter than flat tips. and crystallized end changes slowly.


60° Cone Angle 10µ radius


Sharp Tip


Twice as bright as standard tips, 2 x 106


A/cm2 · Str


Almost the same as standard tips Small (7-10µ)


Sharp, 1.6 x 10-2 High temperature. Short


rad


60° Cone Angle 20µ radius 40µ radius 60µ radius 100µ radius


Difficult; Point adjustment needed! Middle, vulnerable to the thermal


expansion or vibration. Adjustment is sometimes necessary.


Very high


Electron Microscopy Sciences In PA: (215) 412-8400 • Toll-Free (800) 523-5874 Fax (215) 412-8450 or 8452 • email: info@emsdiasum.com


or stacie@ems-secure.com • www.emsdiasu m.com


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