Accelerated Neutral Atom Beam (ANAB)
Accelerated Neutral Atom Beam (ANAB) technology is a low energy accelerated particle beam gaining acceptance as a tool for nano-scale surface modification in such diverse areas as implantable medical devices, semiconductor manufacturing, and optics. ANAB is created by acceleration of neutral argon (Ar) or other gas atoms with very low energies under vacuum which bombard a material surface, modifying it to a shallow depth of 2-3 nm.
To create ANAB, a stream of clusters is formed via adiabatic expansion of pressurized gas into vacuum through a specially shaped nozzle. Clusters of 500-5,000 atoms (approximately spherical in shape, 1-4 nm diameter) are formed, bound by van der Waals forces. The clusters are then ionized by electron impact ionization and accelerated to energies from 20-50 kV. Cluster dissociation is then promoted by orchestrating cluster collisions with slow-moving gas molecules present along the flight path. Finally, all charged species are removed from the beam by an electrostatic deflector.
The resulting beam contains accelerated neutral atoms with controllable energies from ~10 eV to ~100eV. With ANAB, the dissociated clusters form “clouds” of individual gas atoms or molecules traveling in close proximity to each other with essentially the same speed and direction and arriving nearly simultaneously to the target surface.
ANAB technology can impart beneficial functionality on metal, ceramic, glass, and polymer surfaces without detrimental impacts of traditional surface modification techniques such as plasma and ion beam technologies. ANAB provides an intense, collimated beam of energetic neutral gas atoms with highly controlled energies from 10-100eV per atom, an ideal range for many nanoscale surface modifications.
- Gas cluster formation ①
- Cluster ionization ② and acceleration ③
- Cluster dissociation ④ and deflection ⑤
- Beam collides with surface and modifies it ⑥
|Energy range:||10 eV – 100 eV per atom|
|Atom velocity:||5 – 15 km/sec|
|Atom Flux:||1015 – 1016 atoms/cm2/sec (equivalent to 0.1 – 1 mA for an ionized beam)|
|Beam diameter:||~1 cm|
|Beam divergence angle:||0.15 degrees|
|Base pressure:||<10-6 Torr|
|Beamline pressure:||~5*10-5 Torr|
|Gas species:||Ar, O2, N2, CH4, B2H6, PH3, AsH3, SiH4, GeH4, NF3, CF4, SF6, …|
Key ANAB characteristics:
- True nano-scale modification: 0.5 – 3 nm
- Non-additive technology
- Surface modification without subsurface damage
- Electrically neutral beam – avoids surface damage
- The beam can be modified (energy, flux, chemistry) to achieve specific objectives