Recipe for fast, energetic, neutral atoms
doi:10.1038/nindia.2013.16 Published online 1 February 2013
New research has invented a compact tabletop laser-based source of highly energetic neutral atoms1. Extremely short laser pulses were made to react with a cluster of argon atoms, generating charged ions that spawned neutral atoms when passed through ion neutralizer. These energetic neutral atoms will be very useful in fabricating novel electronic and optical devices.
Laser-generated charged particles have drawbacks as they are affected by electric and magnetic fields. This is why charged particles cannot penetrate deeper into solids to aid device fabrication. Neutral atoms offer a better option, as they remain unaffected by electric and magnetic fields. Studies trying to generate neutral atoms have been able to accelerate atoms to only millielectronvolt energeies.
In search of neutral atoms with higher energies, the researchers used high-energy ultra-short laser pulses to react with clustered argon atoms. The interaction of an intense laser pulse with an argon cluster removed as many as eight electrons from each atom in the cluster, which typically comprised about 40,000 atoms.
Clusters that had been ionized by the laser were reduced to assemblages of ions, spewing megaelectronvolt ions that then passed through an ion neutralizer, yielding highly energetic neutral atoms.
These experiments showed that under optimum conditions, conversion of ions to neutral atoms could approach 100%. The dosage and neutral atom energy can be tuned by varying cluster size and laser parameters.
Fast atoms can penetrate deeper in a charged environment and outperform charged particles in many applications such as lithography to create novel nanostructures.
The researchers say that the point-like source of fast atom beams demonstrated here could offer a promising candidate to circumvent the resolution problems of extended neutral atom sources, currently prevalent in proximity lithography.
- Rajeev, R. et al. A compact laser-driven plasma accelerator for megaelectronvolt-energy neutral atoms. Nat. Phys. (2013) doi: 10.1038/nphys2526