Laser Cooled Atoms as a Focused Ion Beam Source

 

James L. Hanssen and Jabez J. McClelland

 

Electron Physics Group, National Institute of Standards and Technology, Gaithersburg, MD, 20899-8412 USA

 

We propose a method to create a focused ion beam using laser cooled atoms as an ion source.  Laser cooled atoms provide a compact source of atoms with temperatures on the order of 100 mK or lower.  If these atoms are then subjected to a photo-ionization laser pulse, they become a compact source of nearly mono-energetic ions.  By applying a potential gradient, the ions are extracted to form a beam that can be focused via standard ion optical techniques.  Based on the small initial size of the ion cloud as well as the narrow energy distribution, it should be possible to focus the beam to a spot size of ~10 nm.  In addition to providing a spot resolution comparable to the state of the art in focused ion beams, this technique will widen the range of ions that can be used to create such beams.  Furthermore, additional tools available for laser cooling atoms open the door for more exotic ion beams.  For instance, the atom-on-demand technique[1] can be used to create an ion-on-demand beam which would allow for single ion doping of materials. 

 

            Current work consists of creating an experimental realization of the focused ion beam.  A chromium mirror magneto-optical trap (MOT)[2] using a mirror with a hole is being constructed.  The mirror serves the dual purpose of being an optical element of the MOT as well as forming an electrostatic lens for focusing the ion beam.  The generated ions will be observed using a channeltron operating in pulse detection mode.  Once the beam is made, the focus resolution will be measured using a TEM calibration specimen.  Current experimental progress on the focused ion will be presented as well as numerical simulations of the achievable resolution of the system.

 

Name:              James Hanssen

Mentor:            Jabez McClelland

Division:           Electron and Optical Physics (841)

Laboratory:      Physics

Building:           216

Room:              A247

Mail Stop:        8412

Telephone:        301-9753768

Fax:                  301-926-2746

Email:               james.hanssen@nist.gov

Sigma Xi:          not a member

Category:         Physics



[1] Atoms on Demand: Fast, Deterministic Production of Single Cr Atoms, S.B. Hill and J.J. McClelland, Appl. Phys. Lett. 82(18), 3028-3031 (2003)

[2] Realization of a Mirror Magneto-optical Trap, M. A. Clifford et al, J. Mod. Opt. 48(6), 1123-1128 (2001)