Posted: October 21, 2008

Buckyball beams

(Nanowerk News) Once computer chip manufacturers have made their multi-layered structures, it is also necessary for them to verify precisely that the layers are composed in the proper way. One way of doing this is to shoot beams of ions which, like meteorites striking the Moon, eject material that can be characterized using mass spectrometry, providing information about subsurface layering.
Just as large meteorites make bigger dust clouds, large molecules or clusters of atoms are better at ejecting materials than single-atom ions since the clusters excavate more cleanly and provide more unambiguous signs of deep structure in the sample being imaged.
The lab of Nick Winograd of Pennsylvania State University has pioneered the use of beams of carbon-60 molecules (buckyballs). At the AVS 55th International Symposium & Exhibition, Winograd will describe how he and his students have greatly improved the sensitivity of detection of the ejected material by using an infrared laser for photoionization prior to analysis by the mass spectrometer. The infrared laser is effective since electrons can be removed from molecules with high efficiency via tunneling and without significant photofragmentation. For pictures illustrating the difference between single atom probes and C60 beams, see:
Winograd's talk, "Strong Field Laser Postionization Imaging and Depth Profiling Using C60 Cluster Ion Beams" is at 11:00 a.m. on Tuesday October 21, 2008, in Room 207 of the Hynes Convention Center.
Source: American Institute of Physics
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