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NIST has created a new laser-assisted atom probe tomography (L-APT) tool.  This tool uses photoionization at extreme ultra-violet (EUV) laser photon energies in the approximate range of 10 - 100 eV to promote photoionization and photo-disassociation  of atomic species and molecular complexes that comprise the nano-needle-shaped  specimen under examination.  This new approach employs a completely different means for ionizing atomic species than what is used in conventional L-APT tools. In conventional approaches, thermal pulses imparted on the specimen tip from a pulsed visible/near-ultra-violet  laser decrease the activation energy barrier for field evaporation of ions while the specimen is subjected to a strong electric field. Conventional L-APT is problematic since for a given applied field, evaporation efficiency under these conditions varies strongly depending upon the chemical composition of the specimen under examination as well as the location of an atom on the physical surface of the specimen.  

The new NIST system represents a great improvement since it will employ an alternative pathway to field evaporation via direct photo-ionization of all chemical species.  This feature will promote efficient single-atom photoionization across the periodic table, which will help mitigate ambiguous chemical assignments that plague current thermally-driven processes. The system also will incorporate in situ electron-beam imaging of the specimen that will provide near-real-time measurement of the specimen shape.  This dimensional information will be fed immediately to reconstrnction and analysis algorithms without the need to interrupt data collection or dismount the sample.  This new approach (incorporating both photoionization via an EUV laser and in situ specimen tip shape evaluation) to L-APT will offer substantially more reliable and faster analysis than what is currently possible.

The figure below is the hybrid EUV imaging spectrometer where the numbers correspond to the various parts of this invention: sample (106), tip of sample (180), electron micrograph (182), primary electrons (110), pulse EUV radation (104), aperture (153), wall (154), ion trajectory (113), ion detection (114), photoions (112), extraction electrode (150), scattered electrons (116), electron diffraction (184),  and ion time-of-flight mass spectrometry (186).


The invention is a laser-assisted atom probe tomography instrument (L-APT). This instrument would utilize photoionization at extreme ultra-violet (EUV) laser photon energies in the approximate range of 10 eV to 100 eV to promote photoionization and photodisassociation of atomic species and molecular complexes that comprise the nano-needle-shaped specimen under examination.

David Diercks, Norman Sanford, Ann Chiaramonti Debay, Brian Gorman
Patent Number: 
Technology Type(s): 
Nano-Technology Ion Storage, Laser and Optics, Laser Applications, Analytical Chemistry, Atomic Physics, Atomic Spectroscopy, Biochemical Science, Chemical Physics, Chemical Sciences, Photon Physics, Physical and Chemical Properties,
Internal Laboratory Ref #: 
Patent Issue Date: 
April 10, 2018
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