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TOOLS & INSTRUMENTS

Atom Probe Tomography (LEAP 4000X Si/HR – Local Electrode Atom Probe)

atomprobe1

LEAP 4000X Si/HR

  • Imaging time-of-flight mass spectrometer and field ion microscope.
  • Can deliver 3-D, isotopically- and chemically- resolved images
  • Sub-nanometer spatial resolution possible
  • High combined efficiency (100% ionization / 55% detection)
  • High Sensitivity (approx. 10 ppm at.)
  • Typical analysis volume approx. 100 nm x 100 nm x 300 nm.
  • No matrix corrections or sensitivity factors required for quantification

Specifications/Capabilities

How it Works

Imaging Time-of-Flight graphic
Graphical representation of local electrode time-of-flight process.
  • Atom probe tomography requires samples that are small and needle-like in form. Typically, we prepare the samples in our dual beam FIB/SEM instrument via in-situ, site-specific lift out.
  • The sample is loaded into the LEAP analysis chamber, cooled to cryogenic temperatures, and positioned in front of a local electrode.
  • A high electric potential is applied between the sample and the local electrode to promote field evaporation and to accelerate any ions down the flight path and towards a 2-dimensional position sensitive detector.
  • Data acquisition proceeds by subjecting the sample to repeated pulses, either voltage or thermal (UV laser), to trigger the controlled field evaporation of ions from the sample tip.
  • The detector records the time-of-flight and the X and Y impact position on the detector for each ion. Using this information, the identity of each ion is known (mass-to-charge state ratio) and the point of origin on the sample surface can be determined. The Z depth for each ion is determined by order of arrival.
  • A 3-D reconstruction of the sample is generated, atom-by-atom, by computer.

 Typical Outputs

  • 3-D, chemically- and isotopically- resolved images
Atom Probe 3D reconstruction graphic
3-D reconstruction of Al-In-Ga-As sample showing < 6 nm thick buried layers enriched in Aluminum and depleted in Indium.
  • Time-of-flight and mass spectra
Mass spectrum of uranium oxide reference material.
Mass spectrum of uranium oxide reference material.

Site-Specific Atom Probe Sample Preparation via Dual Beam FIB-SEM

FIB sample preparation steps
A. Deposit a protective platinum cap on the surface of the specimen and on top of the region of interest. B,C,D. Use the ion beam to remove material around the region of interest. E. Attach the in-situ micromanipulator to the free end of the sample. F. Cut the sample loose and lift the sample from the bulk specimen material.
FIB sample preparation steps part 2
G. Attach a piece of the sample to an atom probe sample support post and cut the mounted piece free. H. Deposit additional Pt around the base of the sample to secure the mounting. I. Use the ion beam to mill the sample into a needle-like shape. J. Use the ion beam to mill the sample into a needle-like shape. K. The sample is ready for the atom probe. L. Repeat steps G through K for the remaining lift-out material to generate additional atom probe samples.

 

 

Usage Information

Access Information

Collaborative research projects are possible when the work is consistent with the Materials Measurement Science Division mission and interests. Please contact us to discuss possible collaborations.

Analytical chemistry, Materials characterization, Composition and structure and Nanometrology
Created January 11, 2012, Updated May 15, 2023