Imago 2007 Meeting

From Northwestern University Center for Atom-Probe Tomography
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Laser pulsing applications

Semiconductor heterostructures (Praneet & Dan)

They have what should be abrupt axial and radial interfaces. We think we may be seeing preferential evaporation on one side of the sample, as well as blurred interfaces. There also have been some anomalies in reconstruction to address, including unphysical mass spectra. Discuss the possibility of spatial biasing of atom probe runs as a result of the laser.

Spatial biasing (Dan?)

Laser heating artifacts

and Imago's experiences with handling it.

Where is the laser in DAVis?

Definitively identify where the laser is impacting the sample in the DAVIS histogram, both in the current setup and the old setup.

Alternative designs

  • Would it be possible to incorporate an optics system whereby alternate pulses of the laser strike the tip from different angles or multiple directions simultaneously?
  • What would be the influence of switching to a femtosecond laser?
  • Would it be possible to have an auto evaporation control linked to both DC voltage and laser pulse energy? That is, control the evaporation rate with laser energy and maintain the same specimen voltage, or adjust both.

Reconstruction (not necessarily laser)

Post-upgrade parameters

How do the reconstruction parameters change after the new detector upgrade and in the presence of the laser. The K factor and the evaporation field for an element in the presence of laser.

Dan Schreiber's recon

Could Dan Schrieber’s multilayer results be explained in terms of other effects? For example, slight tilt in the layers or the tip not perpendicular to the local electrode?

Last-in, First-out recons

Would the reconstruction of multilayers benefit from a last-in/first-out reconstruction routine?

Non-hemispherical tips

Special applications


Characterizing thick oxides and their experiences with those systems. Praneet would like to learn any specific suggestions they have for oxides.


More on Tom Kelly’s presentation from the Iowa State inauguration of a LEAP tomograph--quantitative (?) or GOOD qualitative analysis of H and hydrides

New Instrumentation


How long should it take us to obtain 3x10-11 Torr with the new NEG? Have you measured the partial pressure of hydrogen in the LEAP at this total pressure?

3000 X HR

Details, including mass spectra & FOV (as compared to 3000 X Si)

Other software issues

"Extended" POS format (w/ Sydney) ?

Progress on integrated precipitate finding (replacement of envelope method)

Tip Failure

Any documentation of the various modes of tip failure and specific circumstances under which they occur. When Praneet was at Imago Roger talked about documenting the various types of tip failures.