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Atom probe tomography

 

Among only a few other groups throughout the world, we apply atom probe tomography to obtain a chemical analysis in outstanding spatial resolution. This extraordinary technique delivers real three-dimensional pictures of the specimen in atomic resolution. Individual atoms of the specimen are field evaporated by short high voltage pulses, up to 5000 Volts, or by assistance of laser pulses. The evaporated atoms are accelerated towards a detector that records flight time and impact position. Based on these data the chemical identity of the atom and its original position inside the analysed volume is numerically reconstructed with the accuracy of a few Angstroem. A typical measurement contains up to the order of 10 million atoms which allows to represent a complete volume.

Specimen preparation

Atom probe tomography requires tip-shaped specimens with a curvature radius at the apex ranging from 20 to 50 nm. The production of these specimens is not science but art! Depending on material we use electropolishing or ion-etching. In difficult cases, e.g multilayers or semi-conducting materials, we also apply lithography and focussed ion beams (Dual Beam FIB). Our speciality is the direct deposition of thin films on pre-developed substrate tips. In former times atom probe tomography was limited to metallic samples. Recently, this restriction has been overcome by the introduction of laser-assisted evaporation. Even semi-conducting or insulating materials, directly cut out of the structure of a microchip, could be already analysed with atom probe tomography.
Tap PrinzipTap Alcual

 

Instruments in operation

According to our specifications, we are operating self-designed instruments,
produced in outstanding quality by our workshop.

  • Laser-assisted wide angle 3D-atomprobe equiped with a micro-extraction electrode
    Flight path: 130 mm, Delay line detector 70 mm Ø, tip voltage: 16kV
    Laserpuls: 10 μJ, 200kHz, Pulsbreite 250 ps
  • wide angle 3D-atomprobe
    Flight path: 150 mm, Delay line detector 120 mm Ø, tip voltage: 16 kV
    electric pulse: 5 kV, 25 kHz, pulse width 7 ns
    laser pulse: 15 μJ, 1500 Hz, pulse width 500 ps
  • Field ion microscope to prepare and characterise tip-shaped substrates
    tip voltage: 16 kV, numerical aperture: ± 45°
  • Dedicated deposition chamber for tip coating
    ion beam sputter deposition, Kaufmann ion source

You are interested in obtainig an analysis or a cooperation? Just write an  e-mail.


literature

G.Schmitz: 'Nanoanalysis by atom probe tomography', H. Fuchs (ed.) 'Nanotechnology' (Volume 6) Wiley-VCH, Weinheim 2009

Tien T. TSONG: Atom-Probe Field Ion Microscopy (Campridge University Press, 2005)

M. K. Miller: Atom Probe Tomography (Kluwer Academic/Plenum Publishers, 2000)

M.K. Miller, G.D.W. Smith: Atom Probe Microanalysis (Materials Research Society, 1989)


Imprint | © 2012 Institute of Materials Physics
AG Schmitz Institute of Materials Physics
Wilhelm-Klemm-Straße 10
· 48149 Münster
Tel.: 0251 83-33572 · Fax: 0251 83-38346
E-Mail: gschmitz@uni-muenster.de