Three dimensional nanoscale composition mapping of semiconductor nanowires
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Three-Dimensional Nanoscale Composition Mapping of Semiconductor Nanowires. D.E. Perea, J.E. Allen, S.J. May, B.W. Wessels, D.N. Seidman, L.J. Lauhon Nano Letters 6 (2). Feb 2006, p181-185. Joanne Yim EE C235/NSE C203. Nanowire composition.

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Three-Dimensional Nanoscale Composition Mapping of Semiconductor Nanowires

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Three dimensional nanoscale composition mapping of semiconductor nanowires

Three-Dimensional Nanoscale Composition Mapping of Semiconductor Nanowires

D.E. Perea, J.E. Allen, S.J. May, B.W. Wessels, D.N. Seidman, L.J. Lauhon

Nano Letters 6(2). Feb 2006, p181-185.

Joanne Yim

EE C235/NSE C203

EE C235/NSE C203


Nanowire composition

Nanowire composition

  • Compositional flucuations especially critical at nanoscale

    • Dopants, catalyst, at interface, etc…

  • Composition mapping tools:

    • SIMS = secondary ion mass spectroscopy: resolution limited to >100nm

    • TEM = transmission electron microscopy (Energy Dispersive X-ray Spectroscopy and Electron Energy Loss Spectroscopy): not for volumetric, low concentration.

      • Averaged over electron beam spot size

    • Cross sectional Scanning Tunneling Microscopy (XSTM)

      • Requires making a cross section

      • 2D

EE C235/NSE C203


Leap microscope

LEAP Microscope

  • Local Electrode Atom Probe microscope

  • Sub-nanometer resolution for atom tomography (imaging by sectioning)

  • Create 3D mapping of composition

  • First data published from commercial instrument in 2002

3 easy payments of

$999,999.95

(prices and participation may vary)

EE C235/NSE C203

http://www.imago.com/imago/


Three dimensional nanoscale composition mapping of semiconductor nanowires

  • microtip sample: ~100nm radius of curvature in UHV chamber

  • + bias sample, makes positive ions on sample tip

    • negatively pulsed local electrode tip to induce positive ions to leave

  • Position sensitive detector collects ions

    • Lighter mass -> travel faster

    • Mass-to-charge -> element

    • Relative composition using counts

    • Straight line travel -> relative positions

EE C235/NSE C203

http://www.imago.com/imago/html/technology/technology.jsp


Experimental

Experimental

  • Au seed-catalyzed InAs nanowire growth on GaAs(111)B by MOVPE

    • Epitaxial, vertical array of nanowires 140um long, spaced 500um apart as defined by initial Au e-beam/liftoff

EE C235/NSE C203


Three dimensional nanoscale composition mapping of semiconductor nanowires

SEM

(curvature is software artifact)

Cross section shows lines corresponding to growth planes (0001) â”´ growth direction

spacing of 0.35nm

Au atoms

(98% In, As removed for picture)

EE C235/NSE C203


Three dimensional nanoscale composition mapping of semiconductor nanowires

Catalyst-nanowire interface

23x14x14 nm3

10 nm dia X 1 nm thick slices

Interface width <0.5nm

www.nsf.gov/mps/dmr/highlights/05highlights/imr/0449933.ppt

EE C235/NSE C203


Summary

Summary

  • 3D composition mapping can be achieved

  • LEAP microscope sample geometry ideal for nanowire morphology

  • Found Au catalyst incorporated along length of nanowire

EE C235/NSE C203


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