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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

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/

slide4

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

slide6

SEM

(curvature is software artifact)

Cross section shows lines corresponding to growth planes (0001) ┴ growth direction

spacing of 0.35nm

Au atoms

(98% In, As removed for picture)

EE C235/NSE C203

slide7

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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