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Title: Strain and stability of ultrathin Ge layers in Si/Ge/Si axial heterojunction nanowires

The abrupt heterointerfaces in the Si/Ge materials system presents useful possibilities for electronic device engineering because the band structure can be affected by strain induced by the lattice mismatch. In planar layers, heterointerfaces with abrupt composition changes are difficult to realize without introducing misfit dislocations. However, in catalytically grown nanowires, abrupt heterointerfaces can be fabricated by appropriate choice of the catalyst. Here we grow nanowires containing Si/Ge and Si/Ge/Si structures respectively with sub-1nm thick Ge "quantum wells" and we measure the interfacial strain fields using geometric phase analysis. Narrow Ge layers show radial strains of several percent, with a corresponding dilation in the axial direction. Si/Ge interfaces show lattice rotation and curvature of the lattice planes. We conclude that high strains can be achieved, compared to what is possible in planar layers. In addition, we study the stability of these heterostructures under heating and electron beam irradiation. The strain and composition gradients are supposed to the cause of the instability for interdiffusion.
 [1] ;  [2] ;  [3] ;  [1] ;  [2]
  1. IBM, Yorktown Heights, NY (United States). Thomas J. Watson Research Center
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
  3. National Taiwan Univ., Taipei (Taiwan)
Publication Date:
OSTI Identifier:
Report Number(s):
BNL-108075-2015-JA; BNL-108172-2015-JA
Journal ID: ISSN 1530-6984; KC0403020
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 15; Journal Issue: 3; Journal ID: ISSN 1530-6984
American Chemical Society
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
36 MATERIALS SCIENCE; nanowires; in situ growth; heterostructures; functional nanomaterials; nanowire heterostructures; silicon; germanium; abrupt interfaces; strain distribution; structural instability