AVS 53rd International Symposium
    Nanometer-scale Science and Technology Friday Sessions
       Session NS-FrM

Paper NS-FrM2
Double-Sided Epitaxy on Si Nanowire Ribbons*

Friday, November 17, 2006, 8:20 am, Room 2016

Session: Nanowires
Presenter: C.S. Ritz, University of Wisconsin, Madison
Authors: C.S. Ritz, University of Wisconsin, Madison
F.S. Flack, University of Wisconsin, Madison
Y. Zhang, University of Utah
F. Liu, University of Utah
M.G. Lagally, University of Wisconsin, Madison
Correspondent: Click to Email
We study the ultrahigh-vacuum chemical vapor deposition growth of SiGe and Ge 3D islands on free-standing compliant Si nanowire ribbons. The Si template layer of a Si-on-insulator (SOI) sample with a thick buried oxide (BOX) is thinned down to the order of 20 nm via thermal oxidation and HF etching. This thin template layer can then be patterned into nanowire ribbons with widths less than 100nm along different crystallographic directions and connected at both ends. Reactive ion etching is used to remove the unwanted Si down to the BOX. Prior to SiGe growth a final HF dip is used to etch away this exposed oxide and undercut the Si ribbons, leaving them freestanding. CVD allows us to grow 3D islands on both the top and bottom surfaces of the Si ribbon.@footnote 1@ We observe a strong anticorrelation between islands grown on the top and bottom of the freestanding regions, as well as ordering of islands into rows along the ribbon edges. This latter ordering also exhibits additional dependence on the crystallographic orientation of the edge. Modeling suggests that this anticorrelation takes place to minimize the total strain energy and that growth on thinner ribbons induces and enhances correlation. In addition to the ordering of the dots, we also see global bending of the Si nanoribbon (because it is connected at both ends like a bridge) due to the elastic strain induced by the 3D islands. The islands affect the local electronic structure of the wire, which in concert with the ordering, makes double-sided epitaxy on nanowire ribbons a new approach to creating superlattice nanowires. @FootnoteText@ *Supported by DOE.@footnote 1@Clark S. Ritz, Frank S. Flack, Michelle M. Roberts, Donald E. Savage, Yu Zhang, Feng Liu, Max G. Lagally, Double-sided growth of ordered SiGe islands on ultra-thin Si, in preparation.