Comparison of the top-down and bottom-up approach to fabricate nanowire-based Silicon/Germanium heterostructures

A. Wolfsteller, N. Geyer, T. K. Nguyen-Duc, P. Das Kanungo, N. D. Zakharov, M. Reiche, W. Erfurth, H. Blumtritt, S. Kalem, P. Werner, U. Gösele

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)

Abstract

Silicon nanowires (NWs) and vertical nanowire-based Si/Ge heterostructures are expected to be building blocks for future devices, e.g. field-effect transistors or thermoelectric elements. In principle two approaches can be applied to synthesise these NWs: the 'bottom-up' and the 'top-down' approach. The most common method for the former is the vapour-liquid-solid (VLS) mechanism which can also be applied to grow NWs by molecular beam epitaxy (MBE). Although MBE allows a precise growth control under highly reproducible conditions, the general nature of the growth process via a eutectic droplet prevents the synthesis of heterostructures with sharp interfaces and high Ge concentrations. We compare the VLS NW growth with two different top-down methods: The first is a combination of colloidal lithography and metal-assisted wet chemical etching, which is an inexpensive and fast method and results in large arrays of homogenous Si NWs with adjustable diameters down to 50 nm. The second top-down method combines the growth of Si/Ge superlattices by MBE with electron beam lithography and reactive ion etching. Again, large and homogeneous arrays of NWs were created, this time with a diameter of 40 nm and the Si/Ge superlattice inside.

Original languageEnglish
Pages (from-to)2555-2561
Number of pages7
JournalThin Solid Films
Volume518
Issue number9
DOIs
Publication statusPublished - 26 Feb 2010
Externally publishedYes

Keywords

  • Electron beam lithography
  • Molecular beam epitaxy
  • Reactive ion etching
  • Si/Ge heterostructures
  • Silicon nanowires
  • Wet chemical etching

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