Epitaxial two dimensional aluminum films on silicon (111) by ultra-fast thermal deposition
- Department of Materials and Interfaces, Weizmann Institute of Science, POB 26, Rehovot 76100 (Israel)
- Department of Chemical Research Support, Weizmann Institute of Science, POB 26, Rehovot 76100 (Israel)
- Department of Chemical Physics, Weizmann Institute of Science, POB 26, Rehovot 76100 (Israel)
Aluminum thin films are known for their extremely rough surface, which is detrimental for applications such as molecular electronics and photonics, where protrusions cause electrical shorts or strong scattering. We achieved atomically flat Al films using a highly non-equilibrium approach. Ultra-fast thermal deposition (UFTD), at rates >10 nm/s, yields RMS roughness of 0.4 to 0.8 nm for 30-50 nm thick Al films on variety of substrates. For UFTD on Si(111) substrates, the top surface follows closely the substrate topography (etch pits), indicating a 2D, layer-by-layer growth. The Al film is a mixture of (100) and (111) grains, where the latter are commensurate with the in-plane orientation of the underlying Si (epitaxy). We show the use of these ultra-smooth Al films for highly reproducible charge-transport measurements across a monolayer of alkyl phosphonic acid as well as for plasmonics applications by directly patterning them by focused ion beam to form a long-range ordered array of holes. UFTD is a one-step process, with no need for annealing, peeling, or primer layers. It is conceptually opposite to high quality deposition methods, such as MBE or ALD, which are slow and near-equilibrium processes. For Al, though, we find that limited diffusion length (and good wetting) is critical for achieving ultra-smooth thin films.
- OSTI ID:
- 22089253
- Journal Information:
- Journal of Applied Physics, Vol. 111, Issue 12; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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