Details

Autor(en) / Beteiligte

• Würz, R.
• Bohne, W.
• Fuhs, W.
• Röhrich, J.
• Schmidt, M.
• Schöpke, A.
• Selle, B.

Titel

Composition and Structure of Epitaxial CaF2 Layers at the First Stages of Their Growth on Si(111)

Ist Teil von

• MRS proceedings, 2001, Vol.696

Ort / Verlag

New York, USA: Cambridge University Press

Erscheinungsjahr

2001

Beschreibungen/Notizen

• CaF2 films with thicknesses in the monolayer range (<20 Å) were grown on Si(111) by evaporation from a CaF2 source at UHV conditions. They were characterized ex-situ by Heavy-Ion Elastic Recoil Detection Analysis (HI-ERDA), RBS/Channeling, X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM). The F/Ca ratio of the films was found to depend on the growth temperature Ts and to deviate appreciably from the stoichiometric composition (F/Ca=2). Due to an interface reaction which leads to a CaF-interface layer a change from polycrystalline to epitaxial growth occurs at Ts=450°C. At higher temperature film growth started with a closed layer of CaF on top of which CaF2 layers with an increasing fraction of pinholes were formed. By means of a two-step process at different temperatures, the amount of pinholes could be strongly reduced. It was found, that buffer layers of CaF2 with a CaF interface layer introduced in Au/p-Si contacts enhance the barrier height by as much as 0.36eV to values of 0.64eV.