Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 24: Postersitzung (Epitaxie und Wachstum, Oxide und Isolatoren, Elektronische Struktur, Oberfl
ächenreaktionen, Adsorption an Oberfl
ächen, Organische Dünnschichten)

O 24.3: Poster

Mittwoch, 26. März 2003, 14:30–17:30, P1

High temperature growth of CaF₂ on Si(111) substrates — •C.R. Wang¹, B.H. Müller¹, K.R. Hofmann¹, M. Bierkandt², C. Deiter², and J. Wollschläger² — ¹Inst. für Halbleiterbauelemente und Werkstoffe, Appelstr 11a, 30167 Hannover — ²Inst. für Festkörperphysik, Appelstr. 2, 30167 Hannover

The initial stages of high temperature (700^∘C) growth of CaF₂ on Si(111) substrates have been studied by ex-vacuo atomic force microscopy. At these temperatures, CaF₂ molecules react with the silicon surface and form a CaF₁-Si interface layer, which completely covers the surface before CaF₂ starts to grow. Using the material contrast ability of lateral force microscopy (LFM) a direct distinction between the CaF₁-Si interface layer and CaF₂ can be achieved. Furthermore, the LFM signal shows a contrast between CaF₂ and two types of CaF₁. The CaF₁ phase with the highest friction appears rough in AFM topography, while the other is smooth. Also thicker CaF₂ films grown at 700^∘C show largely disordered areas as well as smooth regions. We speculate that the disturbed regions evolve from the rough CaF₁ surface fraction. To explain the existence of two different CaF₂ types, we will present an explanation approach which involves the thermal decomposition of calcium fluoride.