Thermally-induced evolution of codeposited CoSi layers on Si(100) surfaces

• Published in: Surface science Vol. 365; no. 2; pp. 403 - 410
• Main Authors: Rangelov, G., Fauster, Th
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 20.09.1996; Amsterdam Elsevier Science; New York, NY
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Low-energy electron diffraction (LEED); Metal-semiconductor interfaces; Physics; Silicides; Single-crystal epitaxy; Soft X-ray photoelectron spectroscopy; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Metal-semiconductor interfaces; Silicides; Soft X-ray photoelectron spectroscopy; Single-crystal epitaxy; Low-energy electron diffraction (LEED); Thin films; Inorganic compounds; Phase transformations; Cobalt silicides; Temperature effects; Transition element compounds; Crystallization; Experimental study; Photoelectron spectroscopy
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/0039-6028(96)00735-2

The formation of ultrathin epitaxial layers of CoSi 2 on Si(100) surfaces is studied by means of valence-band and core-level photoemission spectroscopy with synchrotron radiation, low-energy electron diffraction (LEED) and Auger electron spectroscopy. The CoSi 2 films are prepared by the template method in which an amorphous layer with CoSi 2 stoichiometry is coevaporated on top of a 2.6–3 monolayer thick Co overlayer at room temperature. The amorphous layer does not react to CoSi 2. Annealing to 300°C leads to the crystallization of the layer demonstrated by the formation of a (✓2×✓2)R45° LEED pattern. This layer consists of disilicide in CaF 2 structure with some contribution from another silicide phase. This surface is stable at least up to 460°C. After further annealing above 460°C the disilicide disappears, at least from the sub-surface layer, and the surface is covered by clean Si patches and patches of the second silicide phase. The new silicide phase is characterized by a (2✓2×✓2) R45° LEED pattern and has a different electronic structure and Si 2p binding-energy shifts. A comparison with previous experimental results and existing theoretical electronic structure calculations suggests that the new silicide phase can be identified as adamantane disilicide.