Photoemission investigation of bulk-grown versus epitaxial thin film CoSi2(111) surfaces

doi:10.1016/0169-4332(92)90279-7

Applied Surface Science

Volumes 56–58, Part 1, 1992, Pages 507-513

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Abstract

We compare the valence band photoemission signatures of the CoSi₂(111) surfaces observed on a bulk-grown single crystal and on thin films epitaxially grown on Si(111). Taking advantage of the characteristic surface states in the 2.60–3.00 eV binding energy range at λ allows us to identify unambiguously the various surface structtures observed on epitaxial films obtained with different preparation methods: a Co-rich low-temperature form labeled CoSi₂(111)-Co, an intermediate surface termination labeled CoSi₂(111) and stable up to 420°C and a high-temperature Si bilayer terminated form observed upon annealing above 550°C and labeled CoSi₂(111)-Si. We find that bulk-grown single-crystal surfaces prepared by ion etching and annealing up to temperatures as high as 900°C invariably show the surface electronic structure corresponding to the intermediate surface termination labeled CoSi₂(111). This surface corresponds to the ideal crystal termination with a Si single bond CoSi silicide top layer. This surface atomic structure, is confirmed by high-resolution Si(2p) core level photoemission measurements. We show that the spectrum displays only one surface component shifted by 0.60 eV towards lower binding energies in contrast with CoSi₂(111)-Si which shows three surface components. Finally, we find that the CoSi₂(111)-Si surface can also be prepared on a bulk-grown CoSi₂ crystal by appropriate annealing of ultrathin Si deposits.

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Photoemission investigation of bulk-grown versus epitaxial thin film CoSi2(111) surfaces

Abstract

Thin Solid Films

Appl. Surf. Sci.

Appl. Phys. Lett.

Electron. Lett.

Phys. Rev. B

Phys. Rev. B

Phys. Rev. B

Appl. Surf. Sci

Photoemission investigation of bulk-grown versus epitaxial thin film CoSi₂(111) surfaces