1 September 1991 Formation and electronic properties of epitaxial erbium silicide
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Rare-earth silicides form very low Schottky barriers on n-type Si ( 0,3 eV) and have good electrical and thermal conductivity. They are attractive for applications in JR detectors or as ohmic contacts on Si. We have studied, by surface techniques (LEED, XPS, UPS and AES), the formation and the electronic properties of erbium silicide thin films epitaxially grown on Si(1 1 1) substrates. Erbium was evaporated under ultra-high vacuum on clean Si(1 1 1) (7x7) surfaces and several methods of solid phase epitaxy were used. Jt was found that the "template" method, successive cycles of deposition of 20 A Er - 25 A Si double layer followed by annealing gave the best film morphology. The silicide composition (1 Er : ' 1.7 Si) was attained after annealing of the deposits at 560- 600° C. The crystalline quality of the films improved upon annealing at higher temperature and sharp LEED spots were obtained at 800 - 900° C. The chemical shifts of the Si and Er XPS core-levels were very weak, , - 0.4 eV for Si 2p and negligible for Er 4d, indicating a weak charge transfer and metallic bonding. The valence band of epitaxial (0001) ErSil.7, formed by hybridized Er sd - Si sp states, spread from E to '-' - 4.5 eV, leaving the Er 4f states unaffected. Angle resolved UPS revealed great energy E (k) dispersion in the surface plane but undetectable energy dispersion along the perpendicular to the surface, suggesting a 2 D character of the siicide films.
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Tan T.A. Nguyen, J. Y. Veuillen, "Formation and electronic properties of epitaxial erbium silicide", Proc. SPIE 1512, Infrared and Optoelectronic Materials and Devices, (1 September 1991); doi: 10.1117/12.47172; https://doi.org/10.1117/12.47172

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