Growth and thermal stability of Ag or Au films on Nb(110)
The growth and thermal stability of ultrathin (<50-A-thick) Ag and Au films on Nb(110) was investigated with use of photoemission spectroscopy and low-energy electron-diffraction (LEED) patterns. The LEED results show that Ag or Au forms a monolayer which is commensurate with the substrate, but also show that the structure of this overlayer reverts to a more close-packed structure after three monolayers (ML) have been deposited. Photoemission spectra show trends that suggest the evolution of the Ag or Au band structure with coverage and also show that a surface deposit of at least 2 ML of Ag or Au is required to observe valence-band states characteristic of the bulk metal. Further examination of the photoemission spectra suggests that the Ag or Au d-band states play only a small role in the chemical bonding that occurs between the noble metals and Nb(110), and this can be contrasted with the extensive d-band involvement in chemisorption bonds formed between Pd or Pt and Nb(110). Heating does not cause substantial change in the electric structure of 12.8-ML-thick Ag films and they thermally desorb from Nb when heated above 830 K. Similar Au films intermix with Nb to form a disordered surface phase when heated beyond 750 K. Desorption or complete in-diffusion of Au occurs when the substrate is heated beyond 1100 K. Implications for the formation of strained surface layers and surface chemical properties of noble metals on Nb(110) are discussed.
- Research Organization:
- Brookhaven National Laboratory, Upton, New York 11973-5000
- OSTI ID:
- 6927339
- Journal Information:
- Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 38:5; ISSN PRBMD
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360104* -- Metals & Alloys-- Physical Properties
CHEMICAL BONDS
COATINGS
COHERENT SCATTERING
DESORPTION
DIFFRACTION
ELECTRON DIFFRACTION
ELECTRON SPECTROSCOPY
ELECTRONIC STRUCTURE
ELEMENTS
FILMS
GOLD
GROWTH
METALS
NIOBIUM
PHOTOELECTRON SPECTROSCOPY
SCATTERING
SILVER
SPECTROSCOPY
STABILITY
SURFACES
TRANSITION ELEMENTS
VERY HIGH TEMPERATURE