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Substantially Transparent Pt, Pd, Rh, And Re Films: Preparation and Properties

Published online by Cambridge University Press:  28 February 2011

D. E. Aspnes  and
A. Heller
D. E. Aspnes
Affiliation:
Bellcore, Red Bank, N.J. 07701-7020
A. Heller
Affiliation:
AT&T Bell Laboratories, Murray Hill, N.J. 07974
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Abstract

Films of Pt, Pd, Rh, and Re with metal volume fractions of 0.3 to 0.5 have been prepared by mass-transport-limited photoelectrodeposition onto (001) p-InP photocathodes from ∼5 × 10−5 M solutions of the metal ions in 1 M HClO4. These films exhibit their normal catalytic activities (e.g., in hydrogen evolution) and have normal crystal structures, yet are substantially more transparent than equivalent dense films of the same metal loading per unit area. Effective-medium analysis of the spectroellipsometrically measured dielectric functions of these films shows that the anomalous transparency is due to microstructure: depolarization factors and metal packing fractions obtained by best-fit model calculations indicate dendritic (Rh), particulate (Pt, Pd), or platelet (Re) forms that are poorly interconnected in directions parallel to the surface, and whose dimensions are all small compared to the wavelength of light. Transmission electron micrographs confirm these results and reveal that these films consist of primary building blocks of ca. 5 nm crystallites that are organized into relatively loosely packed secondary structures. Potential applications of these films include the formation of efficient metallic-catalyst-coated photoelectrodes on poor-quality semiconductors.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 111: Symposium O – Microstructure and Properties of Catalysts , 1987 , 379
Copyright
Copyright © Materials Research Society 1988

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References

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