Surface-Reconstruction-Induced Changes in Free-Carrier Scattering from the W(100) Surface: AnInfrared Surface-Electromagnetic-Wave Study

Authors

D. Mark Riffe, Utah State UniversityFollow
L. M. Hanssen
A. J. Sievers

Document Type

Article

Journal/Book Title/Conference

Physical Review B

Volume

34

Issue

2

Publication Date

7-15-1986

First Page

692

Last Page

703

Abstract

Using the infrared-absorption technique of surface-electromagnetic-wave spectroscopy (SEWS) we have studied the effects of H₂ and D₂ chemisorption on the SEW attenuation coefficient α in the 10-μm region between 165 and 350 K. The change in α at room temperature has also been measured for N₂, O₂, and CO adsorption. The coverage (CTHETA) dependence of α for N₂, O₂, and CO is fairly simple [either a monotonic increase (N₂) or a peak at some intermediate coverage (O₂, CO)] and points to changes in free-carrier (FC) surface scattering as the dominant α-changing mechanism. Much richer structure in α(CTHETA) upon H₂ and D₂ adsorption is observed: A small peak followed by a sharp dip at CTHETA=0.42 monolayer (ML) (CTHETA=2 monolayers ≡saturation), a broad maximum at CTHETA=1.28 ML, and a value at CTHETA=2.0 ML higher than for the clean surface. For CTHETA>0.42 ML the variations are dominated by reconstruction-induced changes in FC scattering from the surface. The difference in α between CTHETA=1.28 ML and saturation indicates that the CTHETA=1.28 ML disordered surface phase and the CTHETA=2.0 ML p(1×1)-D phase are temperature independent between 165 and 300 K. Adsorbate-induced quenching of the W(100) 0.3-eV intrinsic surface states also contributes to the changes in α; the associated loss of oscillator strength is most apparent in a strong frequency dependence of α relative to the clean surface for D₂ adsorption. In addition, it is possible that a decrease in relaxation of the W(100) surface as CTHETA approaches 0.42 ML for H₂ or D₂ has some effect on the SEW attenuation by influencing the amount of FC interband scattering at the metal-vacuum interface.

Comments

Published by American Physical Society in Physical Review B. Publisher PDF is available for download through link above.

Recommended Citation

"Surface-Reconstruction-Induced Changes in Free-Carrier Scattering from the W(100) Surface: An Infrared Surface-Electromagnetic-Wave Study," D. M. Riffe, L. M. Hanssen, and A. J. Sievers, Phys. Rev. B 34, 692 (1986).