TITLE

Photodesorption from ultra-thin metal films — a comparison of SO2 and NO2 on Ag/Si(100)

AUTHOR(S)
Wesenberg, C.; Autzen, O.; Hasselbrink, E.
PUB. DATE
August 2007
SOURCE
Applied Physics A: Materials Science & Processing;Aug2007, Vol. 88 Issue 3, p559
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
The photochemistry of SO2 on thin epitaxial Ag films (5–60 nm) deposited on Si(100) has been studied using laser light with the wavelengths of 266, 355, and 532 nm. SO2 desorbs with cross sections of 1.7×10-19,1.7×10-20 and 2.9×10-21 cm2, respectively. The average translation energy, 〈Etrans/2k〉, is 440 K for 266 and 355 nm light, and 270 K for 532 nm light. Cross sections for a 60 nm thick Ag film are practically identical to the ones for Ag(111) as the substrate. An increase by a factor of ∼3.5 is observed when the film thickness is reduced to 5 nm for 266 and 355 nm light. No significant change is observed for 532 nm excitation. The film thickness has no significant influence on the translational energy of the photodesorbed molecules. The data are discussed in connection with the change of absorptivity of the metal film–semiconductor system. A model is put forward which takes into account the light absorption in the Si substrate and the reduced relaxation of excited electrons in Si. Modelling indicates that electrons excited in the Si substrate with energies and parallel momenta not allowed in Ag contribute to the surface chemistry after crossing the gap in the projected band structure of Ag(111).
ACCESSION #
25524313

 

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