Mechanism of state-specific enhancement in photon-stimulated desorption as studied using a polarization-dependent technique

Sekiguchi, Takuya; Baba, Yuji; Shimoyama, Iwao; Wu, Guohua; Kitajima, Yoshinori

doi:10.1016/j.susc.2005.06.076

Cited by 2 publications

(1 citation statement)

References 22 publications

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“…It was shown that excitation energy spectra of desorption ion yields are in fact dependent dramatically on incident angles in CO chemisorbed on Ru(001), pioneering how to elucidate the symmetry of double excitations. Recently, studies using the angle-dependent desorption technique have been reported for materials including multilayered molecules [4] and self-assembled monolayer molecules [5], where dominant interaction would be of inter-molecular. Only few papers, however, have been reported for monomolecular-layers, where main interaction is of adsorbate-substrate, although it is intriguing to see how desorption depends on molecular configuration on surfaces.…”

Section: Introductionmentioning

confidence: 99%

Enhancement effect in photon-stimulated ion desorption for benzene adsorbed on silicon surfaces observed using angle-dependent technique

Sekiguchi

Ikeura-Sekiguchi

Baba

2008

Applied Surface Science

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We have investigated photon-stimulated ion desorption from deuterated benzene (C 6 D 6) adsorbed on Si(100) and Si(111) surfaces following C 1s core excitation. Using time-of-flight mass spectrometry combined with angle dependent technique, we measured the dependences of mass-spectra of desorption ions on photon energies and on incident angle (θ) of synchrotron beam. We have found the ion yields for adsorbate-derived fragments of CD + and CD 2 + are enhanced in very small angles of incident x-rays. Moreover, molecular orientation effect appeared in excitation energy dependences of D + ions from the Si(100) and Si(111) surfaces; that is, ion yield spectra measured at θ=10° are different from that at θ=65°. Furthermore, it was found that desorption ion yields increase greatly with decreasing incident angles. The angular dependences are consistently similar for all ion species, excitation energies, and indexes of substrates. Possible desorption processes are described on the basis of the observations.

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Section: Introductionmentioning

confidence: 99%

Enhancement effect in photon-stimulated ion desorption for benzene adsorbed on silicon surfaces observed using angle-dependent technique

Sekiguchi

Ikeura-Sekiguchi

Baba

2008

Applied Surface Science

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Selective chemical bond breaking characteristically induced by resonant core excitation of ester compounds on a surface

Wada

Kizaki

Matsumoto

et al. 2006

J. Phys.: Condens. Matter

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Inner-shell excitation possesses an attractive potential to induce selective chemical bond breaking due to its special localization and atomic selectivity. This paper reviews our recent works about site-selective (or site-specific) photon stimulated desorption (PSD) of core-excited ester compounds, poly(methyl methacrylate) (PMMA) thin films, condensed methyl isobutyrate (MIB) multilayers, methyl ester terminated self-assembled monolayers (SAMs), partially deuterided SAMs and ethyl ester terminated SAMs. Exact selective bond breaking was observed for all molecular systems except for MIB multilayers: COO-R (R = CH 3 , C 2 H 5) breaking in the σ*(COO-R) ← C 1s, O 1s(OR) excitations and CO-OR in the σ*(CO-OR) ←O 1s(OR) excitation. Such resonant excitations take place within the functional group locally and the initial memory of the excited site and its localization character is effectively conserved during the PSD process even after subsequent Auger decays and ionic dissociation/desorption. Variation of selectivity observed here indicates the importance of the molecular environment and the contribution of the indirect dissociation process due to statistical energy relaxation and x-ray-induced electron stimulated desorption. The obvious polarization dependence measured only for selectively desorbing ions also supports the above characteristics. Neutral fragments desorbing from core-excited PMMA follow the profile of the total electron yield spectrum but not the partial ion yield of corresponding ions. This result indicates that ionic dissociation locally promoted by Coulomb repulsion plays an important role to reveal site-selectivity in chemical reactions induced by core-level excitation.

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Mechanism of state-specific enhancement in photon-stimulated desorption as studied using a polarization-dependent technique

Cited by 2 publications

References 22 publications

Enhancement effect in photon-stimulated ion desorption for benzene adsorbed on silicon surfaces observed using angle-dependent technique

Enhancement effect in photon-stimulated ion desorption for benzene adsorbed on silicon surfaces observed using angle-dependent technique

Selective chemical bond breaking characteristically induced by resonant core excitation of ester compounds on a surface

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