Photon-stimulated desorption of F− ions from CF3Cl adsorbed on Si(111)-7×7

Abstract

We report the photon-stimulated desorption of negative ions induced by direct dipolar dissociation and dissociative electron attachment. The photon-stimulated desorption of F(-) ions from CF(3)Cl physisorbed on a Si(111)-7x7 surface at 30 K in the photon energy range 12-35 eV was studied. The F(-) ion yield exhibits four resonances, at 12.8, 16.2, 19.5, and 22.3 eV, quite unlike the gas phase photodissociation cross section. The intensities of these resonances depend strongly on the CF(3)Cl coverage in a manner which varies from peak to peak. The resonances at 19.5 and 22.3 eV, which have a significant enhancement in the monolayer regime, are due to electron mediated dipolar dissociation of adsorbed CF(3)Cl molecules. The enhancement is attributed to surface electron attachment following molecular excitation. A significant enhancement in the monolayer regime has also been observed for the resonances at 12.8 and 16.2 eV. These two resonances are ascribable to a combination of electron mediated dipolar dissociation and dissociative electron attachment driven by photoelectrons generated in the neighboring molecules.

Monochromatic soft-x-ray-induced reactions of CF2Cl2adsorbed on Si(111)-7 × 7 studied by continuous-time photon-stimulated desorption spectroscopy near the F(1s) edge

“…It is well known that the excitations of the core-level electrons by the tunable soft x-ray photons of synchrotron radiation (SR) can cause the site-specific chemical reactions of adsorbed species [1][2][3][4][5][6][7]. Several experiments on SR-stimulated processes [8][9][10][11][12][13][14][15] on semiconductor surfaces have been performed, and understanding the basic mechanisms responsible for the photochemical reactions of adsorbates on a semiconductor surface has become a very important research work [16][17][18][19][20][21][22][23][24][25][26][27].…”