Electron stimulated desorption of anionic fragments from films of pure and electron-irradiated thiophene
- Department of Physics and Astronomy and Laboratory for Surface Modification, Rutgers, State University of New Jersey, Piscataway, New Jersey 08854 -8019 (United States)
The electron stimulated desorption (ESD) of anions is used to explore the effects of electron irradiation on a thiophene film and we report measurements for electron impact on multilayer thiophene condensed on a polycrystalline platinum substrate. Below 22 eV and at low electron dose, desorbed anions include H{sup -} (the dominant signal) as well as S{sup -}, CH{sub 2}{sup -}, SH{sup -} and SCH{sub 2}{sup -}. Yield functions show that anions are desorbed both by dissociative electron attachment (DEA) with resonances observed at 9.5, 11, and 16 eV, and for energies >13 eV, by dipolar dissociation (DD). An increase in the S{sup -} signal from electron irradiated (beam-damaged) thiophene films and the appearance of a new DEA resonance in the S{sup -} yield function at 6 eV are linked to rupture of the thiophene ring and the formation of sulfur-terminated products within the film. The threshold energy for ring rupture is 5 eV. The desorption of new anions such as C{sub 4}H{sub 3}S{sup -} (Thiophene-H){sup -}is also observed from electron irradiated films and these likely arise from the decomposition of large radiation product molecules synthesized in the film. The yield functions of H{sup -}, S{sup -}, SH{sup -}, (Thiophene-H){sup -}, and (Thiophene+H){sup -} anions from irradiated thiophene films that have been annealed to 300 K, each exhibit a single resonant feature centered around 5.1 eV, suggesting that all signals derive from DEA to the same molecular radiation product. In contrast, only H{sup -} and S{sup -} are observed to desorb from films of 2-2-bithiophene and no resonance is seen below {approx}10 eV in the anion yield functions. These data suggest that electron irradiation causes formation of ring-opened oligomers, and that closed-ring or 'classical' oligomers, (similar to bithiophene) if formed, contribute little to the ESD of anions.
- OSTI ID:
- 20864290
- Journal Information:
- Journal of Chemical Physics, Vol. 125, Issue 9; Other Information: DOI: 10.1063/1.2338030; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
ANNEALING
DECOMPOSITION
DESORPTION
DISSOCIATION
ELECTRON ATTACHMENT
ELECTRON BEAMS
ELECTRONS
EV RANGE 01-10
EV RANGE 10-100
HYDROGEN IONS 1 MINUS
IRRADIATION
PLATINUM
POLYCRYSTALS
SULFUR IONS
TEMPERATURE RANGE 0273-0400 K
THIN FILMS
THIOPHENE