Hedhili M N, Cloutier P, Bass A D, Madey T E, Sanche L
Department of Physics and Astronomy and Laboratory for Surface Modification, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854 -8019, USA.
J Chem Phys. 2006 Sep 7;125(9):094704. doi: 10.1063/1.2338030.
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- (the dominant signal) as well as S-, CH2-, SH- and SCH2-. 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- signal from electron irradiated (beam-damaged) thiophene films and the appearance of a new DEA resonance in the S- 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 C4H3S- (Thiophene-H)- 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-, S-, SH-, (Thiophene-H)-, and (Thiophene+H)- 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- and S- are observed to desorb from films of 2-2-bithiophene and no resonance is seen below approximately 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.
利用阴离子的电子激发脱附（ESD）来探究电子辐照对噻吩薄膜的影响，我们报告了电子轰击多晶铂衬底上凝聚的多层噻吩的测量结果。在22 eV以下且电子剂量较低时，解吸的阴离子包括H-（主要信号）以及S-、CH2-、SH-和SCH2-。产率函数表明，阴离子通过在9.5、11和16 eV处观察到共振的解离电子附着（DEA）以及能量>13 eV时的偶极解离（DD）而解吸。电子辐照（束损伤）噻吩薄膜的S-信号增加以及S-产率函数中在6 eV处出现新的DEA共振与噻吩环的破裂以及薄膜内硫端基产物的形成有关。环破裂的阈值能量为5 eV。从电子辐照薄膜中还观察到新阴离子如C4H3S-（噻吩-H）-的解吸，这些可能源于薄膜中合成的大辐射产物分子的分解。已退火至300 K的辐照噻吩薄膜中H-、S-、SH-、（噻吩-H）-和（噻吩+H）-阴离子的产率函数，每个都表现出以5.1 eV为中心的单个共振特征，表明所有信号都来自DEA到相同的分子辐射产物。相比之下，从2,2'-联噻吩薄膜中仅观察到H-和S-解吸，并且在阴离子产率函数中低于约10 eV时未观察到共振。这些数据表明电子辐照导致开环低聚物的形成，并且如果形成闭环或“经典”低聚物（类似于联噻吩），对阴离子的ESD贡献很小。
