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Characterization of coumarin-6 polycrystalline films growth from vacuum deposition at various substrate temperatures
Coumarin-6 polycrystalline films were fabricated from vacuum deposition at various substrate temperatures T(sub) from 106 to 178 °C with a fixed source temperature of 185 °C. Because of its slenderer and more asymmetric structure, the adhered coumarin-6 molecule on top of the growing interface encou...
Autores principales: | , , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Nature Publishing Group UK
2018
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6233150/ https://www.ncbi.nlm.nih.gov/pubmed/30425267 http://dx.doi.org/10.1038/s41598-018-34813-w |
Sumario: | Coumarin-6 polycrystalline films were fabricated from vacuum deposition at various substrate temperatures T(sub) from 106 to 178 °C with a fixed source temperature of 185 °C. Because of its slenderer and more asymmetric structure, the adhered coumarin-6 molecule on top of the growing interface encounters a larger steric energetic barrier of 0.92 eV as estimated from the Arrhenius plot of growth rate versus 1/T(sub). From top-view SEM pictures, the as-deposited coumarin-6 thin films exhibit a twisted pattern and a kinematic roughness for T(sub) < 150 °C; while clear facets emerge for T(sub) ≥ 150 °C due to the increase of surface diffusion energy of the adhered molecules. From XRD analysis, besides the confirmation of the triclinic structure two anomalous peaks observed at 2θ ~ 9.007° and 7.260° are explained due to the co-existence of N- and S-coumarin-6-isomers within the crystalline grains. Furthermore, for coumarin-6 polycrystalline films deposited at T(sub) = 150 °C with high crystallinity of the constituent grains, the bandgap determined from optical transmission is around 2.392 eV; and from photoluminescence spectra, the fitted four emission components are assigned to the Frenkel and charge transfer excitons recombination with participation of molecular vibrational states. |
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