Visualization of molecular packing and tilting domains and interface effects in tetracene thin films on H/Si(001)

Tersigni, Andrew; Sadowski, Jerzy; Qin, X. R.

doi:10.1002/pssb.201600777

Cited by 2 publications

(3 citation statements)

References 39 publications

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“…This argument is further supported by calculating the angledependent NEXAFS C K-edge spectra for the published XRDderived crystal structures of bulk (Tc I). 34 For comparison, the corresponding spectrum of thin-film Tc (Tc II) 20 is also shown. The calculated spectrum, especially for Tc I, is now in very good agreement with the experiment.…”

Section: ■ Resultsmentioning

confidence: 99%

“…However, from NEXAFS alone it is not clear if the molecules are oriented with the molecular long axis (LA) closer to be parallel to the underlying surface or perpendicular to it (see Figure 4). From all reports in the literature (utilizing XRD, LEED, and AFM) 9,10,17,19,20,23,24,26 as well as our own total energy calculations, we can safely assume an uprightstanding Tc orientation.…”

Section: ■ Comparative Discussionmentioning

confidence: 99%

“…Tc structure formation has been widely studied on several different weakly interacting surfaces, including H–Si, ,,− Si oxide, ,,− AlO x /Ni 3 Al(111), − polystyrene, parylene C, poly(methyl methacrylate), hexamethyldisilazane, Mylar, evaporated carbon, and highly oriented pyrolytic graphite . Thanks to the weak coupling to the substrates, the results are largely transferable.…”

Section: Introductionmentioning

confidence: 99%

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Tetracene Ultrathin Film Growth on Hydrogen-Passivated Silicon

et al. 2020

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Inorganic−organic interfaces are important for enhancing the power conversion efficiency of silicon-based solar cells through singlet exciton fission (SF). We elucidated the structure of the first monolayers of tetracene (Tc), an SF molecule, on hydrogen-passivated Si( 111) ] and hydrogenated amorphous Si (a-Si:H) by combining near-edge X-ray absorption fine structure (NEXAFS) and Xray photoelectron spectroscopy (XPS) experiments with density functional theory (DFT) calculations. For samples grown at or below substrate temperatures of 265 K, the resulting ultrathin Tc films are dominated by almost upright-standing molecules. The molecular arrangement is very similar to the Tc bulk phase, with only a slightly higher average angle between the conjugated molecular plane normal and the surface normal (α) around 77°. Judging from carbon K-edge X-ray absorption spectra, the orientation of the Tc molecules are almost identical when grown on H−Si(111) and a-Si:H substrates as well as for (sub)mono-to several-monolayer coverages. Annealing to room temperature, however, changes the film structure toward a smaller α of about 63°. A detailed DFT-assisted analysis suggests that this structural transition is correlated with a lower packing density and requires a well-chosen amount of thermal energy. Therefore, we attribute the resulting structure to a distinct monolayer configuration that features less inclined, but still well-ordered molecules. The larger overlap with the substrate wave functions makes this arrangement attractive for an optimized interfacial electron transfer in SF-assisted silicon solar cells.

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Section: ■ Resultsmentioning

confidence: 99%

Section: ■ Comparative Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Tetracene Ultrathin Film Growth on Hydrogen-Passivated Silicon

et al. 2020

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Coverage-dependent crystalline domain structures of a tetracene thin film on H/Si(001)

Tersigni

Qin

2019

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Atomic force microscopy, transverse shear microscopy, and friction force microscopy have been used to study coverage-dependent crystalline domain structures of a tetracene film on a hydrogen-passivated Si (001)-2 × 1 surface. Though submonolayer fractals present some nonepitaxial domains, the coalesced first monolayer, which possesses a partial commensurate registration with the substrate lattice, shows two lattice domains (major domains) orthogonally oriented with each other. The second-layer lattice exhibits 90° azimuthal rotation from the first-layer lattice, and the third and subsequent layers show a commensurate registration with their respective underlayers. The major-domain boundaries are not the preferable nucleation sites, indicating a potential energy barrier at the boundary. Meanwhile, the domain structure rigidity increases with the layer height until it saturates on the fourth layer, where the bulklike structure emerges with the formation of two (molecular tilting) subdomains in a major domain. The authors conclude that the structural-phase transition can take place locally wherever the fourth molecular layer emerges, and significant bulklike crystallization occurs at a nominal coverage of ∼3–4 ML.

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Visualization of molecular packing and tilting domains and interface effects in tetracene thin films on H/Si(001)

Cited by 2 publications

References 39 publications

Tetracene Ultrathin Film Growth on Hydrogen-Passivated Silicon

Tetracene Ultrathin Film Growth on Hydrogen-Passivated Silicon

Coverage-dependent crystalline domain structures of a tetracene thin film on H/Si(001)

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