Thermally‐activated post‐growth dewetting of fullerene C<sub>60</sub> on mica

Bommel, Sebastian; Spranger, Holger; Weber, Cora; Kleppmann, Nicola; Roth, Stephan V.; Klapp, Sabine H. L.; Kowarik, Stefan

doi:10.1002/pssr.201510258

Cited by 8 publications

(7 citation statements)

References 35 publications

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“…In contrast to CuPc, the post-growth roughness of C60 thin films increases when the substrate is heated during growth. It was shown that C60 molecules react to substrate heating by island formation due to a molecular upward diffusion 95 , which explains the enhanced roughness at 400 K found in the present study. This effect is well reproduced by the simulation, see Fig.…”

Section: C60supporting

confidence: 68%

“…The random orientation of C60 crystals on native silicon oxide and the formation of islands at a very early stage of growth (as it will be discussed in Sec. IV) is in contrast to the growth of C60 on mica 94,95 . It seems that the molecule-substrate interaction plays a crucial role in thin film growth and was therefore considered as one of the main parameters in the simulations.…”

Section: Experimental Evidence Of Phase Separationmentioning

confidence: 87%

“…Previous studies investigated the evolution of roughness by recording the reflected X-ray intensities at specific q z -values during the growth of pure films. Those q z -values are the anti-Bragg point 1 / 2 •q Bragg and 2 / 3 , 3 / 4 , 4 / 5 and 5 / 6 of q Bragg 68, [90][91][92][93][94][95][96] . Due to the absence of a clear Bragg peak in the XRR-scans of pure C60 and the blended thin films there are no anti-Bragg points to be observed.…”

Section: Real-time Xrrmentioning

confidence: 99%

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Thin Film Growth of Phase-Separating Phthalocyanine-Fullerene Blends: A Combined Experimental and Computational Study

Reisz,

Empting,

Zwadlo

et al. 2021

Preprint

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Blended organic thin films have been studied during the last decades due to their applicability in organic solar cells. Although their optical and electronic features have been examined intensively, there is still lack of detailed knowledge about their growth processes and resulting morphologies, which play a key role for the efficiency of optoelectronic devices such as organic solar cells. In this study, pure and blended thin films of copper phthalocyanine (CuPc) and the Buckminster fullerene (C60) were grown by vacuum deposition onto a native silicon oxide substrate at two different substrate temperatures, 310 K and 400 K.The evolution of roughness was followed by in-situ real-time X-ray reflectivity. Crystal orientation, island densities and morphology were examined after the growth by X-ray diffraction experiments and microscopy techniques. The formation of a smooth wetting layer followed by rapid roughening was found in pure CuPc thin films, whereas C60 shows a fast formation of distinct islands at a very early stage of growth. The growth of needle-like CuPc crystals loosing their alignment with the substrate was identified in co-deposited thin films. Furthermore, the data demonstrates that structural features become larger and more pronounced and that the island density decreases by a factor of four when going from 310 K to 400 K. Finally, the key parameters roughness and island density were well reproduced on a smaller scale by kinetic Monte-Carlo simulations of a generic, binary lattice model with simple nearestneighbor interaction energies. A weak molecule-substrate interaction caused a fast island formation and a weak interaction between molecules of different species was able to reproduce the observed phase separation. The introduction of different same-species and cross-species Ehrlich-Schwöbel barriers for inter-layer hopping was necessary to reproduce the roughness evolution in the blend and showed the growth of CuPc crystals on top of the thin film in agreement with the experiment.

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Section: C60supporting

confidence: 68%

Section: Experimental Evidence Of Phase Separationmentioning

confidence: 87%

Section: Real-time Xrrmentioning

confidence: 99%

See 1 more Smart Citation

Thin Film Growth of Phase-Separating Phthalocyanine-Fullerene Blends: A Combined Experimental and Computational Study

Reisz,

Empting,

Zwadlo

et al. 2021

Preprint

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“…Studies on other molecules such as buckminsterfullerene, C 60 , report the opposite behavior of film roughening during growth on heated substrates (Bommel et al, 2015), which could be due to different molecular shapes and interaction energies. The spherical shape of C 60 molecules does not support a special growth direction.…”

Section: Discussionmentioning

confidence: 99%

Polymorphism and structure formation in copper phthalocyanine thin films

et al. 2021

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Many polymorphic crystal structures of copper phthalocyanine (CuPc) have been reported over the past few decades, but despite its manifold applicability, the structure of the frequently mentioned α polymorph remained unclear. The base-centered unit cell (space group C2/c) suggested in 1966 was ruled out in 2003 and was replaced by a primitive triclinic unit cell (space group P 1). This study proves unequivocally that both α structures coexist in vacuum-deposited CuPc thin films on native silicon oxide by reciprocal space mapping using synchrotron radiation in grazing incidence. The unit-cell parameters and the space group were determined by kinematic scattering theory and provide possible molecular arrangements within the unit cell of the C2/c structure by excluded-volume considerations. In situ X-ray diffraction experiments and ex situ atomic force microscopy complement the experimental data further and provide insight into the formation of a smooth thin film by a temperature-driven downward diffusion of CuPc molecules during growth.

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“…This journal is © the Owner Societies 2016 model step-edge effects in anisotropic (multilayer) growth morphologies on experimental scales. [67][68][69]…”

mentioning

confidence: 99%

Characterization of step-edge barrier crossing of para-sexiphenyl on the ZnO (101̄0) surface

Pałczynski

Herrmann

Heimel

et al. 2016

Phys. Chem. Chem. Phys.

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Mass transport processes of conjugated organic molecules (COMs) on inorganic surfaces are essential elements in thin film deposition for hybrid optoelectronic devices. Defects and in particular surface step-edges dictate the molecular nucleation and growth morphology, which itself determine many physical properties of the resulting hybrid interface. Here, we explore the detailed molecular kinetics and transport rates of a single physisorbed para-sexiphenyl (p-6P) molecule crossing a step-edge (a "hetero-Ehrlich-Schwoebel barrier") on the inorganic ZnO (101[combining macron]0) surface by a combination of all-atom molecular dynamics simulations and passage time theory. We determine temperature- and charge-dependent (free) energy landscapes, position-dependent diffusion coefficients, and ultimately the mean first passage time over the step-edges. We find two completely different step-edge crossing mechanisms, the occurrence and rates of which simultaneously depend on both electrostatic and thermal molecule-surface coupling. In weakly coupled systems, the molecule crosses the step relatively quickly (in nanoseconds) by log-roll mechanisms while for strongly coupled systems, it crosses relatively slowly (in microseconds) in a strictly perpendicular fashion. In the latter process, "internal friction" from intramolecular bending and torsional degrees of freedom contribute a significant corrugation to the overall crossing barrier. Furthermore, we show that crossing pathways can also change qualitatively with step-edge height. The great complexity in hetero-barrier crossing of COMs (in contrast to simple atoms) revealed in this study has implications on the interpretation and possible control of nucleation and growth mechanisms at surface defects in hybrid systems.

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Thermally‐activated post‐growth dewetting of fullerene C₆₀ on mica

Cited by 8 publications

References 35 publications

Thin Film Growth of Phase-Separating Phthalocyanine-Fullerene Blends: A Combined Experimental and Computational Study

Thin Film Growth of Phase-Separating Phthalocyanine-Fullerene Blends: A Combined Experimental and Computational Study

Polymorphism and structure formation in copper phthalocyanine thin films

Characterization of step-edge barrier crossing of para-sexiphenyl on the ZnO (101̄0) surface

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Thermally‐activated post‐growth dewetting of fullerene C60 on mica

Cited by 8 publications

References 35 publications

Thin Film Growth of Phase-Separating Phthalocyanine-Fullerene Blends: A Combined Experimental and Computational Study

Thin Film Growth of Phase-Separating Phthalocyanine-Fullerene Blends: A Combined Experimental and Computational Study

Polymorphism and structure formation in copper phthalocyanine thin films

Characterization of step-edge barrier crossing of para-sexiphenyl on the ZnO (101̄0) surface

Contact Info

Product

Resources

About

Thermally‐activated post‐growth dewetting of fullerene C₆₀ on mica