Dokument

Summary:
This thesis deals with the study of the morphology, arrangement and orientation of organic semiconductor films by (scanning) transmission electron microscopy ((S)TEM) techniques. The organic semiconductor perfluoropentacene (PFP) as well as the organic heterostructures of pentacene (PEN) and PFP have been investigated. PFP has been grown on graphene substrate, while the organic mixtures formed by PEN and PFP have been deposited with different mixing ratios on two different substrates, i.e. SiO2 and KCl. PFP deposited on graphene exhibits an epitaxial growth in island shapes where the molecules lie flat and parallel to the substrate adopting the so called ‘π-stacked polymorph’. Within this work, the lateral alignment of the PFP molecules with respect to the graphene substrate has been determined. It was found that the long molecular axis of PFP is aligned along the zig-zag direction of the graphene. However, this alignment is not exactly parallel, but exhibits a small offset. Furthermore, the morphology of the PFP islands has been investigated. A characteristic angle around 68° was found between confining edges of PFP islands. The combination of TEM micrographs and electron diffraction patterns has enabled the determination of the planes that run parallel to the confining edges of the islands ‘as seen’ by the electron beam in the two-dimensional projection. From that the possible side facets associated with each confining edge have been suggested. Finally, electron tomography experiments were used to gain insight into the shape of the PFP islands, allowing the 3D reconstruction of them. PEN:PFP blends have been prepared with mixing ratios of [2:1], [1:1] and [1:2] on an inert substrate such as SiO2. Although different phases and morphologies have been observed for each mixture, a mixed phase made out of PEN and PFP which exhibits similar lattice parameters in all cases has been found independently of the mixing ratio. The monocrystalline SAED pattern of the mixed phase has been shown for the first time on this substrate. The diffraction pattern is rather similar to the one of the pure PEN in �0 0 1� direction, suggesting that the crystal structure of the mixed phase is similar to the one of pure PEN. For non-equimolecular blends, the respective pure phase in excess is present apart from the mixed phase. A different morphology was observed for the different PEN:PFP mixing ratios. The equimolecular mixture of PEN and PFP exhibits fiber-like structures consisting of the mixed phase. For the mixture with PFP in excess, some fibers are formed on a background layer. The PFP is contained in the fibers, while the background layer is made out of the mixed phase. For the mixture with PEN in excess, a grainy structure (grain size of 10 nm-60 nm) with contributions of pure PEN and of the mixed phase is detected. PEN:PFP blends with mixing ratios of [2:1] and [1:2] grown on KCl substrates have been investigated too. The mixed phase formed by PEN and PFP is also present and both blends reveal a quite different morphology. The composition, orientation and crystalline details of each phase have been inspected. In the blend with PEN in excess, the mixed phase together with the pure PEN phase are found in a uniform layer formed with domains that are rotated in-plane by 90° towards each other. In contrast, the blend with excess of PFP presents two different arrangements. The majority of the sample exhibits some spicular fibers made out of PFP on a background layer composed by the mixed phase. The other arrangement present to a lesser extent consists of a film of pure PFP lying in direct contact with the KCl substrate. The importance of PFP grown on graphene lies in the relevance of the graphene substrate together with the π-stacked arrangement exhibited by PFP on this substrate. This motif enhances charge carrier mobility along the stacking direction. The knowledge of the relative alignment as well as the faceting are a key information since the physical properties depend on these parameters. Furthermore, considering the role of the organic heterostructures in the development of organic electronic devices, a detailed understanding of the basic arrangement of the organic molecules in the organic blend is a requirement for the development of new organic devices.

Bibliographie / References

1. R. Brydson, Aberration-Corrected Analytical Transmission Electron Microscopy, 1st ed., John Wiley & Sons, Ltd, 2011. doi:10.1002/9781119978848.
2. H. Usta, A. Facchetti, Polymeric and Small-Molecule Semiconductors for Organic Field-Effect Transistors, in: Large Area Flex. Electron., Wiley-VCH Verlag GmbH & Co. KGaA, 2015: pp. 1-100. doi:10.1002/9783527679973.ch1.
3. G. Horowitz, Organic Semiconductors for new electronic devices, Adv. Mater. 2 (1990) 287-292. doi:10.1002/adma.19900020604.
4. Batlogg, C. Kloc, A polymorph lost and found: The high-temperature crystal structure of pentacene, Adv. Mater. 19 (2007) 2079-2082. doi:10.1002/adma.200602072.
5. G. Dennler, M.C. Scharber, C.J. Brabec, Polymer-Fullerene Bulk-Heterojunction Solar Cells, Adv. Mater. 21 (2009) 1323-1338. doi:10.1002/adma.200801283.
6. [186] X. Wan, G. Long, L. Huang, Y. Chen, Graphene - A Promising Material for Organic Photovoltaic Cells, Adv. Mater. 23 (2011) 5342-5358. doi:10.1002/adma.201102735.
7. [168] P. Ercius, O. Alaidi, M.J. Rames, G. Ren, Electron Tomography: Electron Tomography: A Three-Dimensional Analytic Tool for Hard and Soft Materials Research, Adv. Mater. 27 (2015) 5637. doi:10.1002/adma.201570253.
8. [117] J.E. Anthony, The larger acenes: Versatile organic semiconductors, Angew. Chemie-International Ed. 47 (2008) 452-483. doi:10.1002/anie.200604045.
9. S.A. Maier, Plasmonics: Fundamentals and Applications, 1st ed., Springer US, 2007. doi:10.1007/0-387-37825-1.
10. D.B. Williams, C.B. Carter, Transmission Electron Microscopy. A Textbook for Materials Science, 2nd ed., Springer US, 2009. doi:10.1007/978-0-387-76501-3.
11. W. Kowalsky, E. Becker, T. Benstem, H.-H. Johannes, D. Metzdorf, H. Neuner, J. Schöbel, Organic semiconductors: fundamentals and applications BT - Advances in Solid State Physics 40, in: B. Kramer (Ed.), Springer Berlin Heidelberg, Berlin, Heidelberg, 2000: pp. 795-808. doi:10.1007/BFb0108396.
12. A.H. Andersen, A.C. Kak, Simultaneous Algebraic Reconstruction Technique (SART): A superior implementation of the ART algorithm, Ultrason. Imaging. 6 (1984) 81-94. doi:10.1016/0161-7346(84)90008-7.
13. [112] P.A. Stadelmann, EMS - A Software package for electron-diffraction analysis and HREM image simulation in materials science, Ultramicroscopy. 21 (1987) 131- 145. doi:10.1016/0304-3991(87)90080-5.
14. [157] P. Hartel, H. Rose, C. Dinges, Conditions and reasons for incoherent imaging in STEM, Ultramicroscopy. 63 (1996) 93-114. doi:10.1016/0304-3991(96)00020-4.
15. [172] P. Gilbert, Iterative methods for the three-dimensional reconstruction of an object from projections., J. Theor. Biol. 36 (1972) 105-117. doi:10.1016/j.jsb.2005.10.005.
16. H.B. Wang, J. Wang, H.C. Huang, X.J. Yan, D.H. Yan, Organic heterojunction with reverse rectifying characteristics and its application in field-effect transistors, Org. Electron. 7 (2006) 369-374. doi:10.1016/j.orgel.2006.04.004.
17. [209] S. Pratontep, M. Brinkmann, F. Nuesch, L. Zuppiroli, Nucleation and growth of ultrathin pentacene films on silicon dioxide: effect of deposition rate and substrate temperature, Synth. Met. 146 (2004) 387-391. doi:10.1016/j.synthmet.2004.08.017.
18. A. Pron, P. Rannou, Processible conjugated polymers: from organic semiconductors to organic metals and superconductors, Prog. Polym. Sci. 27 (2002) 135-190. doi:10.1016/S0079-6700(01)00043-0.
19. C.C. Mattheus, A.B. Dros, J. Baas, G.T. Oostergetel, A. Meetsma, J.L. de Boer, T.T.M. Palstra, Identification of polymorphs of pentacene, Synth. Met. 138 (2003) 475-481. doi:10.1016/s0379-6779(02)00467-8.
20. [110] I.P.M. Bouchoms, W.A. Schoonveld, J. Vrijmoeth, T.M. Klapwijk, Morphology identification of the thin film phases of vacuum evaporated pentacene on SIO2 substrates, Synth. Met. 104 (1999) 175-178. doi:10.1016/s0379-6779(99)00050-8.
21. H.-K. Seo, M.-H. Park, Y.-H. Kim, S.-J. Kwon, S.-H. Jeong, T.-W. Lee, Laminated Graphene Films for Flexible Transparent Thin Film Encapsulation, ACS Appl. Mater. Interfaces. 8 (2016) 14725-14731. doi:10.1021/acsami.6b01639.
22. B. Haas, K.I. Gries, T. Breuer, I. Häusler, G. Witte, K. Volz, Microstructural Characterization of Organic Heterostructures by (Transmission) Electron Microscopy, Cryst. Growth Des. 14 (2014) 3010-3014. doi:10.1021/cg5002896.
23. [107] S. Schiefer, M. Huth, A. Dobrinevski, B. Nickel, Determination of the crystal structure of substrate-induced pentacene polymorphs in fiber structured thin films, J. Am. Chem. Soc. 129 (2007) 10316-10317. doi:10.1021/ja0730516.
24. [133] I. Salzmann, S. Duhm, G. Heimel, M. Oehzelt, R. Kniprath, R.L. Johnson, J.P. Rabe, N. Koch, Tuning the ionization energy of organic semiconductor films: The role of intramolecular polar bonds, J. Am. Chem. Soc. 130 (2008) 12870-12871. doi:10.1021/ja804793a.
25. [210] S.D. Wang, X. Dong, C.S. Lee, S.T. Lee, Molecular orientation and film morphology of pentacene on native silicon oxide surface, J. Phys. Chem. B. 109 (2005) 9892-9896. doi:10.1021/jp046490p.
26. [134] S. Kowarik, K. Broch, A. Hinderhofer, A. Schwartzberg, J.O. Osso, D. Kilcoyne, F. Schreiber, S.R. Leone, Crystal Grain Orientation in Organic Homo- and Heteroepitaxy of Pentacene and Perfluoropentacene Studied with X-ray Spectromicroscopy, J. Phys. Chem. C. 114 (2010) 13061-13067. doi:10.1021/jp103713z.
27. [116] J. Götzen, C.H. Schwalb, C. Schmidt, G. Mette, M. Marks, U. Hoefer, G. Witte, Structural Evolution of Perfluoro-Pentacene Films on Ag(111): Transition from 2D to 3D Growth, Langmuir. 27 (2011) 993-999. doi:10.1021/la1022664.
28. [115] I. Salzmann, S. Duhm, G. Heimel, J.P. Rabe, N. Koch, M. Oehzelt, Y. Sakamoto, T. Suzuki, Structural order in perfluoropentacene thin films and heterostructures with pentacene, Langmuir. 24 (2008) 7294-7298. doi:10.1021/la800606h.
29. [188] X. Wang, L. Zhi, K. Muellen, Transparent, conductive graphene electrodes for dye-sensitized solar cells, Nano Lett. 8 (2008) 323-327. doi:10.1021/nl072838r.
30. [180] J. Wu, M. Agrawal, H.A. Becerril, Z. Bao, Z. Liu, Y. Chen, P. Peumans, Organic Light-Emitting Diodes on Solution-Processed Graphene Transparent Electrodes, ACS Nano. 4 (2010) 43-48. doi:10.1021/nn900728d.
31. [187] L. Gomez De Arco, Y. Zhang, C.W. Schlenker, K. Ryu, M.E. Thompson, C. Zhou, Continuous, highly flexible, and transparent graphene films by chemical vapor deposition for organic photovoltaics, ACS Nano. 4 (2010) 2865-2873. doi:10.1021/nn901587x.
32. [123] P. Peumans, S. Uchida, S.R. Forrest, Efficient bulk heterojunction photovoltaic cells using small-molecular-weight organic thin films, Nature. 425 (2003) 158- 162. doi:10.1038/nature01949.
33. [179] K.P. Loh, Q. Bao, G. Eda, M. Chhowalla, Graphene oxide as a chemically tunable platform for optical applications, Nat Chem. 2 (2010) 1015-1024. doi:10.1038/nchem.907.
34. H. Sirringhaus, Organic semiconductors: An equal-opportunity conductor, Nat Mater. 2 (2003) 641-642. doi:10.1038/nmat988.
35. [184] J.-H. Chen, C. Jang, S. Xiao, M. Ishigami, M.S. Fuhrer, Intrinsic and extrinsic performance limits of graphene devices on SiO2, Nat Nano. 3 (2008) 206-209. doi:10.1038/nnano.2008.58.
36. [185] S. Bae, H. Kim, Y. Lee, X. Xu, J.-S. Park, Y. Zheng, J. Balakrishnan, T. Lei, H. Ri Kim, Y. Il Song, Y.-J. Kim, K.S. Kim, B. Ozyilmaz, J.-H. Ahn, B.H. Hong, S. Iijima, Roll-to-roll production of 30-inch graphene films for transparent electrodes, Nat Nano. 5 (2010) 574-578. doi:10.1038/nnano.2010.132.
37. [132] F. Babudri, G.M. Farinola, F. Naso, R. Ragni, Fluorinated organic materials for electronic and optoelectronic applications: the role of the fluorine atom, Chem. Commun. (2007) 1003-1022. doi:10.1039/b611336b.
38. C. Yan, J.H. Cho, J.-H. Ahn, Graphene-based flexible and stretchable thin film transistors, Nanoscale. 4 (2012) 4870-4882. doi:10.1039/C2NR30994G.
39. [124] [125] [126] [127] [128] [129] [130] [131] [122] S. Jia, H.D. Sun, J.H. Du, Z.K. Zhang, D.D. Zhang, L.P. Ma, J.S. Chen, D.G. Ma, H.M. Cheng, W.C. Ren, Graphene oxide/graphene vertical heterostructure electrodes for highly efficient and flexible organic light emitting diodes, Nanoscale. 8 (2016) 10714-10723. doi:10.1039/c6nr01649a.
40. H. Klauk, M. Halik, U. Zschieschang, G. Schmid, W. Radlik, W. Weber, Highmobility polymer gate dielectric pentacene thin film transistors, J. Appl. Phys. 92 (2002) 5259-5263. doi:10.1063/1.1511826.
41. [118] J. Wang, H.B. Wang, X.J. Yan, H.C. Huang, D.H. Yan, Organic heterojunction and its application for double channel field-effect transistors, Appl. Phys. Lett. 87 (2005) 93507. doi:10.1063/1.2037204.
42. K.M. Lau, J.X. Tang, H.Y. Sun, C.S. Lee, S.T. Lee, D.H. Yan, Interfacial electronic structure of copper phthalocyanine and copper hexadecafluorophthalocyanine studied by photoemission, Appl. Phys. Lett. 88 (2006) 173513. doi:10.1063/1.2198484.
43. [189] J. Wu, H.A. Becerril, Z. Bao, Z. Liu, Y. Chen, P. Peumans, Organic solar cells with solution-processed graphene transparent electrodes, Appl. Phys. Lett. 92 (2008) 263302. doi:10.1063/1.2924771.
44. A. Hinderhofer, C. Frank, T. Hosokai, A. Resta, A. Gerlach, F. Schreiber, Structure and morphology of coevaporated pentacene-perfluoropentacene thin films, J. Chem. Phys. 134 (2011) 104702. doi:10.1063/1.3557476.
45. A. Moser, J. Novak, H.-G. Flesch, T. Djuric, O. Werzer, A. Haase, R. Resel, Temperature stability of the pentacene thin-film phase, Appl. Phys. Lett. 99 (2011) 221911. doi:10.1063/1.3665188.
46. [137] F. Anger, J.O. Ossó, U. Heinemeyer, K. Broch, R. Scholz, A. Gerlach, F. Schreiber, Photoluminescence spectroscopy of pure pentacene, perfluoropentacene, and mixed thin films, J. Chem. Phys. 136 (2012) 54701. doi:10.1063/1.3677839.
47. L. von Helden, T. Breuer, G. Witte, Anisotropic thermal expansion in pentacene and perfluoropentacene: Effects of molecular packing motif and fixation at the interface, Appl. Phys. Lett. 110 (2017) 141904. doi:10.1063/1.4979650.
48. E. Rutherford, LXXIX. The scattering of α and β particles by matter and the structure of the atom, Philos. Mag. 21 (1911) 669-688. doi:10.1080/14786440508637080.
49. L. de Broglie, XXXV. A tentative theory of light quanta, Philos. Mag. Ser. 6. 47 (1924) 446-458. doi:10.1080/14786442408634378.
50. London A Math. Phys. Eng. Sci. 358 (2000) 173-192. doi:10.1098/rsta.2000.0526.
51. [181] A.H. Castro Neto, F. Guinea, N.M.R. Peres, K.S. Novoselov, A.K. Geim, The electronic properties of graphene, Rev. Mod. Phys. 81 (2009) 109-162. doi:10.1103/RevModPhys.81.109.
52. R.B. Campbell, J.M. Robertson, J. Trotter, The crystal structure of hexacene, and a revision of the crystallographic data for tetracene and pentacene, Acta Crystallogr. 15 (1962) 289-290. doi:10.1107/S0365110X62000699.
53. [192] S. Park, S.H. Shin, M.N. Yogeesh, A.L. Lee, S. Rahimi, D. Akinwande, Extremely High-Frequency Flexible Graphene Thin-Film Transistors, IEEE Electron Device Lett. 37 (2016) 512-515. doi:10.1109/LED.2016.2535484.
54. [182] Y.-M. Lin, C. Dimitrakopoulos, K.A. Jenkins, D.B. Farmer, H.-Y. Chiu, A. Grill, P. Avouris, 100-GHz Transistors from Wafer-Scale Epitaxial Graphene, Science. 327 (2010) 662. doi:10.1126/science.1184289.
55. G. Henderson, D. Neuville, R. Downs, Spectroscopic Methods in Mineralogy and Material Sciences, Mineralogical Society of America, 2014. doi:10.2138/am2014-655.
56. N.M. Asl, A. Sadremomtaz, Analytical image reconstruction methods in emission tomography, J. Biomed. Sci. Eng. 6 (2013) 27659. doi:10.4236/jbise.2013.61013.
57. The 14 Bravais lattices, (2017). http://img.tfd.com/mgh/cep/The-14-Bravaislattices-derived-by-centering-of-the-seven-crystal.jpg (accessed May 23, 2017).
58. H. Rose, W. Wan, Aberration Correction in Electron Microscopy, Proc. 2005 Part.
59. T. Siegrist, C. Kloc, J.H. Schön, B. Batlogg, R.C. Haddon, S. Berg, G.A. Thomas, Enhanced physical properties in a pentacene polymorph, Angew. ChemieInternational Ed. 40 (2001) 1732-1736. doi:10.1002/1521-3773(20010504)40:9<1732::aidanie17320>3.0.co;2-7.
60. N. Zhou, A. Facchetti, Charge Transport and Recombination in Organic Solar Cells (OSCs), in: H. Huang, J. Huang (Eds.), Org. Hybrid Sol. Cells, Springer International Publishing, Cham, 2014: pp. 19-52. doi:10.1007/978-3-319-10855- 1_2.
61. Tokito, Perfluoropentacene: High-performance p-n junctions and complementary circuits with pentacene, J. Am. Chem. Soc. 126 (2004) 8138-8140.
62. K. Broch, C. Bürker, J. Dieterle, S. Krause, A. Gerlach, F. Schreiber, Impact of molecular tilt angle on the absorption spectra of pentacene: perfluoropentacene blends, Phys. Status Solidi-Rapid Res. Lett. 7 (2013) 1084-1088.
63. E.A. Silinsh, V. Capek, Organic Molecular Crystals: Interaction, Localization and Transport Phenomena, American Chemical Society, New York, 1994.
64. O.D. Jurchescu, M. Popinciuc, B.J. van Wees, T.T.M. Palstra, Interfacecontrolled, high-mobility organic transistors, Adv. Mater. 19 (2007) 688-692.
65. Schreiber, Optical evidence for intermolecular coupling in mixed films of pentacene and perfluoropentacene, Phys. Rev. B. 83 (2011) 245307.
66. Y. Inoue, Y. Sakamoto, T. Suzuki, M. Kobayashi, Y. Gao, S. Tokito, Organic thinfilm transistors with high electron mobility based on perfluoropentacene, Japanese J. Appl. Phys. Part 1-Regular Pap. Br. Commun. Rev. Pap. 44 (2005) 3663-3668.
67. C.C. Mattheus, A.B. Dros, J. Baas, A. Meetsma, J.L. de Boer, T.T.M. Palstra, Polymorphism in pentacene, Acta Crystallogr. Sect. C. 57 (2001) 939-941.
68. A. Girlando, M. Masino, A. Brillante, T. Toccoli, S. Iannotta, Raman Identification of Polymorphs in Pentacene Films, Crystals. 6 (2016).
69. A. Ott, Structural characterization of antimonide-based metamorphic buffer layers on (001) silicon substrate, PhD Thesis, Philipps-Universität Marburg, 2016.
70. L.F. Drummy, D.C. Martin, Thickness-Driven Orthorhombic to Triclinic Phase Transformation in Pentacene Thin Films, Adv. Mater. 17 (2005) 903-907.
71. L. Reimer, Transmission Electron Microscopy. Physics of Image Formation and Microanalysis, 4th ed., Springer Berlin Heidelberg, 1997. doi:10.1007/978-3-662- 14824-2.
72. V. Gohri, S. Hofmann, S. Reineke, T. Rosenow, M. Thomschke, M. Levichkova, B. Lussem, K. Leo, White top-emitting organic light-emitting diodes employing a heterostructure of down-conversion layers, Org. Electron. 12 (2011) 2126-2130.
73. T. Walther, Y. Qiu, A.G. Cullis, Measuring the contrast in annular dark field STEM images as a function of camera length, J. Phys. Conf. Ser. 241 (2010) 12068. http://stacks.iop.org/1742-6596/241/i=1/a=012068.
74. F. Krumeich, Properties of Electrons, their Interactions with Matter and Applications in Electron Microscopy, (2014). http://www.microscopy.ethz.ch/downloads/Interactions.pdf.
75. https://www.iapp.de/orgworld.de/?Basics:What_are_organic_semiconductors (accessed February 2, 2017).

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