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both(Degrees and distances) are used in research reported in the literature (see [ 16 , 17 , 18 ]). Pentacene is one of the most popular hydrocarbon semiconductors in chemistry [ 19 ]. The name pentacene is a combination of two words: penta, meaning five, and acene, which refers to polycyclic aromatic hydrocarbons with fused benzene rings. The importance of pentacene has dramatically increased in recent years due to its key roles in electronic devices and organic solar cells. As the price of energy rises day by day, researchers continue to look for cheaper sources

”, Adv. Mater., Vol. 15(1), (2003), pp. 33–38. http://dx.doi.org/10.1002/adma.200390003 [6] M. Pope and C.E. Swenberg: Electronic Process in Organic Crystals and Polymers, Oxford University Press, New York, 1999. [7] G. Horowitz, D. Fichou, A. Yassar et al.: “Molecular order in organic-based field-effect transistors”, Synth. Met., Vol. 81(2–3), (1992), pp. 163–171. [8] O. Jurchescu, J. Baas and T. Palstra: “Effect of impurities on the mobility of single crystal pentacene” Appl. Phys. Lett., Vol. 84(16), (2004), pp. 3061–3063. http://dx.doi.org/10.1063/1.1704874 [9] J

Abstract

To improve Organic Thin Film Transistor (OTFT) properties we study OTFT semiconductor/dielectric interfacial properties via examination of the gate dielectric using thin Parylene C layer. Structural and morphology properties of pentacene layers deposited on parylene layer and SiO2/Si substrate structure were compared. The surface morphology was investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM topography of pentacene layer in non-contact mode confirmed the preferable pentacene grain formation on parylene surface in dependence on layer thickness. The distribution of chemical species on the surfaces and composition depth profiles were measured by secondary ion mass spectroscopy (SIMS) and surface imaging. The depth profiles of the analyzed structures show a homogenous pentacene layer, characterized with C or C2 ions. Relatively sharp interface between pentacene and parylene layers was estimated by characteristic increased intensity of CCl ions peak. For revealing the pentacene phases in the structures the Micro-Raman spectroscopy was utilized. Conformal coatings of parylene and pentacene layers without pinholes resulted from the deposition process as was confirmed by SIMS surface imaging. For the pentacene layers thicker than 20 nm, both thin and bulk pentacene phases were detected by Micro-Raman spectroscopy, while for the pentacene layer thickness of 5 and 10 nm the preferable thin phase was detected. The complete characterisation of pentacene layers deposited on SiO2 and parylene surface revealed that the formation of large grains suggests 3D pentacene growth at parylene layer with small voids between grains and more than one monolayer step growth. The results will be utilized for optimization of the deposition process.

-Channel Organic Thin Film Transistors”, J. Am. Chem. Soc., Vol. 120(1), (1998), pp. 207–208. http://dx.doi.org/10.1021/ja9727629 [7] M. Vujicic, I.B. Bozovic and F. Herbut: “Construction of symmetry groups of polymer molecules”, J. Phys. A-Math. Gen., Vol. 10, (1977), pp. 1271–1279. http://dx.doi.org/10.1088/0305-4470/10/8/005 [8] L. Michel: “Symmetry defects and broken symmetry. Configurations Hidden Symmetry”, Rev. Mod. Phys., Vol. 52, (1980), pp. 617–651. http://dx.doi.org/10.1103/RevModPhys.52.617 [9] C.C. Matthews: Polymorphism and electronic properties of pentacene

Abstract

Organic films fabrication offers the possibility of producing electronic devices of low weight, mechanical flexibility and low cost. One suitable material for organic film fabrigation which is the subject of the great interest is pentacene, because it is characterized by the large carrier mobility (∼1 cm2/Vs).

In this work, the growth of pentacene layers using pulse laser deposition (PLD) on different substrates (glass/ITO, Si) is described and various processing parameters are investigated. Two pulsed YAG:Nd3+ laser wavelengths were used for the ablation of the PLD target: the first harmonic at 1064 nm aGn:dNdth3+e second at 532 nm. The structure of the layers formed was examined using SEM and RHEED methods. The results were compared with results of optical spectroscopy studies. It will be shown that layers deposed using second harmonics have a higher quality than those for first harmonic. The other PLD parametersalso have a strong influence on the structure quality of layers.

conductive thin films of pentacene”, J. Appl. Phys., Vol. 72, (1992), pp. 5220–5225. http://dx.doi.org/10.1063/1.352004 [7] Y. Matsuo, A. Sasaki, Y. Yoshida and S. Ikehata: “New state structure of iodine doped pentacene film”, Material Science and Engineering, Vol. B60, (1990), pp. 133–136. [8] Y. Matsuo, A. Sasaki, Y. Yoshida and S. Ikehata: “New stage structure of iodine doped pentacene film (II)”, Mol. Cryst. Liq. Cryst., Vol. 340, (2000), pp. 223–228. [9] Y. Matsuo, T. Ijichi, J. Hatori and S. Ikehata: “Fabrication and electrical properties of field effect transistor

Introduction We disclose here the synthesis of a series of novel N,N′-dihydroazatetracenes, -pentacenes and -heptacenes and the attempt to oxidize them into azaacenes. We observe significant structure dependent differences in stability of the targets. N-Heteroacenes have received increasing attention in the last few years [1]. Compounds of this type have been the subject of research for more than a century, and were first independently synthesized by Fischer and by Hinsberg at the end of the 19 th and the beginning of the 20 th centuries [2]. Hinsberg noted

Abstract

Charge-carrier transport in the channel of bottom gate, top contact organic field effect transistors with anisotropic layers of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pentacene) obtained by zone casting was investigated using scanning Kelvin probe microscopy combined with atomic force microscopy. The TIPS-Pentacene continuous layers consisted of thin crystals unidirectionally oriented in the channel. Devices with perpendicular and parallel charge flow in the transistor channel were prepared. It was found that irregularities in the surface morphology at the semiconductor layer in the transistor channel are correlated with the local potential profile, and that the channel resistance strongly depends on the orientation of the TIPS-Pentacene crystals.

and spectroscopic properties of new soluble disubstituted acenes (anthracene, tetracene, pentacene) are reported. It is shown that the 2,3-alkoxy derivatives gel a large variety of organic solvents, a process that is related to the linear shape of the mole- cule. The gelation involves the formation of nanofibers through noncovalent interactions (van der Waals, π−π stacking), weaving a 3D supramolecular network or a deposit made of iso- lated fibers on surfaces (mica or graphite). Transport of photons through this type of nano- structure has been evidenced by the

linear con- densed aromatic gelators are reported. The gels formed by 2,3-alkoxy derivatives are consti- tuted of nanofibers weaving a 3-dimensional supramolecular network and imprisoning the solvent. These nanofibers are efficient light-harvesting systems in which complete energy transfer toward a fluorescent acceptor can be achieved at doping levels below 1 mol % of ac- ceptor. Keywords: organogelators; energy transfer; fluorescence; tetracene; pentacene. INTRODUCTION The development of nanostructures with designed optical properties represents a major interest for