Pentacene organic thin-film transistors for circuit and display applications

Klauk, Hagen; Gundlach, David J.; Nichols, J. A.; Jackson, Thomas N.

doi:10.1109/16.766895

Cited by 271 publications

(131 citation statements)

References 16 publications

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“…[16][17][18][19][20] For the structural properties of this particular interface, we will show that pentacene forms ordered domains when deposited at elevated temperatures on polycrystalline Co films, with an almost perpendicular orientation of the molecules to the substrate. Because of the large ordered areas formed on the polycrystalline substrate, one would not expect a very strong interaction to take place.…”

Section: Introductionmentioning

confidence: 99%

Morphology and electronic properties of the pentacene on cobalt interface

Tiba

Jonge

Koopmans

et al. 2006

Journal of Applied Physics

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In this paper, we report the structural and electronic properties of pentacene thin films grown on a polycrystalline Co film using atomic force microscopy and ultraviolet photoemission spectroscopy ͑UPS͒, respectively. Investigation of this type of interface is of importance for the engineering of hybrid organometallic spintronic devices for which the use of spin polarized electrodes is a prerequisite. Uniform single crystalline areas of pentacene as large as several micrometers, with molecules arranging almost perpendicular to the substrate, were obtained. For the electronic properties at this interface, we have found an energy barrier for the hole injection of about 1 eV, in spite of the fact that the ionization potential of pentacene reported previously equals the work function of Co. A shift of the vacuum level of the same magnitude has also been observed. A comparison of the UPS spectra of the pentacene films with the gas phase spectrum directly indicates that hybridization effects are present at this interface. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2363707͔ INTRODUCTIONMolecular organic semiconductors have become a very active area of research during the past decade. The structural flexibility due to weak intermolecular bonds and the endless possibilities for chemical synthesis of new molecules give molecular systems a unique advantage over inorganic semiconductors for relatively simple fabrication of ͑opto-͒ electronic devices such as light emitting diodes for flexible or even transparent displays, transistors, solar cells, sensors, and solid state lasers. Applications into electronic devices in which the spin degree of freedom of the electron is exploited ͑spintronics͒ have recently started to be considered, motivated by the notion that organic semiconductors are materials with large spin relaxation times. [1][2][3][4][5] Spin valves with a significant magnetoresistance have been produced with Alq 3 thin films sandwiched between two ferromagnetic electrodes. 4,5 In response to the technological success of the organic semiconductors, fundamental research, with the goal of understanding the surface and interface properties of these systems, has followed. Such studies have proven to be valuable for device engineering, as well as from the fundamental viewpoint, electronic properties of interfaces between organic semiconductors and metals being still puzzling for scientists. While the electronic and structural properties of large organic molecules on noble metals and semiconducting or semimetallic substrates have been extensively studied, only a limited number of studies on more reactive substrates, such as the ferromagnetic transition metals, have been reported. 6 Such investigations are of crucial relevance to understand and control efficient spin injection from ferromagnetic electrodes into organic thin films.In the ferromagnetic transition metals, both the magnetic behavior and the reactivity originate from the high density of the d states near the Fermi level. For the structural propertie...

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Section: Introductionmentioning

confidence: 99%

Morphology and electronic properties of the pentacene on cobalt interface

Tiba

Jonge

Koopmans

et al. 2006

Journal of Applied Physics

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“…Oligoacenes are flexible, cheap, and exhibit relatively high charge carrier mobilities, 1 allowing for novel applications in electronic devices. [2][3][4] Despite this interest, the nature of charge transport in the materials has remained the subject of intense debate.Crystalline organic semiconductors exhibit charge mobilities that decrease with temperature. [5][6][7][8][9] In analogy to inorganic semiconductors, this has been interpreted as an indication of delocalized charge carriers and a "bandlike" transport mechanism.…”

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confidence: 99%

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On the mechanism of charge transport in pentacene

Laarhoven

Flipse

Koeberg³

et al. 2008

The Journal of Chemical Physics

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Terahertz transient conductivity measurements are performed on pentacene single crystals, which directly demonstrate a strong coupling of charge carriers to low frequency molecular motions with energies centered around 1.1 THz. We present evidence that the strong coupling to low frequency motions is the factor limiting the conductivity in these organic semiconductors. Our observations explain the apparent paradox of the "bandlike" temperature dependence of the conductivity beyond the validity limit of the band model. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2955462͔Recent years have seen much interest in the conductivity of pentacene and other molecular semiconductors of the oligoacene family, fueled by the unique properties of these materials. Oligoacenes are flexible, cheap, and exhibit relatively high charge carrier mobilities, 1 allowing for novel applications in electronic devices. [2][3][4] Despite this interest, the nature of charge transport in the materials has remained the subject of intense debate.Crystalline organic semiconductors exhibit charge mobilities that decrease with temperature. [5][6][7][8][9] In analogy to inorganic semiconductors, this has been interpreted as an indication of delocalized charge carriers and a "bandlike" transport mechanism. 10-13 Theoretical models based on polaronic band conduction 14 indeed provide a good qualitative description of the bandlike mobility of charge carriers in pentacene, but the factors determining the absolute charge mobility remain unknown. For instance, an analysis of the high temperature mobility has indicated that the mean free path of charge carriers is of the same magnitude as the intermolecular distance. 15 It is not clear as to why the signature of delocalized bandlike transport persists at these temperatures, where the mean free path is smaller than the intermolecular distances. Because of the "softness" of these van der Waals bonded organic crystals, it is possible that the coupling of the carriers with the intermolecular vibrations could play a key role in the description of the charge carrier dynamics. Troisi and Orlandi 16 have recently formulated a model ͑TO model͒ that states that the charge mobility in oligoacenes is limited by large fluctuations of the electronic coupling between adjacent organic molecules due to thermal molecular motions, in particular, the low energetic phonon modes with energies around 1 THz. 17 This model correctly describes the bandlike temperature dependence of the mobility, including its absolute value, outside the validity of delocalized transport models. 16 Direct experimental evidence for the various proposed models has been lacking. In particular, experimental insights into the role of intermolecular low frequency vibrational modes in determining the charge transport mechanism have been missing to date.Terahertz spectroscopy 18 provides the opportunity of studying the response of charge carriers in the frequency range of these modes, and has proven useful for investigating photocarrier dynamics in...

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“…The first OFET-devices were developed using silicon dioxide, a standard dielectric material in MOSFET technology. The growth process of SiO2 can be well-controlled, providing a low defect density and a smooth surface to produce well-oriented organic semiconducting films [44][45][46]. Besides the high electrical stability, thermally grown SiO2 on a heavily doped Si wafer acts as template to evaluate new synthesized organic semiconducting materials.…”

Section: Organic Based Tftmentioning

confidence: 99%

Flexible Electronics: Integration Processes for Organic and Inorganic Semiconductor-Based Thin-Film Transistors

2015

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Flexible and transparent electronics have been studied intensively during the last few decades. The technique establishes the possibility of fabricating innovative products, from flexible displays to radio-frequency identification tags. Typically, large-area polymeric substrates such as polypropylene (PP) or polyethylene terephthalate (PET) are used, which produces new requirements for the integration processes. A key element for flexible and transparent electronics is the thin-film transistor (TFT), as it is responsible for the driving current in memory cells, digital circuits or organic light-emitting devices (OLEDs). In this paper, we discuss some fundamental concepts of TFT technology. Additionally, we present a comparison between the use of the semiconducting organic small-molecule pentacene and inorganic nanoparticle semiconductors in order to integrate TFTs suitable for flexible electronics. Moreover, a technique for integration with a submicron resolution suitable for glass and foil substrates is presented.

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Pentacene organic thin-film transistors for circuit and display applications

Cited by 271 publications

References 16 publications

Morphology and electronic properties of the pentacene on cobalt interface

Morphology and electronic properties of the pentacene on cobalt interface

On the mechanism of charge transport in pentacene

Flexible Electronics: Integration Processes for Organic and Inorganic Semiconductor-Based Thin-Film Transistors

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