The Effect of the Ambient Oxygen on the Electrical Properties of an Evaporated Film of Pentacene

Kuroda, Haruo; Flood, E. A.

doi:10.1139/v61-267

Cited by 14 publications

(5 citation statements)

References 7 publications

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“…The increased conductivity is ascribed to an increased charge carrier density caused by doping. [43,44,45] There seems to be no evidence that doping leads to an increased effective mobility in pentacene. Recent measurements on rubrene single crystals also show doping not to increase the fieldeffect mobility.…”

Section: Influence Of Oxygen and Nitrogenmentioning

confidence: 99%

“…Doping is observed when pentacene thin films are exposed to relatively high partial pressures (0.01 atm-1 atm) of oxygen or nitrogen in the presence of light. [42,43,45] The doping effect by oxygen is reported to be negligible in the absence of light. [42,43] Ultraviolet photoelectron spectroscopy (UPS) before and after exposure to 5×10 −6 mbar oxygen could not detect a lasting effect on the position of the energy levels.…”

Section: Influence Of Oxygen and Nitrogenmentioning

confidence: 99%

“…[42,43,45] The doping effect by oxygen is reported to be negligible in the absence of light. [42,43] Ultraviolet photoelectron spectroscopy (UPS) before and after exposure to 5×10 −6 mbar oxygen could not detect a lasting effect on the position of the energy levels. [47] According to Ref.…”

Section: Influence Of Oxygen and Nitrogenmentioning

confidence: 99%

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Defect healing at room temperature in pentacene thin films and improved transistor performance

et al. 2007

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We report on a healing of defects at room temperature in the organic semiconductor pentacene. This peculiar effect is a direct consequence of the weak intermolecular interaction which is characteristic of organic semiconductors. Pentacene thin-film transistors were fabricated and characterized by in situ gated four-terminal measurements. Under high vacuum conditions (base pressure of order 10 −8 mbar), the device performance is found to improve with time. The effective field-effect mobility increases by as much as a factor of two and mobilities up to 0.45 cm 2 /Vs were achieved. In addition, the contact resistance decreases by more than an order of magnitude and there is a significant reduction in current hysteresis. Oxygen/nitrogen exposure and annealing experiments show the improvement of the electronic parameters to be driven by a thermally promoted process and not by chemical doping. In order to extract the spectral density of trap states from the transistor characteristics, we have implemented a powerful scheme which allows for a calculation of the trap densities with high accuracy in a straightforward fashion. We show the performance improvement to be due to a reduction in the density of shallow traps ≤ 0.15 eV from the valence band edge, while the energetically deeper traps are essentially unaffected. This work contributes to an understanding of the shallow traps in organic semiconductors and identifies structural point defects within the grains of the polycrystalline thin films as a major cause.

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Section: Influence Of Oxygen and Nitrogenmentioning

confidence: 99%

Section: Influence Of Oxygen and Nitrogenmentioning

confidence: 99%

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Defect healing at room temperature in pentacene thin films and improved transistor performance

et al. 2007

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“…It is widely believed that such p-type OSCs are unintentionally doped by oxygen from air. [1][2][3] The properties of organic electronic devices such as sensors, transistors, and light-emitting diodes are affected by oxygen gas. [4][5][6] In an oxygen doping process, an electron is transferred to an oxygen molecule, and a molecular cation and an oxygen anion are formed.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced Doping of Organic Field Effect Transistors Studied by Displacement Current Measurement and Infrared Absorption Spectroscopy in Multiple Internal Reflection Geometry

Ogawa

Naijo

Kimura

et al. 2006

jjap

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PACS. 62.20 -Mechanical properties of solids (related to microscopic structure). PACS. 62.65 -Acoustic properties of solids. PACS. 61.40 -Amorphous and polymeric materials.Abstract. -In icosahedral quasi-crystals the second-order elastic constant tensor is known theoretically and experimentally to be isotropic; however, elastic isotropy does not hold if higher-order elasticity tensors are considered. In particular the stress dependence of sound velocities which involves at least a sixth-rank tensor is expected to be anisotropic in quasi-crystals. In this paper, the pressure dependence of sound velocities is calculated for both longitudinal and shear ultrasonic waves propagating in an icosahedral structure and the fist measurements of sound velocities in a quasi-crystal under pressure are reported; the longitudinal and shear waves velocities are also measured from 4 to 300 K. The temperature dependence of sound velocities c o n f i i s the elastic isotropy, while the pressure dependence exibits an unusual behaviour.

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“…It is well known that pentacene is easily oxidized in solution, 9) whereas it is quite stable in the crystalline state. 10) This result suggests that pentacene molecules may not be oxidized in a low pressure O 2 ambient even when they are heated. More interestingly, note that the mobility of the TFTs prepared in H 2 was significantly improved.…”

mentioning

confidence: 99%

Grain Size Increase and Field-Effect Mobility Enhancement of Pentacene Thin Films Prepared in a Low-Pressure H₂Ambient

Yokoyama¹,

Park²,

Nagashio³

et al. 2008

Appl. Phys. Express

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Pentacene films were grown by thermal evaporation in different gas atmospheres at a relatively low vacuum of about 3 Pa, and the effects of the gas ambient on the performance of thin film transistors (TFTs) were investigated. The TFT mobility of film deposited in H2 was twice the typical value of 0.3 cm2/(V·s) for film deposited in vacuum, while the mobility values of films deposited in N2 and O2 were almost the same as that of vacuum-deposited film. No significant changes in on/off ratio, threshold voltage, or hysteresis behavior were observed in pentacene TFTs prepared by evaporation in gas ambient. The improved mobility of pentacene film prepared in H2 can be explained by an increase in grain size of the first layer on the SiO2/Si substrate.

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The Effect of the Ambient Oxygen on the Electrical Properties of an Evaporated Film of Pentacene

Cited by 14 publications

References 7 publications

Defect healing at room temperature in pentacene thin films and improved transistor performance

Defect healing at room temperature in pentacene thin films and improved transistor performance

Photoinduced Doping of Organic Field Effect Transistors Studied by Displacement Current Measurement and Infrared Absorption Spectroscopy in Multiple Internal Reflection Geometry

Grain Size Increase and Field-Effect Mobility Enhancement of Pentacene Thin Films Prepared in a Low-Pressure H₂Ambient

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The Effect of the Ambient Oxygen on the Electrical Properties of an Evaporated Film of Pentacene

Cited by 14 publications

References 7 publications

Defect healing at room temperature in pentacene thin films and improved transistor performance

Defect healing at room temperature in pentacene thin films and improved transistor performance

Photoinduced Doping of Organic Field Effect Transistors Studied by Displacement Current Measurement and Infrared Absorption Spectroscopy in Multiple Internal Reflection Geometry

Grain Size Increase and Field-Effect Mobility Enhancement of Pentacene Thin Films Prepared in a Low-Pressure H2Ambient

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Grain Size Increase and Field-Effect Mobility Enhancement of Pentacene Thin Films Prepared in a Low-Pressure H₂Ambient