Physical vapor growth of organic semiconductors

Laudise, R.A.; Kloc, Ch.; Simpkins, P. G.; Siegrist, T.

doi:10.1016/s0022-0248(98)00034-7

Cited by 628 publications

(513 citation statements)

References 11 publications

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“…Single crystals of pentacene were grown using horizontal physical vapor-phase transport as described earlier [27], or in a closed ampoule under vacuum. The crystals were then structurally characterized using a laboratory Oxford Diffraction Xcalibur-2 charge-coupled device (CCD) diffractometer equipped with a Cryojet temperature-control system, and using synchrotron radiation on the Swiss-Norwegian beamline (SNBL) at the European Synchrotron Radiation Facility (ESRF) .…”

Section: Methodsmentioning

confidence: 99%

A Polymorph Lost and Found: The High‐Temperature Crystal Structure of Pentacene

Siegrist¹,

et al. 2007

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A well‐defined structural phase transformation is observed in bulk single crystals of pentacene, whereas pentacene powders heated above the phase‐transformation temperature do not always fully convert, and upon cooling, coexistence of the two polymorphs is observed down to room temperature. The first‐order phase transformation is isostructural: the close‐packed herringbone‐type layers shift against each other, keeping the same symmetry.

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Section: Methodsmentioning

confidence: 99%

A Polymorph Lost and Found: The High‐Temperature Crystal Structure of Pentacene

Siegrist¹,

et al. 2007

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“…3 The vapor phase growth of single organic crystals is traditionally performed by physical vapor transport (PVT) in process conditions close to thermodynamics equilibrium. 13 The growth of arrays of single pentacene crystals by PVT has been previously achieved using substrates with patterned self-assembled monolayers (SAM). 9 The nucleation of pentacene molecules was localized to the rough SAM films and resulted in growth of single crystals on areas of 5 µm x 5 µm.…”

Section: Introductionmentioning

confidence: 99%

Arrays of Pentacene Single Crystals by Stencil Evaporation

Fesenko

Flauraud

Xie

et al. 2016

Crystal Growth & Design

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In order to realize high-performance organic thin-film transistors (TFT), two parameters of the organic semiconducting layer are desired: single crystallinity for high mobility, and patterning for low off currents. High-quality single crystals can be fabricated using vapor techniques such as physical vapor transport (PVT) but they require high temperatures close to thermodynamic 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 equilibrium, for example, 240°C for pentacene. Such high temperatures are not ideal for TFT fabrication on plastic substrates and limit the use of PVT in flexible electronics applications.In this work arrays of pentacene single crystals were directly deposited at low temperature of 40°C by vacuum thermal evaporation through micro-fabricated stencil masks (stencil lithography). By decreasing the stencil aperture size down to 1 µm x 1 µm, we were able to limit the nucleation area until only one grain per aperture is nucleated and grown. We studied systematically scaling effects for large singe crystal growth and discuss details of the growth morphology. We found for instance that the formed pentacene crystals are one monolayer thick and the crystal area is much larger than the aperture size. This can be explained by the diffusion of adsorbed molecules on the surface laterally under the shadow mask, where they are protected from other impinging molecules. The diffusion away from the impinging area under the aperture affects the nucleation density inside this area and was used to calculate the diffusion length to nucleation λ N = 0.66 ± 0.11 µm of pentacene on SiO 2 at 40°C. Our diffusion-driven growth of organic single crystals by stencil lithography is a direct method to grow patterned arrays of single crystalline organic thin-film semiconductor layers.

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“…We propose a model of a deep acceptor state that explains the conductivity and PL characteristics. In addition, this study indicates that the oxygen-related state enhances the dissociation rate for tightly bound molecular excitons.Rubrene single crystals were grown by the vapor transport method [15] in a stream of pure hydrogen to prevent oxidation during crystal growth (the crystals were handled in air after the growth). Selected crystals were either deliberately oxidized in an oxygen atmosphere for 14 h at 100 C or placed in vacuum shortly after the growth.…”

mentioning

confidence: 99%

“…Rubrene single crystals were grown by the vapor transport method [15] in a stream of pure hydrogen to prevent oxidation during crystal growth (the crystals were handled in air after the growth). Selected crystals were either deliberately oxidized in an oxygen atmosphere for 14 h at 100 C or placed in vacuum shortly after the growth.…”

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confidence: 99%

Oxygen-Related Band Gap State in Single Crystal Rubrene

Mitrofanov¹,

Lang

Kloc³

et al. 2006

Phys. Rev. Lett.

115

113

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A molecular exciton signature is established and investigated under different ambient conditions in rubrene single crystals. An oxygen-related band gap state is found to form in the ambient atmosphere. This state acts as an acceptor center and assists in the fast dissociation of excitons, resulting in a higher dark and photoconductivity of oxidized rubrene. The band gap state produces a well-defined photoluminescence band at an energy 0.25 eV below the energy of the 0-0 molecular exciton transition. Twophoton excitation spectroscopy shows that the states are concentrated near the surface of naturally oxidized rubrene. DOI: 10.1103/PhysRevLett.97.166601 PACS numbers: 72.80.Le, 71.20.Rv, 71.35.ÿy Charge transport in organic molecular crystals is notably different from inorganic semiconductors. Despite a large number of investigations, understanding the fundamental processes governing charge transport remains a central issue for organic-based devices. In particular, the origin of band gap states and their effect on electronic and optical characteristics are both controversial and important questions [1,2]. Rubrene (C 42 H 28 ) in single crystal form has emerged as an important aromatic molecular solid, showing the highest field effect transistor (FET) mobility to date among organics (20 cm 2 =V s) [3]. In addition, several studies suggest that bandlike transport is operative [3][4][5][6]. Electronic properties in rubrene are, however, highly sensitive to both atmospheric environment as well as material treatment. As is true for inorganic semiconductors, device applications demand the understanding and control of such environmental factors, but the situation in rubrene is far from clear to date. Oxidation of organic crystals often results in modification of transport characteristics [7][8][9][10][11], and recent studies indicate that the presence of ambient oxygen also affects the conductivity of crystalline rubrene [12,13]. Furthermore, chemical analysis of naturally oxidized crystalline rubrene shows that the relative concentration of rubrene peroxide (C 42 H 28 O 2 ) can be as much as 1% at a depth of 50 nm [14], a length scale greater than a typical FET channel depth. Such a high impurity concentration will likely have a significant effect on charge transport, particularly if the impurity forms a band gap state.In this Letter, we demonstrate the formation of a band gap state in oxidized rubrene crystals and address the impact of the state on charge transport and exciton recombination. A spectral signature consistent with the molecular exciton model is established and investigated under different ambient conditions. A well-defined photoluminescence (PL) band at an energy lower than the highest exciton recombination transition energy develops in the spectra of oxidized rubrene. The PL band reflects an additional radiative recombination path through the oxygenrelated state in the band gap. The PL depth profile indicates that the oxygen-related band is emitted only from a surface region. Correlation between the ...

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Physical vapor growth of organic semiconductors

Cited by 628 publications

References 11 publications

A Polymorph Lost and Found: The High‐Temperature Crystal Structure of Pentacene

A Polymorph Lost and Found: The High‐Temperature Crystal Structure of Pentacene

Arrays of Pentacene Single Crystals by Stencil Evaporation

Oxygen-Related Band Gap State in Single Crystal Rubrene

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