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Experiments and theory on pentacene in the thin film phase: structural, electronic, transport properties, and gas response to oxygen, nitrogen, and ambient air (Articolo in rivista)

Type

Articolo in rivista (Classe)
Prodotto della ricerca (Classe)

Label

Experiments and theory on pentacene in the thin film phase: structural, electronic, transport properties, and gas response to oxygen, nitrogen, and ambient air (Articolo in rivista) (literal)

Anno

2007-01-01T00:00:00+01:00 (literal)

Alternative label

Parisse, P; Picozzi, S; Passacantando, M; Ottaviano, L (2007)
Experiments and theory on pentacene in the thin film phase: structural, electronic, transport properties, and gas response to oxygen, nitrogen, and ambient air
in Thin solid films (Print)
(literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori

Parisse, P; Picozzi, S; Passacantando, M; Ottaviano, L (literal)

Pagina inizio

8316 (literal)

Pagina fine

8321 (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume

515 (literal)

Rivista

Thin solid films (Rivista)

Note

ISI Web of Science (WOS) (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni

Univ Aquila, INFM, CNR, I-67010 Coppito, Italy; Univ Aquila, Dipartimento Fis, I-67010 Coppito, Italy (literal)

Titolo

Experiments and theory on pentacene in the thin film phase: structural, electronic, transport properties, and gas response to oxygen, nitrogen, and ambient air (literal)

Abstract

We investigated the morphological, structural, electronic, and transport properties of pentacene thin films grown by vacuum thermal evaporation on different inert substrates at room temperature. The results of our atomic force microscopy (AFM), X-ray diffraction and scanning tunnelling microscopy (STM) analysis show a structure in the so called 'thin film phase' with 1-2 gm sized gains. Atomic terraces are clearly evidenced with AFM and give an inter-planar spacing of 1.54 nm corresponding to the (001) distance. The Scanning Tunneling Spectroscopy measurements show an HOMO-LUMO gap of 2.2 eV. After vacuum thermal evaporation on patterned substrates with different inter-electrodes distances, we have performed in situ measurements of the electrical response of such thin films. We found for these films a resistivity of p=4.7 +/- 0.2 center dot 104 Omega in, that is an order of magnitude lower than the value reported to date in literature for single crystals of pentacene. This value is not affected by the presence of grain boundaries. The resistivity is further reduced by a factor 8.9 +/- 0.7 , 14 +/- 1, 2.3 +/- 0.3 upon exposure to oxygen, nitrogen and ambient air, respectively. In addition density functional theory calculations have been performed to investigate the electronic structure of pentacene in this specific phase, focusing on the effects on the relevant electronic properties of the relative orientation of the molecules within the crystalline unit cell, so far experimentally unknown. Our results show that the energy bandwidth and band-gap are crucially affected by the molecular stacking. Furthermore, by comparing our theoretical spectra with the scanning tunneling spectroscopy (STS) measurements, we propose a molecular arrangement that gives a good agreement with experiments as far as the relevant orbitals are concerned. For this polymorph, we find a HOMO and LUMO bandwidth of approximate to: 0.7 eV and approximate to 0.8 eV, respectively, which are significantly larger than those obtained for the pentacene bulk-phase and are consistent with the larger conductivity experimentally observed in pentacene thin films. (C) 2007 Elsevier B.V. All rights reserved. (literal)

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