Structural and Electrostatic Complexity at a Pentacene/Insulator Interface

Puntambekar, Kanan P.; Dong, Jinsheng; Haugstad, Greg; Frisbie, C. Daniel

doi:10.1002/adfm.200500816

Cited by 145 publications

(164 citation statements)

References 41 publications

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“…The coalescence process seems not to influence the orientation alignment of merging islands (see arrows in Fig. 5(b)), in agreement with previous findings [27] so that a large number of grain boundaries is present in the first monolayer [33]. The second-layer islands, which cover about 1/5 of the monolayer, show a typical dendritic shape with a mean fractal dimension D f = 1.60 ± 0.06, 1 and most of them are composed of several crystalline domains.…”

Section: Resultssupporting

confidence: 81%

“…We also employed AFM to perform transverse shear microscopy (TSM) [25][26][27], where a silicon nitride tip (NP-20 Veeco Metrology and Instrument, USA) with a spring constant of 0.58 N m −1 is scanned in contact parallel to the cantilever's long axis. By mapping the variation in transverse shear force, we could qualitatively determine the crystallinity of a single molecular island or of the whole monolayer.…”

Section: Afm Characterizationmentioning

confidence: 99%

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Key role of molecular kinetic energy in early stages of pentacene island growth

Toccoli²,

Zhang

et al. 2009

Appl. Phys. A

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Organic molecular beam deposition is studied systematically at thermal and hyperthermal regimes aiming at investigating the role of molecular kinetic energy on the growth mechanism of pentacene submonolayers on SiO x /Si. We show that the kinetic energy of the impinging molecule (E k ) plays a crucial role in determining island structure and shape, distribution of island sizes, the crystalline quality of the first monolayer, and even the growth mode of subsequent layers. With increasing E k , the island structure changes from fractal to nonfractal, the shape becomes more anisotropic and the island size more uniform, pointing to correlated island growth. Moreover, while 3D island growth is observed for thermal organic molecular beam de- position, supersonic molecular beam deposition gives rise to layer-by-layer growth, at least for the first two layers. When E k ≥ 5.0 eV, the first monolayer is composed of large single crystalline domains which can extend over up to 10 μm, inferred from comparing atomic force micrographs of height and net transverse shear force. In these growth conditions both the high surface diffusivity and energy redistribution play a major role. We propose a mechanism where the energy dissipation occurring during the molecule-surface collision leads to the reorientation of whole islands during island coalescence, resulting in the elimination of grain boundaries.PACS 72.80.Le · 81.15-z · 79.20Rf · 68.37.Ps · 68.55.J · 34.25.+a

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Section: Resultssupporting

confidence: 81%

Section: Afm Characterizationmentioning

confidence: 99%

Key role of molecular kinetic energy in early stages of pentacene island growth

Toccoli²,

Zhang

et al. 2009

Appl. Phys. A

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“…It tracks the twisting of the cantilever due to the lateral forces acting perpendicular to the scan vector and can be used to visualise the relative orientation of grains in thin films with high contrast. 19,21,[35][36][37] Fig. 3 shows transverse shear for the different substrate preparations and pentacene deposition conditions, the molecular island count was averaged from five AFM images collected in different regions on each sample.…”

Section: Afm and Tsm Characterisation Of Pentacene Submonolayersmentioning

confidence: 99%

Formation of intra-island grain boundaries in pentacene monolayers

Zhang

Duhm

et al. 2011

Phys. Chem. Chem. Phys.

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To assess the formation of intra-island grain boundaries during the early stages of pentacene film growth, we studied sub-monolayers of pentacene on pristine silicon oxide and silicon oxide with high pinning centre density (induced by UV/O 3 treatment). We investigated the influence of the kinetic energy of the impinging molecules on the sub-monolayer growth by comparing organic molecular beam deposition (OMBD) and supersonic molecular beam deposition (SuMBD). For pentacene films fabricated by OMBD, higher pentacene island-density and higher polycrystalline island density were observed on UV/O 3 -treated silicon oxide as compared to pristine silicon oxide. Pentacene films deposited by SuMBD exhibited about one order of magnitude lower island-and polycrystalline island densities compared to OMBD, on both types of substrates. Our results suggest that polycrystalline growth of single islands on amorphous silicon oxide is facilitated by structural/chemical surface pinning centres, which act as nucleation centres for multiple grain formation in a single island. Furthermore, the overall lower intra-island grain boundary density in pentacene films fabricated by SuMBD reduces the number of charge carrier trapping sites specific to grain boundaries and should thus help achieving higher charge carrier mobilities, which are advantageous for their use in organic thin-film transistors.

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“…50 Finally, TSM has been combined with Kelvin-probe microscopy directly revealing localized surface-potential wells at the grain boundaries indicating that they are likely to serve as charge-carrier traps. 53 …”

Section: Transverse Shear Microscopymentioning

confidence: 99%

“…AFM has become a standard laboratory tool for the characterization of film topography with high resolution. However, as outlined [50][51][52][53][54] has demonstrated the ability to image domain orientation on the desired length scale using a conventional atomic force microscope. In this technique, the twist experienced by the cantilever as it is scanned is monitored via the lateral deflection of the laser beam, depicted schematically in Figure 9(a).…”

Section: Transverse Shear Microscopymentioning

confidence: 99%

Imaging the domain structure of organic semiconductor films

McNeill

2011

J Polym Sci B Polym Phys

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State-of-the-art solution-processed organic fieldeffect transistors typically use polycrystalline organic semiconductor thin films as the active layer. Although it is widely regarded that boundaries between polycrystalline domains are a likely source of charge trapping limiting charge carrier mobility, little is known about the detailed domain structure of such films. Furthermore, variations in local order particularly in conjugated polymer films are likely to further impede charge transport. In recent years a number of techniques have been exploited that are able to provide information regarding local domain orientation and molecular order in polycrystalline organic thin films. These techniques have provided new information regarding the nature of domain structure providing an opportunity to directly evaluate the influence of domain structure on device operation. This article aims to provide a timely review of the experimental approaches used to date and provide a perspective for future work.

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Structural and Electrostatic Complexity at a Pentacene/Insulator Interface

Cited by 145 publications

References 41 publications

Key role of molecular kinetic energy in early stages of pentacene island growth

Key role of molecular kinetic energy in early stages of pentacene island growth

Formation of intra-island grain boundaries in pentacene monolayers

Imaging the domain structure of organic semiconductor films

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