Structure of a pentacene monolayer deposited on SiO2: Role of trapped interfacial water

Wo, Songtao; Wang, Binran; Zhou, Hua; Wang, Yiping; Bessette, Jonathan T.; Headrick, Randall L.; Mayer, Alex C.; Malliaras, George G.; Kazimirov, A.

doi:10.1063/1.2364565

Cited by 24 publications

(19 citation statements)

References 23 publications

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“…Specifically, we assume that the substrate is composed of a thin amorphous layer with density ρ 1 and thickness T 1 = cτ on an amorphous, semi-infinite layer with density ρ 0 . This model is particularly suitable for amorphous substrates such as SiO 2 , but also valid for Si substrates with a thin SiO 2 native oxide 29 , and thick, thermal SiO 2 layers covered by a self-assembled monolayer 20,30 or an interfacial water layer 16,31 .…”

Section: Theory a X-ray Scatteringmentioning

confidence: 99%

Quantitative modeling ofin situx-ray reflectivity during organic molecule thin film growth

2011

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Synchrotron-based x-ray reflectivity is increasingly employed as an in situ probe of surface morphology during thin film growth, but complete interpretation of the results requires modeling the growth process. Many models have been developed and employed for this purpose, yet no detailed, comparative studies of their scope and accuracy exists in the literature. Using experimental data obtained from hyperthermal deposition of pentane and diindenoperylene (DIP) on SiO2, we compare and contrast three such models, both with each other and with detailed characterization of the surface morphology using ex-situ atomic force microscopy (AFM). These two systems each exhibit particular phenomena of broader interest: pentacene/SiO2 exhibits a rapid transition from rough to smooth growth. DIP/SiO2, under the conditions employed here, exhibits growth rate acceleration due to a different sticking probability between the substrate and film. In general, independent of which model is used, we find good agreement between the surface morphology obtained from fits to the in situx-ray data with the actual morphology at early times. This agreement deteriorates at later time, once the root-mean squared (rms) film roughness exceeds about 1 ML. A second observation is that, because layer coverages are under-determined by the evolution of a single point on the reflectivity curve, we find that the best fits to reflectivity data -corresponding to the lowest values of χ 2 ν -do not necessarily yield the best agreement between simulated and measured surface morphologies. Instead, it appears critical that the model reproduce all local extrema in the data. In addition to showing that layer morphologies can be extracted from a minimal set of data, the methodology established here provides a basis for improving models of multilayer growth by comparison to real systems.

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Section: Theory a X-ray Scatteringmentioning

confidence: 99%

Quantitative modeling ofin situx-ray reflectivity during organic molecule thin film growth

2011

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“…Mayer and Headrick et al reported that a thin layer of water is trapped between an organic film and SiO 2 substrate even if the organic film is deposited under high vacuum condition, as long as no special surface treatment or annealing had been done prior to or during the evaporation process. [17,22] Water also condensed at exposed grain boundaries, which plays a substantial role in device performance. In our experiment, the substrates were kept at room temperature, and no surface treatment had been done.…”

mentioning

confidence: 99%

Monolayer‐Dimensional 5,5′‐Bis(4‐hexylphenyl)‐2,2′‐bithiophene Transistors and Chemically Responsive Heterostructures

2008

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The organic semiconductor 5,5′‐Bis(4‐ hexylphenyl)‐2,2′‐bithiophene (6PTTP6) shows a remarkable 2D growth mechanism. Without requiring a complicated fabrication process, organic field‐effect transistors (OFETs) with only a 1.5 monolayer 6PTTP6 film show mobilities close to those of conventional thick OFETs. Our heterostructured OFET blend exhibits a much faster response speed and a higher sensitivity to nerve‐agent simulants than thicker OFET analogues.

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“…Under these conditions, a monolayer coverage of the surfaces with adsorbed water may persist. 23 The deposition rate was monitored with a quartz crystal microbalance and equal to 0.3-0.5 Å min…”

Section: Film Preparationmentioning

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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Structure of a pentacene monolayer deposited on SiO2: Role of trapped interfacial water

Cited by 24 publications

References 23 publications

Quantitative modeling ofin situx-ray reflectivity during organic molecule thin film growth

Quantitative modeling ofin situx-ray reflectivity during organic molecule thin film growth

Monolayer‐Dimensional 5,5′‐Bis(4‐hexylphenyl)‐2,2′‐bithiophene Transistors and Chemically Responsive Heterostructures

Formation of intra-island grain boundaries in pentacene monolayers

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