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Surface and interface properties of thin pentacene and parylene layers

100%

Vincze A., Jakabovič J., Srnánek R., Šatka A., Kovac J.

Open Physics

2009

vol. 7

issue 2

270-278

To improve Organic Thin Film Transistor (OTFT) properties we study OTFT semiconductor/dielectric interfacial properties via examination of the gate dielectric using thin Parylene C layer. Structural and morphology properties of pentacene layers deposited on parylene layer and SiO2/Si substrate structure were compared. The surface morphology was investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM topography of pentacene layer in non-contact mode confirmed the preferable pentacene grain formation on parylene surface in dependence on layer thickness. The distribution of chemical species on the surfaces and composition depth profiles were measured by secondary ion mass spectroscopy (SIMS) and surface imaging. The depth profiles of the analyzed structures show a homogenous pentacene layer, characterized with C or C2 ions. Relatively sharp interface between pentacene and parylene layers was estimated by characteristic increased intensity of CCl ions peak. For revealing the pentacene phases in the structures the Micro-Raman spectroscopy was utilized. Conformal coatings of parylene and pentacene layers without pinholes resulted from the deposition process as was confirmed by SIMS surface imaging. For the pentacene layers thicker than 20 nm, both thin and bulk pentacene phases were detected by Micro-Raman spectroscopy, while for the pentacene layer thickness of 5 and 10 nm the preferable thin phase was detected. The complete characterisation of pentacene layers deposited on SiO2 and parylene surface revealed that the formation of large grains suggests 3D pentacene growth at parylene layer with small voids between grains and more than one monolayer step growth. The results will be utilized for optimization of the deposition process.

PbS nanostructures synthesized via surfactant assisted mechanochemical route

86%

Baláž P., Pourghahramani P., Dutková E., Fabián M., Kováč J., Šatka A.

Open Chemistry

2009

vol. 7

issue 2

215-221

PbS nanocrystals using surfactant assisted mechanochemical route has been successfully prepared. The methods of XRD, SEM, surface area and particle size measurements were used for nanocrystals characterization. The XRD patterns confirmed the presence of galena PbS (JCPDS 5–592) whatever treatment conditions were applied. The strong observable peaks indicate the highly crystalline nature in formation of PbS nanostructures where preferential crystal growth in the (200) direction after chelating agent (EDTANa2•2H2O) addition has been observed. The mean volume weighted crystallite size 4.9 nm and 35 nm has been calculated from XRD data using Williamson-Hall method for PbS synthesized without and/or with chelating agent, respectively corresponding with surface weighted crystallites sizes of 2.9 and 18.8 nm. The sample prepared without surfactant yields the smaller crystallites and the higher microstrain compared with surfactant assisted synthesis. The obtained results illustrate a possibility to manipulate crystal morphology by combining effect of milling and surfactant application. [...]

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1 Open Chemistry

1 Open Physics

2 2009

2 Šatka A.

1 Baláž P.

1 Dutková E.

1 Fabián M.

1 Jakabovič J.

1 Kovac J.

1 Kováč J.

1 Pourghahramani P.

1 Srnánek R.

1 Vincze A.

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Surface and interface properties of thin pentacene and parylene layers

PbS nanostructures synthesized via surfactant assisted mechanochemical route