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Determination of Crystallite Size and Lattice Strain in Hexaphenyl Thin Films by Line Profile Analysis

Published online by Cambridge University Press:  10 February 2011

H.-J. Brandt ,
R. Resel ,
J. Keckes ,
B. Koppelhuber-Bitschnau ,
N. Koch  and
G. Leising
H.-J. Brandt
Affiliation:
Institute for Solid State Physics, Technical University Graz, AUSTRIA
R. Resel
Affiliation:
Institute for Solid State Physics, Technical University Graz, AUSTRIA
J. Keckes
Affiliation:
Department of Theoretical Chemistry, Institute of Inorganic Chemistry, Slovak Academy of Sciences, Bratislava, SLOVAKIA and Erich Schmid Institute, Austrian Academy of Sciences, Leoben, AUSTRIA
B. Koppelhuber-Bitschnau
Affiliation:
Institute for Physical and Theoretical Chemistry, Technical University Graz, AUSTRIA
N. Koch
Affiliation:
Institute for Solid State Physics, Technical University Graz, AUSTRIA
G. Leising
Affiliation:
Institute for Solid State Physics, Technical University Graz, AUSTRIA
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Abstract

Hexaphenyl thin films (HTF) are widely used as an electro-active organic medium in blue light emitting diodes. The optical parameters of the HTF-based devices significantly depend on their microstructural properties.

HTF of different types are produced by physical vapor deposition on glass substrates applying specific sample preparation conditions. The microstructural properties of HTF are characterized using X-ray diffraction line profile analysis and atomic force microscopy (AFM). Diffraction peaks representing three different types of preferred growth in HTF are analyzed, namely textures with (00λ), (223) and (203) net planes oriented parallel to the substrate. No additional line-broadening (compared to silicon powder used as standard) is observed in the case of a film prepared at high substrate temperature of 170 °C. On the other hand, considerable broadening is detected in a film with the substrate kept at room temperature. Multiple line analysis documents that the crystallite size and lattice strain for the sample is 150 nm and 3×10−4, respectively. Single line analysis performed on the other reflections reveal size-induced broadening for a crystallite size in the range 40 to 50 nm. From AFM data we obtained that the maximum roughness of the surface is about 40 nm. The results indicate that the deposition temperature significantly influences the microstructural properties and that higher substrate temperature promotes a higher mobility of the molecules on the substrate enabling growth of larger crystallites with lower strain.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 561: Symposium F – Organic Nonlinear Optical Materials and Devices , 1999 , 161
Copyright
Copyright © Materials Research Society 1999

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References

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