X-ray reflectivity analysis of thin complex Langmuir-Blodgett films

@article{630745,
   author = {Polouček, Pavel and Pietsch, U. and Geue, T. and Symietz, C. and Brezesinski, G.},
   article_location = {Bristol, England},
   article_number = {4},
   keywords = {x-ray reflectivity; xrr; thin film; langmuir-blodgett films; density},
   language = {eng},
   issn = {0022-3727},
   journal = {Journal of physics D: Applied physics},
   title = {X-ray reflectivity analysis of thin complex Langmuir-Blodgett films},
   volume = {34},
   year = {2001}
}

TY  - JOUR
ID  - 630745
AU  - Polouček, Pavel - Pietsch, U. - Geue, T. - Symietz, C. - Brezesinski, G.
PY  - 2001
TI  - X-ray reflectivity analysis of thin complex Langmuir-Blodgett films
JF  - Journal of physics D: Applied physics
VL  - 34
IS  - 4
SP  - 450-458
EP  - 450-458
PB  - IOP Publishing Ltd.
SN  - 00223727
KW  - x-ray reflectivity
KW  - xrr
KW  - thin film
KW  - langmuir-blodgett films
KW  - density
N2  - Using specular x ray reflectivity, we have examined the vertical structure of charge coupled polyelectrolyte (PDADMAC)-lipid (DPPA) films on the water surface and on a silicon substrate, prepared by means of the Langmuir-Blodgett technique. The complicated structure of these films, characterized by electron density variations on the sub nanometre scale and low density contrast between sub layers, causes failure of the standard box model fitting method-it yields poor matching to data and/or ambiguous density profiles. We show that this problem can be overcome utilizing a different, model free fitting method, which yields perfect fits and less ambiguous electron density profiles for all investigated films. The ambiguity of results can be further reduced when the sets of possible density profiles obtained for several similar samples are compared to each other. Discussing the model free fitting method in detail along with general questions of reflectivity data evaluation, we aim to give practical instructions for the structure analysis of thin organic films. The obtained density profiles, being in good agreement with the structure model based on previous diffraction experiments, reveal some new details: The DPPA's phosphate head groups penetrate inside the PDADMAC helix rather than being bound onto its surface. The structure remains almost unchanged after transferring one layer onto Si wafer, but subsequently transferred layers exhibit decreasing order.
ER  - 

POLOUČEK, Pavel, U. PIETSCH, T. GEUE, C. SYMIETZ a G. BREZESINSKI. X-ray reflectivity analysis of thin complex Langmuir-Blodgett films. \textit{Journal of physics D: Applied physics}. Bristol, England: IOP Publishing Ltd., 2001, roč.~34, č.~4, s.~450-458. ISSN~0022-3727.