ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Langmuir–Blodgett films of various layer numbers of behenic acid on SiO2 surfaces were investigated by x-ray reflectivity before and after thermal treatment (annealing). The thicknesses of the monolayers at the substrate/film interface indicate that the molecules are oriented normal to the interface. For samples without further treatment, at some distance from the interface, three different layer spacings are found which correspond to molecular tilt angles of 21, 28, and 36 deg. The transition region of decreasing layer spacings extends roughly over the first five layers. The films are not in equilibrium after deposition. Their molecular packing and topology can be altered irreversibly by thermal treatment (annealing) at temperatures well below the main phase transition into an isotropic phase. Whereas the molecular ordering of the first monolayer is hardly affected by the heating, all other layer spacings are uniform after the heating, with molecular tilts of 36 deg. In the case of thick multilayers the thermally induced restructuring is accompanied by an increase of the total layer number due to the reduced layer spacing and material conservation. Thin multilayers breakup into multilayer islands and monolayer-covered substrate surface (dewetting). © 1996 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.471491
