NEUTRON AND X-RAY REFLECTOMETRY STUDIES OF ROUGH INTERFACES IN A LANGMUIR-BLODGETT-FILM

Neutron and X-ray reflectometry are used to study interlayer roughness and islanding in a 20-bilayer barium stearate Langmuir-Blodgett film with alternating hydrogenated and deuterated bilayers. The interlayer roughness is highly conformal, and analysis of the diffuse X-ray peak widths suggests it is approximately self-affine with a roughness expon ent of h approximate to 0.82. This roughness exponent describes the fi lm in all directions, even though steps on the substrate interrupt the correlation of the film across the steps. The neutron and X-ray specu lar reflectivities contain modulated Kiessig fringes, indicating the p resence of islands on the top of the film. Odd Bragg peaks in the neut ron specular reflectivity are broadened, implying long-range disorder in the H-D bilayer structure. These data suggest that the islands aros e from incomplete coverage during the film preparation. (C) 1998 Elsev ier Science B.V. All rights reserved.