Evidence of Self-Affine Rough Interfaces in a Langmuir-Blodgett Film from X-Ray Reflectometry

A Langmuir-Blodgett multilayer film of tricosenoic acid with a cadmium-substituted headgroup has been studied by x-ray reflectometry. The diffuse or off-specular scattering close to the positions of the 20 observed Bragg peaks in the reflectivity profile has been studied. Its line shape has been found to be Lorentzian and the half-widths of the peaks vary according to the square of the longitunal wave vector $q_z$. This suggests that the film is characterized by self-affine rough interfaces, with no cutoff length, corresponding to a roughness texture $h=0.5\mathrm{}$.