Morphology and structural evolution in cobalt stearate Langmuir-Blodgett films.

Structural evolution of cobalt stearate (CoSt) Langmuir-Blodgett (LB) films show 2D layer-by-layer or Frank van der Merwe type growth, with in-plane defect-free morphology and bidentate bridging metal ion headgroup coordination, as observed from both Atomic Force Microscopy (AFM) and X-ray Reflectivity (XRR) studies. Difference in headgroup structure of first monolayer with that of subsequent bilayers is observed from XRR studies. However, AFM study of preformed cobalt stearate (CoStp) LB films did not show such defect-free growth in spite of having same metal ion coordination, as seen from its bulk Fourier Transform Infra-red (FTIR) spectra. Increased interaction between two methyl groups of adjacent hydrocarbon tails in case of CoSt deposition was indicated from the observed lengthening of C-H bonds in these. Along with metal ion headgroup coordination, supramolecular tail-tail interaction is proposed to play a key role in defect free multilayer formation.