Orientation of arachidate chains in Langmuir-Blodgett monolayers on Si(111)

The near-edge x-ray-absorption fine-structure technique is used to determine the orientation of cadmium- and calcium-arachidate chains on Si(111) at monolayer coverage. In our films the Cd-arachidate chain is found to be aligned along the surface normal and Ca arachidate is tilted by 33°±5°relative to Cd arachidate. The results are explained in terms of the surface bonding geometry of the terminal carboxylate group and the lateral interlocking of the zig-zag chains. © 1987 The American Physical Society.