A comparative atomic force microscopic study of liquid crystal films: transferred freely-suspended vs. Langmuir-Blodgett : morphology, lattice, and manipulation

The atomic force microscope (AFM) provides direct structural information on transferred freely-suspended films of liquid crystals, ranging from morphology on the ``large. scale of micrometers down to intermolecular spacing on the angstrom scale. Multilayer film thickness is measured, as well as monolayer step heights and unit cell parameters. We show here that these values for film thickness, step heights, and intermolecular spacing are often in good agreement with electron diffraction and X-ray reflectivity measurements. However, in some cases the AFM data reveal previously undetected lattices and defects. AFM measurements are also performed on Langmuir-Blodgett (LB) films of the same class of molecules, allowing comparison of the different film-forming techniques. The AFM has also been used as a tool to intentionally deform the films, creating features of tailored dimensions. The forces required to deform the films are discussed.