Atomic force microscope observation of nano-ordered undulation structure formed by bent-shaped molecules

The layer undulation, one of the frustration modes, in the X1 phase formed from the 4-bromo-1,3-benzene-bis[4-(4-alkoxyphenyliminomethyl)benzoate] was analyzed by Atomic force microscope (AFM) method. The AFM image shows a clear evidence of undulated layer structure in the homeotropically aligned sample. The layer undulation is observed as a mild sinusoidal wave with the periodic distance of 16-18 nm and the amplitude of 2-3 nm. Further, the undulation occurs in a random direction along the smectic layer, showing that the undulation direction is not related to the polar axis in the preceding B2 phase.