Cleavage and Intercalation Properties of a Layered Compound, K4Nb6O17·3H2O, Studied with Atomic Force Microscopy

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Abstract
The surface structures of the title compound were studied with atomic force microscopy (AFM) after cleavage in air and after substitution of K+ with (CH3)4N+ (tetramethyl ammonium ion: TMA). Of the two interlayers, hydrated and anhydrated, cleavage in air occurred at the former when weak force was applied. Upon ion exchange at the hydrated interlayer with an aqueous solution of TMA, the niobate bilayer sheets broke free and slid against each other. The free bilayer sheets were mechanically weak enough to be scraped away by the stylus during scanning in the AFM measurement, which suggests the possibility of micromachining this material. Atom-resolved AFM images correspond to a regular arrangement of TMA with the methyl groups pointing in the directions of the crystal axes. This material can be used in constructing a two-dimensional assembly of organic molecules.