PATTERN-FORMATION IN A SUBSTRATE-INDUCED PHASE-TRANSITION DURING LANGMUIR-BLODGETT TRANSFER

An atomic force microscope study of Langmuir-Blodgett films deposited from the liquid expanded phase was undertaken to explore self-organizi ng methods of creating patterned surfaces. Although tetradecanoic (TDA ), pentadecanoic (PDA), and hexadecanoic acid (HDA) monolayers deposit ed on silicon oxide at pH 5.8 are uniform flat films, when the same mo nolayers are deposited on silicon oxide at pH = 9.3 or on mica substra tes, the molecules organize into close-packed ''islands'', indicative of a two-dimensional condensation. The substrate dependence of this is landing behavior suggests that surface charge plays an important role. Small islands have compact morphology, while large islands are dendri tic. The length scale for the fingering instability changes by 2 order s of magnitude between TDA and HDA, from 60 nm to 6 mu m.