Domain boundaries and buckling superstructures in Langmuir-Blodgett films

• Published in: Nature (London) 1992-05, Vol.357 (6373), p.54-57
• Main Authors: Garnaes, J, Schwartz, D. K, Viswanathan, R, Zasadzinski, J. A. N
• Format: Article
• Language: English
• Subjects: Boundaries; Chemistry; Exact sciences and technology; General and physical chemistry; Humanities and Social Sciences; letter; Molecules; multidisciplinary; Science; Science (multidisciplinary); Solid-liquid interface; Surface physical chemistry; Weights & measures
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/357054a0

MANY technological and scientific applications have been proposed for Langmuir–Blodgett (LB) films 1 . These ordered arrays of oriented amphiphilic molecules may be useful as nonlinear optical systems 2 , as insulating or patterning layers in microelectronics 3,4 , as model systems for studies of two-dimensional phases 5 and as molecular templates for protein crystallization 6 . The potential of LB films for these applications is sensitive to the details of their molecular packing; in particular, they require that the layers have a defect-free, periodic structure 1 . Here we present images from atomic force microscopy of domain boundaries between regions of different crystallographic orientation in LB multilayers. The regular lattice structure is preserved to within 1 nm of the grain boundaries, and the domains are oriented in a near-twinning arrangement. We also observe a periodic buckling superstructure along a particular lattice symmetry direction, with a wavelength of about 2 nm and an amplitude of ≤0.1 nm. The buckling was independent of surface pressure during deposition, dipping direction, number of layers deposited and nature of the substrate, and was stable over many hours. These departures from two-dimensional periodicity may have an important bearing on applications that rely on perfect crystallinity.