Self-assembled" monolayers of amphiphilic surfactant molecules form spontaneously on solid surfaces by exposure to dilute solutions of the adsorbate molecules. These monolayers are shown to form via a mechanism that includes nucleation, growth, colalescence, etc. of denselypacked submonolayer islands ofthe long-chain organic molecules. In situ atomic force microscopy experiments allow a quantitative analysis of island nucleation and growth rates as well as determination of the island size distribution oas a function of coverage. In the growth regime, the nucleation and growth rates have a power law behavior consistent with a simple point island model of 2D cluster growth. The exponents are consistent with a critical nucleus of two molecules and the 2D diffusion coefficient corresponds to a "hopping time" of about 1 microsecond. In the aggregation regime, the island size distributions are shown to scale with a single evolving length scale in accordance with the dynamical scaling approxiamtion.
展开▼
