Observation of Three Growth Mechanisms in Self-Assembled Monolayers

Time-resolved atomic force microscopy and contact angle measurements reveal that the self-assembly of octadecyltrichlorosilane-based monolayers on the oxidized Si(100) surface can be initiated by three distinct mechanisms: island growth at low temperatures ( T < 16 °C), homogeneous growth at high temperatures ( T ≥ 40 °C), and a mixed regime at intermediate temperatures. These results support the notion of a transient Langmuir film at the substrate−solution interface: the observed growth patterns are consistent with nucleation of liquid-condensed domains coexisting with a two-dimensional gas at low temperature, or with a liquid-expanded phase at intermediate temperatures.