A study of the transition from Y- to X-type transfer during deposition of lead stearate and cadmium stearate langmuir-blodgett films

We have continuously monitored both the capillary force exerted on the substrate and the transfer ratio during Langmuir-Blodgett (LB) deposition of lead stearate and cadmium stearate. At first, when deposition is Y-type, the capillary force (thus, the contact angle) and transfer ratio are uniform over the dipping stroke. Later, the contact angle becomes larger on the upstroke while the transfer ratio drops (i.e., tends toward X-type); the changes are not uniform, however, but occur first near the bottom of the substrate. The onset of these changes can be delayed by increasing the dipping speed or the ion concentration in the subphase. Scanning electron micrographs show Y-type films to be uniformly smooth, while X-type films show greater inhomogeneities near the bottom of the film than near the top.