Improvement of Langmuir-Blodgett film structure by dynamic surface pressure control

Abstract

Conventional deposition procedures are carried out under the customary but uncertain assumption that the surface pressure over the whole surface always remains constant and coincides with that of a Wilhelmy plate monitor. In this study we directly evaluated the static (π sub, s) and dynamic (π sub, d) surface pressures at the substrate prior to and during substrate dipping respectively, by measuring the interface tension applied on the substrate. As a result, for viscous monolayers there appeared a stationary difference (Δπ) between π sub, s and π sub, d during the dipping. The magnitude of Δπ was found to depend strongly on monolayer viscosity, substrate-dipping speed, trough area and compression method. In the improvement of multilayer structure, a reduction of Δπ was found to be crucial. In order to regulate the dynamic surface pressure more precisely, we evolved a novel method which restrains monolayer flow and controls meniscus movement. This method was found to be effective in the improvement of film structure.