Scanning optical microscopy of Langmuir-Blodgett films

Abstract In this research a scanning optical microscope has been used to obtain high quality images of Langmuir-Blodgett films. The system has been characterised using simple materials such as behenic acid, and step structures with heights corresponding to a molecular bilayer have been studied. Differential phase contrast imaging has been used to image these steps very clearly and to assess film quality. Resolution can be improved by using a confocal system, but the differences in intensity obtained across such steps are very small. This can be significantly improved by depositing the film onto a calculated thickness of thermally grown oxide on a silicon substrate. By considering the interference effects which occur within this system, the intensities produced across such a step have been modelled. When these are fitted to experimental results for a number of bilayers, the thickness and permittivity of behenic acid (2.7±0.2 nm and 2.4±0.1 respectively) were found to be in close agreement with other techniques.