Study of 2D microstructure of ultrathin PEG-DMPE / DMPC film on solid substrates using AFM

Abstract

The 2-dimenional microstructure of a ultrathin film of DMPC and PEG-DMPE mixtures has been studied by using Atomic Force Microscope(: AFM). The composition of the binary mixture is a parameter to classify the films in terms of the fractal dimension, volume and mean height, and the characteristic pattern size. Films were prepared with a Langmuir-Blodgett(LB) technique and a spincoating technique. The topographic images show both quasi-circular and finger-like patterns. The 2D Fourier Transform analysis was used to find the characteristic wave vector of the patterns. The results show the ring shape, which indicates the similarity with a spinodal decomposition in a phase separation. Furthermore, the characteristic size $1/k_m$ was determined from the power spectral density corresponding to the radial part of 2D Fourier Transform of the AFM height profiles.