Determination of small fluctuations in electron density profiles of thin films: Layer formation in a polystyrene film

A spin-coated thin polystyrene film on a silicon single crystal has been studied using the X-ray reflectivity technique. Signature of layering as a function of depth, due to confinement, in this polystyrene film could be detected from the reflectivity profile using a new analysis scheme. Small variations of electron density across the depth of a thin film can be determined from reflectivity data using this scheme with no a priori distribution of electron density profile.