Observation and analysis of spectral interference modulations in thin film light scattering experiments using synchrotron radiation

Light scattering in thin films represents several essential microstructural, morphological and compositional parameters in thin film systems. Under the present investigation certain gadolinia, silica thin films and multilayer systems have been probed for their spectral scattering signals using the photophysics beamline of INDUS-1 synchrotron radiation source. The pulsed structure of synchrotron radiation and its interaction with certain non-wedge optical component has however led to the spectral interference (SI) modulations in scattering signals, which was tackled by an appropriate modelling and analysis technique. Under this technique the geometric mean of the SI amplitudes were computed and then de-convoluted into several Gaussian peaks. Each Gaussian peak was made to interfere with an appropriate temporally delayed peak having certain transformed amplitude factors. Superposition of all these Gaussian interference was computed and compared with the experimental profile in an iterative manner to determine the mean pulse delay introduced by the optical element. Finally the inverse fast Fourier transform of the experimental SI signal was carried out to compare the modelling results and both the approaches demonstrated a closed match. Spectral scattering signals recorded for various thin film layer combinations depicted close resemblances with the specular characteristics recorded using a spectrophotometric technique. This distinctly highlights the dominance of multilayer thin film interference phenomena on the spectral light scattering characteristics.