Dynamics of roughening and growth kinetics of CdS–polyaniline thin films synthesized by the Langmuir–Blodgett technique

Abstract

Thin films of cadmium sulphide (CdS) nanoparticle induced polyaniline (PANI) nanocomposites have worked as a better system for application in photovoltaics due to the efficient charge separation and charge transfer. In this communication, we have chosen such a system of varying thickness deposited by the Langmuir–Blodgett (LB) technique in order to study the growth and roughness phenomena by dynamic scaling theory. Different techniques such as X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and X-ray reflectivity (XRR) are used for characterization of these films. In the study, the growth exponent, β, is found to have a correlation with the invariant logarithmic scaling law. A very large value of β = 1.18 ± 0.23 as calculated is a result of the rapid roughening in the multilayer film growth process. We have investigated the dynamic scaling behavior of the multilayer system which shows a difference in the value of the coarsening factor and this confirms the breakdown of self-affinity as a consequence of some nonlocal growth effects. The normal grain formation with deposition at the initial stage and the increase in grain abnormality with increase in thickness is also verified in support of the dynamic scaling ansatz. In the present study the layer-by layer deposition is confirmed by XRR fitting for a 3 layer film whereas the multilayer shows diffusing behavior due to H-bonding or electrostatic interactions.