Challenges in porosity characterization of thin films: Cross-evaluation of different techniques

Abstract

The review article provides an overview of the most important and popular techniques for evaluating the porosity of thin films developed for various applications. These methods include ellipsometric porosimetry (EP), positron annihilation (lifetime) spectroscopy (PAS/PALS), and grazing incidence small-angle x-ray scattering (GISAXS). Special attention is given to the challenges associated with interpreting the measured data and the inherent limitations of each method. It is demonstrated that EP, GISAXS, and PALS are all informative for studying the pore structure in thin films, with each method offering unique insights. GISAXS, in particular, allows for the evaluation of three-dimensional mesostructures, including pore arrangement, pore spacing, and structural order. On the other hand, PALS has a unique advantage in its capability to analyze extremely small isolated pores (free volume). The advantage of EP lies in its simplicity and the possibility to analyze multiple properties from the same set of measurements. The cross-evaluation of different methods offers important insights into the complex pore structure of materials, highlighting the significance of appropriate modeling and interpretation of data.