I am interested to measure the porosity of thin films, what is the best technique for measuring porosity of thin films and what are the limitations of that specific technique?
"Porosity and its measurement" by Laura Espinal Characterization of Materials, edited by Elton N. Kaufmann John Wiley & Sons (2012), which you can find at the link: https://ws680.nist.gov/publication/get_pdf.cfm?pub_id=910393
and the "Porosity" document, in particular the part called "Porosity testing", source: https://m.tau.ac.il/~chemlaba/Files/Electrodeposition/13208_08.pdf
can give you useful information regarding your question.
The "best technique" for measuring porosity of thin films is also related to the specific features of the system you want to analyze.