In the XPS spectra the binding energies of different species/ different valence states are separated and you can identify them and determine the samples stoichiometry.
Agreed with Daniela gogova. First you do XPS, for the elemental analysis and oxidation state of oxygen in ZnO. next for the oxygen intersitial defects Photoluminesence spectroscopy is a useful tool. As for the ZnO, we usually got the broad band in the visible region of the emission spectrum which is also known as the green emission related to oxygen vacancies. or please follow this paper. it would be helpful for you
I have one reference paper and I am attaching my data file. Can you please suggest me, the binding energy range of oxygen vacencies and oxygen interstials. I am able to interpet oxygen vacancy defects but not oxygen interstials.