Characterization techniques: (A) XPS (X-ray photoelectron spectroscopy): Hydrothermally deposited epitaxial thin films are characterized by XPS to retrieve useful information like composition, chemical structure and local arrangement of atoms that make up few layers of surface of film and also the interfacial layer between the film and substrate.X-ray photoelectron spectroscopy (XPS) was developed in the mid 1960s by Kai Siegnahm and his research group at the University of Uppsala, Swed
