LAUSR

We hereby report detailed structural and morphological studies for an ultrathin NiO/ZnO bilayer structure grown on sapphire (001) substrate using pulsed laser deposition technique. The combined X‐ray reflectivity (XRR) and grazing incidence X‐ray fluorescence (GIXRF) studies revealed formation of a low‐density defective ZnO interfacial layer of thickness ~32 Å at the ZnO/sapphire interface prior to growth of main ZnO layer. Our results further indicate that the variation of electron density across the NiO/ZnO bilayer structure is smooth and we do not observe presence of any interface layer between them. X‐ray diffraction measurements show that deposited ZnO layer is epitaxial in nature whereas NiO is highly oriented along (100) direction. The angle dependent X‐ray absorption near edge fine structure (XANES) measurements at Ni–K edge has been utilized to determine depth‐resolved oxidation state of Ni and the results have been correlated with the depth‐resolved electron density of NiO layer. The method described here offers nondestructive determination of the microstructural parameters as well as depth‐resolved mapping of oxidation state of a thin film‐based heterojunction device. It extends several advantages over destructive methods which are abundantly reported in literature.