Structural, magnetic and electronic properties of Zn0.94Co0.06O/ZnO heterostructure

In the present work, single layers of ZnO, Zn 0.94 Co 0.06 O and Zn 0.94 Co 0.06 O/ZnO heterostructure thin film on quartz substrates as well as on Si (111) substrate have been prepared using RF ion beam sputtering. Grazing incident X-ray diffraction (GIXRD), UV–Vis spectroscopy, X-ray absorption near edge structure (XANES), vibrating sample magnetometer (VSM) and photoelectron spectroscopy (PES) were performed to obtain structural, optical, electronic properties. GIXRD measurement confirms Wurtzite structure of ZnO, whereas UV–Vis spectroscopy shows a blue shift of the absorption edge in Zn 0.94 Co 0.06 O single layer with respect to ZnO film with band gap of 3.18 and 3.32 eV for ZnO and Zn 0.94 Co 0.06 O single layer films, respectively. The O K-edge spectra revealed O 2 p hybridization with Zn3 d 4 s /Co3 d states, whereas Co L 3 -edge and Co K-edge XANES spectra confirm Co 2+ oxidation state. M-H hysteresis measurement at 300 K shows a weak ferromagnetism for Zn 0.94 Co 0.06 O single layer and Zn 0.94 Co 0.06 O/ZnO heterostructure thin film. Furthermore, to obtain band offset of Zn 0.94 Co 0.06 O/ZnO heterostructure thin films, valance band maximum and core level peaks were measured using PES measurement. The offsets in valance band and conduction band for Zn 0.94 Co 0.06 O/ZnO heterostructure thin film were obtained as ~0.41 eV and ~0.55 eV, respectively, and compared with ~0.36 eV and ~0.51 eV, respectively, of Zn 0.9 Co 0.1 O/ZnO heterostructure thin films. The results show that a type-II band alignment in the studied system.