Defect-mediated ferromagnetism in ZnO:Mn nanorods

In this work, the structural, chemical and magnetic properties of ZnO:Mn nanorods were investigated. Firstly, well-aligned ZnO nanorods with their long axis parallel to the crystalline c-axis were successfully grown by the vapor phase transport technique on Si substrates coated with a ZnO buffer layer. Mn metal was then diffused into these nanorods at different temperatures in vacuum. From SEM results, ZnO:Mn nanorods were observed to have diameters of ~100 nm and lengths of 4 µm. XPS analysis showed that the Mn dopant substituted into the ZnO matrix with a valence state of +2. Magnetic measurements performed at room temperature revealed that undoped ZnO nanorods exhibit ferromagnetic behavior which may be related to oxygen vacancy defect-mediated d0 ferromagnetism. ZnO:Mn samples were seen to show an excess room temperature ferromagnetism that is attributed to the presence of oxygen vacancy defects forming bound magnetic polarons involving Mn

INFLUENCE OF DEPOSITION TIME ON ELECTRODEPOSITED NICKEL SELENIDE (NiSe2) THIN FILMS FOR SOLAR/PHOTOELECTROCHEMICAL CELLS

The present study investigates the role of deposition time on the structural, morphological, compositional, optical and semiconducting properties of electrodeposited NiSe2 thin films. Nickel Selenide (NiSe2) is a transition metal chalcogenide material suitable for its good chemical and optical properties. The films were deposited on Indium Tin Oxide (ITO) coated conducting glass substrates at deposition times between 10 – 30 minutes with the interval of 5 minutes. The structural analysis of the films reveals the polycrystalline nature with sharp and high intense peaks. Scanning electron micrographs (SEM) reveals that grains are in spherical shape, uniform and pin-hole free. Composition analyses through energy dispersive X-ray (EDX) studies confirm the presence of Se and Ni to its stoichiometry.  The observed direct bandgap films reduced their energy gap values from 1.30 to 1.15 eV as the deposition time increases found by optical studies. Heat treatment of these films is annealed at 200◦C for 1 hour yield the high crystallinity that also confirms by X-ray diffraction. Annealed films with longer deposition time of 30 minutes shown cracks in the surface observed by SEM. The energy gap reduced in 20% for the annealed films. This investigation confirms that the deposition time has greater influences for the grown films.