Influence of Ion Beam Irradiation on Optical and Magnetic Properties of Transparent Mn Doped ZnO Thin Films, Suitable for Sensor Applications

Abstract

The present work describes modification in physical properties of Zn0.95Mn0.05O films by ion beam irradiation. Films were prepared by spin coating and annealed at 500°C. XRD patterns of these films show wurzite structure with good crystalline quality. However, low-energy irradiation could modify and induce new defect states. Characterization of those defects had been performed by analyzing the UV-Visible absorption spectroscopy and photoluminescence (PL) spectroscopy. Room-temperature PL emission of Zn0.95Mn0.05O film shows a broad UV emission and pronounced visible emission ~530 nm. At low temperature, broad UV band become more prominent; however, it is completely quenched after irradiation. For all irradiated films we noted only visible emission of comparable intensities, confined within the region 475 to 550 nm. Irradiated films are showing ferromagnetism at room temperature and most importantly the film irradiated at fluence F: 1016 ions/cm2 exhibit maximum saturation magnetic moment of 0.83 emu g-1. The magnetic response is strongly influenced by irradiation and we could say that magnetism is strongly correlated with intrinsic defects present in these films. Defect-induced formation of bound magnetic polarons actually control the ferromagnetic property of these films. These transparent ferromagnetic films could be used in optoelectronics.

Physical property modifications with transition metal doping in nanostructured Zn1-xNixO (x = 0.03, 0.05); synthesized by chemical co-precipitation technique

“…It is important to note that c/a ratio for the doped and un-doped ZnO samples is smaller than 1.633 (the c/a ratio of ideal wurzite structure) [19]. It indicates structural distortion in wurzite structure in these synthesized samples [20]. However the c/a ratio in nearly constant for all these samples, possibly due to nearly same size of the Ni 2+ and Zn 2+ ions.…”

“…ZnO is a direct wide band-gap semiconductor. The optical band gap E g can be determined by Tauc relation [20].…”

“…In case of ZnO with the excitation wave-lengths: λ ex = 320 nm, the 1 st peak is observed is near 386 nm (3.21 eV) and that peak corresponds to near band edge (NBE) emission. The second peak is located around 410 nm (3.02 eV) is possibly due to transition between shallow donor level created by interstitials Zn I defects to the upper level of the valance band [20,21]. In case of Zn 0.93 Ni 0.07 O and Zn 0.93 Ni 0.07 O samples the near band edge emission was found at 393 nm and the defect related emission peak has been observed near 440 nm.…”