Investigations on the structural, optical and electronic properties of Nd doped ZnO thin films

Abstract

We report the synthesis and characterization of Nd doped ZnO thin films grown on Si (1 0 0) substrates by the spray pyrolysis method. The surface morphology of these thin films was investigated by scanning electron microscopy and shows the presence of randomly distributed structures of nanorods. Grazing angle x-ray diffraction studies confirm that the doped Nd ions occupied Zn sites and these samples exhibited a wurtzite hexagonal-like crystal structure similar to that of the parent compound, ZnO. The micro-photoluminescence measurement shows a decrease in the near band edge position with Nd doping in the ZnO matrix due to the impurity levels. The near-edge x-ray absorption fine structure (NEXAFS) measurements at the O K edge clearly exhibit a pre-edge spectral feature which evolves with Nd doping, suggesting incorporation of more charge carriers in the ZnO system and the presence of strong hybridization between O 2p–Nd 5d orbitals. The Nd M5 edge NEXAFS spectra reveal that the Nd ions are in the trivalent state.

Transparent conductive Nd-doped ZnO thin films

“…In the same way the full width at half maximum (FWHM) of (0 0 2) rocking curves are significantly larger than the ones measured on undoped films, Nd can be incorporated by substitution of Zn or in an interstitial position in the wurtzite ZnO lattice. Results from the NEXAFS study show strong evidence for hybridization of Nd ions with O in the ZnO lattice [15]. This study also indicates that trivalent Nd ions occupy divalent Zn sites.…”

“…The direct excitation of Nd 3+ ions in the ZnO matrix was possible, and an intense signal was also observed when the ZnO host was excited by UV light. This demonstrates the existence of a transfer mechanism between the ZnO host and Nd 3+ ions [15,19], i.e. Nd-doped ZnO films could act as an efficient downshifter in PV devices [19].…”

“…More specifically, the effects of incorporation of Nd 3+ ions on the structure, microstructure, and chemical nature of Nd-doped ZnO thin films were investigated [15][16][17]. For limited Nd-doping concentration (a few %), the hexagonal ZnO wurtzite structure with a preferential orientation (c-axis texture) is preserved with a variation of the c-axis parameter because of the difference in ionic radii of Nd 3+ and Zn 2+ .…”

“…For limited Nd-doping concentration (a few %), the hexagonal ZnO wurtzite structure with a preferential orientation (c-axis texture) is preserved with a variation of the c-axis parameter because of the difference in ionic radii of Nd 3+ and Zn 2+ . In addition, x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) measurements reveal that Nd species are in the trivalent state and occupy Zn site in the network [15,16]. Such Nd-doped ZnO films were highly transparent in the visible wavelength domain, and the energy bandgap was found to depend not only on the Nd doping level but also on the deposition process and conditions [10,18].…”

“…Such Nd-doped ZnO films were highly transparent in the visible wavelength domain, and the energy bandgap was found to depend not only on the Nd doping level but also on the deposition process and conditions [10,18]. The luminescence properties of Nd 3+ ions in ZnO were studied [15,19], and intense luminescence indicating infrared emission of Nd 3+ in ZnO was observed. The direct excitation of Nd 3+ ions in the ZnO matrix was possible, and an intense signal was also observed when the ZnO host was excited by UV light.…”