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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.

Thin films of cadmium doped zinc oxide (Cd : ZnO) with different cadmium concentrations have been prepared by the spray pyrolysis method on different substrates at 400 °C. The physical properties of the films were studied as a function of increasing cadmium dopant concentration (up to 25 wt%). The films were characterized by different methods to understand their structural, optical and electrical properties. Energy dispersive x-ray diffraction spectroscopy analysis showed that the Cd concentration in the solid film is slightly lower than that of the starting solution. The x-ray diffraction analysis revealed that the films are polycrystalline in nature having a hexagonal wurtzite type crystal structure with a preferred grain orientation in the (0 0 2) direction. Due to Cd doping, the degrees of polycrystallinity increased simultaneously and the orientation of the grains in the (0 0 2) axis is found to be deteriorated. Atomic force microscopy measurements reveal that the surface morphology of the films changes continuously with a decrease in the grain size due to Cd doping. Both photoluminescence and optical measurements showed that the band gap decreases from 3.12 to 2.96 eV with increasing Cd concentration. Increasing the Cd concentration also leads to the broadening of the emission peak and degrading the crystalline quality. The films are highly transparent in the visible region and the absorption edge showed a red shift. The sheet resistance of pure ZnO has been determined as 650 Ω sq−1 cm−1 and is decreased for higher concentrations of Cd doping. The characterization studies clearly indicate the incorporation of Cd into ZnO; hence the observed decrease in the optical band gap and electrical resistivity can be directly attributed to the effect of Cd ion incorporation into the ZnO lattice.

The structural and optical properties of pure and zinc doped tin oxide (SnO2) thin films have been studied in detail. Thin films of pure and zinc doped tin oxide (Zn : SnO2) were prepared on Si(1 0 0) and quartz substrates by the spray pyrolysis technique at a substrate temperature of 400 °C. The zinc dopant concentration was varied from 0 to 25 wt%. The films were systematically characterized by different methods to understand their structural and optical property variations, and the results were correlated. The x-ray diffraction (XRD) method shows that pure SnO2 films possess tetragonal crystalline structure with the preferred (1 1 0) orientation. Upon increasing the zinc concentration the preferred orientation changes from the (1 1 0) plane to the (2 0 0) plane, and at the same time the crystalline quality was found to be deteriorated. The Raman measurements also confirm the tetragonal structure of the films for the entire range of Zn doping. High resolution scanning electron microscopy measurements reveal that upon increasing the Zn concentration, the surface morphology of the films changes continuously and the grains also deteriorate. The elemental analysis of the films measured by energy dispersive XRD spectroscopy shows that the Zn concentration in the solid film is slightly less than that of the starting solution. Optical transmittance measurements of the films reveal that the films are fully transparent in the visible region. Upon increasing the Zn concentration, the band gap of the films decreases from 3.85 to 3.57 eV. Thus, the structural study performed by XRD and Raman spectroscopy clearly indicates the incorporation of Zn ion into SnO2 lattice, and the change in the optical properties of the films was directly attributed to the effect of Zn ion incorporation into SnO2 lattice.

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