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The study explains the superconducting properties of films that are deposited from micro-, nanocrystalline and optimally BaZr[O.sub.3] (BZO)-doped Y[Ba.sub.2][Cu.sub.3][O.sub.6X] (YBCO) targets. The doping is found to highly improve the properties of these films.

Investigating the transition in laser ablated films by increasing the barium concentration or by suppressing the potential Nd/Ba substitution by doping with calcium is discussed. It shows that the Ca-doped NBCO films have exceptionally smooth surfaces, but suggests their properties have a comparatively much weaker dependence on growth conditions.

We report the localized charge carrier transport of two-phase composite ZnNiO/NiO (0 ≤ x ≤ 1) using the temperature dependence of ac-resistivity ρ( T) across the Néel temperature T (= 523 K) of nickel oxide. Our results provide strong evidence to the variable range hopping of charge carriers between the localized states through a mechanism involving spin-dependent activation energies. The temperature variation of carrier hopping energy ε( T) and nearest-neighbor exchange-coupling parameter J( T) evaluated from the small poleron model exhibits a well-defined anomaly across T. For all the composite systems, the average exchange-coupling parameter ( J) nearly equals to 70 meV which is slightly greater than the 60-meV exciton binding energy of pure zinc oxide. The magnitudes of ε (∼0.17 eV) and J (∼11 meV) of pure NiO synthesized under oxygen-rich conditions are consistent with the previously reported theoretical estimation based on Green's function analysis. A systematic correlation between the oxygen stoichiometry and, ε( T) and J( T) is discussed. [ABSTRACT FROM AUTHOR]

The InGaN thin films with indium content of x = 14-18 at.% were successfully grown by using molecular beam epitaxy (MBE) at high growth temperatures from 650°C to 800°C. In situ reflection high-energy electron diffraction (RHEED) of the InGaN films confirmed the Stranski-Krastanov growth mode. X-ray diffraction (XRD) of the films confirmed their highly crystalline nature having c-axis orientation with a small fraction of secondary InN phase admixture. High-resolution cross-sectional scanning electron microscopy images showed two-dimensional epilayers growth with thickness of about ∼260 nm. The high growth temperature of InGaN epilayers is found to be favorable to facilitate more GaN phase than InN phase. All the fundamental electronic states of In, Ga, and N were identified by x-ray photoelectron spectroscopy (XPS) and the indium composition has been calculated from the obtained XPS spectra with CASAXPS software. The composition calculations from XRD, XPS and photoluminescence closely match each other. The biaxial strain has been calculated and found to be increasing with the In content. Growing InGaN at high temperatures resulted in the reduction in stress/strain which affects the radiative electron-hole pair recombination. The InGaN film with lesser strain showed a brighter and stronger green emission than films with the larger built-in strain. A weak S-shaped near band edge emission profile confirms the relatively homogeneous distribution of indium. [ABSTRACT FROM AUTHOR]

Highlights: [•] GaN:Yb3+ NRs grown on different substrates are obtained by rf Plasma assisted MBE. [•] Optical characterization and crystal field calculation of GaN:Yb3+ NRs are established. [•] CL spectra of GaN:Yb3+ NRs show the presence of two main Yb3+ optical centers. [•] The effect of the nano structure on the Yb3+ optical centers was investigated. [•] The dominant Yb3+ optical center in the GaN NRs is the complex VN–Yb center. [ABSTRACT FROM AUTHOR]