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In this article, we investigate the effects of oxygen partial pressure in the deposition chamber on the optical properties of zinc oxide (ZnO) thin films; in particular, we examine the variation of the refractive index with oxygen flux. ZnO thin films were deposited by radio-frequency (RF) magnetron sputtering and studied by means of X-ray diffraction (XRD) and spectroscopic ellipsometry (SE). We have found a preferential c-axis growth of ZnO films, with slightly variable deposition rates from 2.6 to 3.8 angstrom/s. Conversely, the refractive index exhibits, from ultraviolet (UV) to near infrared (IR), a considerable and almost linear variation when the oxygen flux value in the deposition chamber varies from 0 to 10 seem.

Mn-55 nuclear magnetic resonance and magnetization studies of the series of La0.67Sr0.33MnO3 thin films have been performed at low temperature. Two distinct lines were observed, at 322 MHz and 380 MHz, corresponding to two different phases, the former located at the interface, with localized charges, and the latter corresponding to the film bulk, with itinerant carriers (as it was also found in Ca manganite films). The spin-echo amplitude was measured as a function of a dc magnetic field applied either in the film plane or perpendicular to it. The field dependence of the NMR signal intensity above the effective anisotropy field agrees well with a model of magnetically homogeneous sample. The enhanced magnetic anisotropy estimated for the NMR signal from the interface is consistent with its very small thickness, indicating similar magnetic properties in charge localized and itinerant regions.

55Mn nuclear magnetic resonance and magnetization studies of the series of La0.67Sr0.33MnO3 thin films have been performed at low temperature. Two distinct lines were observed, at 322 MHz and 380 MHz, corresponding to two different phases, the former located at the interface, with localized charges, and the latter corresponding to the film bulk, with itinerant carriers (as it was also found in Ca manganite films). The spin-echo amplitude was measured as a function of a dc magnetic field applied either in the film plane or perpendicular to it. The field dependence of both the main NMR signal intensity and frequency shift is quite consistent with that calculated in a simple single domain model. The best fit to the model shows that magnetization rotation processes play a dominant role when the applied field exceeds the effective anisotropy field. Distinctly different magnetic anisotropies are deduced from the interface NMR signal., Comment: 7 pages, 8 figures

A series of thiophenic monomers functionalized with different chromophoric groups have been optically characterized in view of preparation of polymeric films for second-order nonlinear optics and electrooptics. In order to investigate the optical behaviour inside a solid host matrix, the molecules have been physically dispersed in poly(methylmethacrylate) (PMMA) films and poled through high-temperature corona-poling for characterization through in situ second harmonic generation and ex situ angle-resolved spectroscopy. The values of dipole moment μ and optical hyperpolarizability β have been estimated inside the host matrix and related to the molecular structure. For one of the chromophores the long-term reorientation dynamics has been monitored in order to investigate the stability and the interaction with the polymeric environment. © 2001 Elsevier Science B.V.

Thin films of La0.67Ba0.33MnO3 were deposited on NdGaO3 by pulsed laser deposition with in situ RHEED diagnostics. A strong dependence of structural and electrical transport properties of the films on the background oxygen pressure was observed. Electrical resistance versus temperature and X-ray diffraction measurements were used to characterise the deposited films. Deposition at low background oxygen pressure (approximate to 10(-1) Pa) resulted in a good structural quality with an atomically flat surface, but poorer transport properties compared to films grown at higher pressure (approximate to 50 Pa). These observations have been correlated with the characteristics of the plume expansion by studying pulsed laser ablation of manganate samples into oxygen background gas by optical emission spectroscopy and ion probe diagnostics. These studies have been carried out using the parent LaMnO3 compound as target material in presence of an oxidizing atmosphere.