This E4 section focuses on the preparation of thick and thin films of LTS and HTS materials and describes the base technologies used to develop sophisticated electronic and electrical applications. Low-Tc Josephson junctions are already processed into highly integrated planar structures consisting of 10 stacked Nb layers, with minimum feature size of 250 nm. The circuits include up to about 800,000 single junctions and are intended for low-energy-consumption processors and memories in single flux quantum (SFQ) logics. Other highly promising application directions are currently single photon detectors, superconducting spintronics, and hybrid devices of superconductors and other functional materials. Moreover, the more engineering-related coated conductors are also still a hot topic of research and application.

While the discovery of ‘High Temperature Superconductors’ (HTS) generated a considerable interest in the scientific community, the development of these materials in practical devices or conductors was delayed by the requirement of achieving high quality thin films with low angle grain boundaries (Dimos et al. 1990, Hilgenkamp et al. 2002, Graser et al. 2010) to reach acceptable transport current performances.

The efficiency of the superconducting radio frequency cavities composed of Nb required the deposition of thickness-controlled multilayer coatings of superconductor-insulator-superconductor (S-I-S) on the internal surfaces of the cavities. Herein, we report the plasma-enhanced atomic layer deposition of carbon-free NbN (50 mu m thick), followed by a thermal treatment, to obtain the superconducting layer in the S-I-S structure. Using (tert-butylimido)-tris(diethylamino)-niobium as the niobium precursor and H-2 and NH3 plasma as reactive gasses, the deposition and annealing parameters were optimized by studying their effects on the film properties (crystallinity, density, and composition). We demonstrated that the superconducting critical temperature (Tc) can be improved after thermal annealing up to 13.8 K, a value compatible with the targeted application. In addition to the expected densified layers and increased grain size, we observed a partial transformation of the oxide present in the as-deposited layer into niobium oxynitride, which could indicate the origin of the improvement of the superconducting properties. With low carbon and oxygen impurity concentrations in the films, this study contributes to the understanding of the relationship between the structure, composition, and superconductivity in NbN.

Superconducting radiofrequency (SRF) cavities for accelerators is the only superconductivity application that operates in the Meissner state. For decades, bulk niobium, which exhibits the highest 1st critical field among all known superconductors, has been the only material to achieve high accelerating fields in combination with a high quality factor. Specific nanostructures tailored for SRF applications, in the form of superconducting/insulating/superconducting multilayers, were proposed to surpass Nb performances that could improve SRF performance. In this paper, we present the study of a series of NbN/MgO/Nb tri-layers including standard material characterization and specific superconducting characterization (local magnetometry) along with a comparison to the current state-of-the-art theoretical modeling. This study shows that such structures are effective to enhance the penetration field compared to bare niobium, even in the presence of numerous defects.

Synthesis of thin niobium nitride (NbN) layers by High Temperature Chemical Vapor Deposition (HTCVD) is presented and the crystallographic orientations are investigated during heteroepitaxial growth on (0001)Al2O3, (0001)AlN template and 112¯0Al2O3. The HTCVD NbN layers are ex-situ characterized by means of X-ray diffraction (XRD) methods, Raman spectroscopy and Transmission Electron Microscopy (TEM). Depending on the deposition temperature, hexagonal NbN or fcc (face-centered cubic) δ-NbN is obtained. Orientation relationships between the fcc δ-NbN layer with respect to the substrates are given. We discuss the role of an AlN layer as a possible protective layer of the sapphire for the synthesis of fcc δ-NbN.

Functional properties of tin doped indium oxide (ITO) layers grown by MOCVD from different indium and tin precursors are investigated. Selected indium precursors are In(acac)(3), In(tmhd)(3) and InMe(2)OtBu, and tin precursors are DBTDA and Sn(acac)(2). ITO layers are optically and electrically characterized to determine the better doping conditions. Differences in electrical properties of ITO layers are found when using (InMe2OBu)-Bu-t, as compared to In(acac)(3) and to In(tmhd)(3). The best films present a resistivity of 2.5 x 10 (4) Omega cm and a transmittance higher than 84% for high deposition temperatures (T >= 600 degrees C). The nature of tin precursors modifies the optimal doping at which these characteristics are achieved. When doped by DBTDA optimal doping is 8 at.%, therefore close to the solubility limit of tin in In2O3 matrix; but when using Sn(acac)(2), or In(acac)(3)/DBTDA combination, best functional characteristics are obtained for the maximal doping content obtained, i.e. 2.5 at.%. For optimized conditions, the resistivity decreases when deposition temperature increases except when using the couple InMe(2)OtBu/DBTDA without oxygen addition during deposition. For this combination of precursors a resistivity of 1 x 10 (3) Omega cm is obtained at a deposition temperature of 350 degrees C and remains constant up to 600 degrees C. Only the films obtained from InMe(2)OtBu/DBTDA are crystalline state at a deposition temperature of 350 degrees C. (C) 2014 Elsevier B.V. All rights reserved.

Consider a layer of a gel attached to a rigid substrate, immersed in a solvent, and swelling in the thickness direction. The flat surface of the gel remains stable if the swelling ratio is small, but becomes unstable if the swelling ratio is large. While creases have been commonly observed, wrinkles have also been observed under certain conditions. We compare the critical conditions for the onset of creases and wrinkles by using a nonlinear field theory of gels. The critical swelling ratio for the onset of creases is calculated by using a finite element method, and that for wrinkles is calculated by using an analytical method. We find that the critical swelling ratio for the onset of creases is significantly lower than that for wrinkles.

We investigate three indium and two tin precursors for metalorganic chemical vapor deposition to highlight their influence on the resulting indium oxide or tin doped indium oxide (ITO) layers. Selected indium precursors are In(acac)(3), In(tmhd)(3) and (InMe2OBu)-Bu-t, and tin precursors are DBTDA and Sn(acac)(2). Acetyl acetonate ligand is identified to induce an organic contamination in the In2O3 and ITO layers when depositions are performed with In(acac)(3) or Sn(acac)(2) as precursor.The growth kinetic is also investigated. (InMe2OBu)-Bu-t presents a higher deposition rate and reactivity; besides the grown films crystallize at lower temperature as compared with the two other indium precursors. Moreover, it is the only studied indium precursors which allow synthesizing In2O3 and ITO layers without oxygen addition. Depending on the atmosphere, layers synthesized with (InMe2OBu)-Bu-t present different morphology. In particular, without oxygen addition, a (222) preferential orientation is detected by X-ray diffraction and correlated to a morphology composed of bundles of nanowires as evidenced by transmission electronic microscopy.Concerning tin doping in the ITO layer, incorporation is more efficient when using DBTDA than Sn(acac)(2) and when combined with (InMe2OBu)-Bu-t than with In(tmhd)(3) and In(acac)(3). (C) 2013 Elsevier B.V. All rights reserved.

A comparative analysis of Raman spectra from poly-domain PbTiO3 thin films with poly-domain and single-domain PbTiO3 crystals is presented. Raman spectroscopy reveals that the profiles of A1-symmetry modes can be significantly modified by the existence of the domain structure. The possible origins of these complex profiles of the A1(LO) and A1(TO) modes are discussed. It is emphasized that analysis of stresses, domain structure and phase transitions in the PbTiO3 thin films has to be based on the E(TO) modes presenting profiles that are not affected by the domain structure.

Rare earth nickelates RENiO3 which attract interest due to their sharp metal-insulator phase transition, are instable in bulk form due to the necessity of an important oxygen pressure to stabilize Ni in its 3+ state of oxidation. Here, we report the stabilization of rare earth nickelates in [(SmNiO3)t/(NdNiO3)t]n thin film multilayers, t being the thickness of layers alternated n times. Both bilayers and multilayers have been deposited by Metal-Organic Chemical Vapour Deposition. The multilayer structure and the presence of the metastable phases SmNiO3 and NdNiO3 are evidenced from by X-ray and Raman scattering. Electric measurements of a bilayer structure further support the structural quality of the embedded rare earth nickelate layers.

La2Zr2O7 (LZO) thin films are used as buffer layers in second generation high Tc superconductor tapes. The microstructure of LZO films grown by metalorganic decomposition is characterized by the presence of nanovoids throughout the whole thickness of the films. We introduced an out-gassing plateau under vacuum during the pyrolysis process to decrease the size of voids. The temperature of this plateau was determined by Fourier transformed infrared spectroscopy, electron back scattering diffraction and X-Ray diffraction characterizations. The dwelling time was also varied. Transmission Electron Microscopy (TEM) studies revealed that a high heating ramp in combination with a less than an hour pyrolysis plateau decreased pore size. The deposition rate during dip-coating was also decreased to enhance out-gassing at the plateau. Successive LZO layers were deposited and energy filtered TEM images at C K-edge were performed to identify the role of carbon in the nucleation mechanisms.

Synchrotron radiation at the European Synchrotron Radiation Facility has been used to characterize oxide thin films and multilayers grown by metal organic chemical vapor deposition (MOCVD). Reflectometry measurements were performed in the low angle region to get information on the quality of film/substrate and film/film interfaces of the heterostructures. The experimental data were compared to simulated spectra. High angle diffraction experiments were performed on superlattices of (BaTiO 3 /SrTiO 3 ) 15 and (La 2/3 Sr 1/3 Mn0 3 /SrTiO 3 ) 15 . The multilayers are oriented with the [001] direction perpendicular to the substrate plane. The 001 diffraction peaks were recorded up to the 008 one. The satellite peaks observed for both types of multilayers indicate the good coherence over the whole stacking. For the (BaTiO 3 /SrTiO 3 ) 15 systems, the diffraction peaks were particularly well resolved even for the highest order (008 peak), showing excellent epitaxial quality with abrupt interfaces for periods up to 16 nm.

The CeO2/La2Zr2O7/Ni piled-up structure is a very promising architecture for YBa2Cu3O7 (YBCO) coated conductors. We have grown YBCO/CeO2/LZO/Ni epitaxial structures by metalorganic decomposition (MOD) and metalorganic chemical vapor deposition (MOCVD) methods. The crystallographic quality of the CeO2 layer is not well determined by conventional X-ray diffraction (XRD) due to the superposition of LZO and CeO2 reflections. An alternative simple Raman spectroscopy analysis of the crystalline quality of the CeO2 films is proposed. The F2g Raman mode of CeO2 can be quantified either by using two polarization configurations (crossed or parallel) or at two different rotation angles around the normal axis (0° and 45°) to obtain information about the sample texture. The sample texture can be determined via a quality factor (referred to as the Raman intensity ratio, RIR) consisting of calculating the ratio of the integrated intensity of the CeO2 F2g mode at 0° and 45° in parallel polarization. This factor correlates with superconducting performance and the technique can be used as an on-line nondestructive characterization method.

La2Zr2O7 (LZO) films have been grown by metalorganic decomposition (MOD) to be used as buffer layers for coated conductors. A characteristic feature of LZO thin films deposited by MOD is the formation of nanovoids in an almost single crystal structure of LZO pyrochlore phase. Annealing parameters (heating ramp, temperature, pressure, etc.) were varied to establish their influence on the microstructure of the LZO layers. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used for sample characterization. The epitaxial pyrochlore phase was obtained for annealing temperatures higher than 850 degrees C whatever the other annealing conditions. However, the film microstructure, in particular, nanovoids shape and size, is strongly dependent on heating ramp and pressure during annealing. When using low heating ramp, percolation of voids creates diffusion channels for oxygen which are detrimental for the substrate protection during coated conductor fabrication. From this point of view high heating rates are more adapted to the growth of LZO layers. (C) 2009 Elsevier B.V. All rights reserved.

La2Zr2O7 (LZO) films have been grown by metalorganic decomposition (MOD) to be used as buffer layers for coated conductors. LZO can crystallize into two similar structures: fluorite or pyrochlore. Coated conductor application focuses on pyrochlore structure because it is a good barrier against oxygen diffusion. Classical x-ray diffraction is not able to separate the contribution of these two structures. Transmission electron microscopy and high-resolution transmission electron microscopy were used to determine the local distribution of these two phases in epitaxial LZO layers grown on LaAlO3. A characteristic feature of LZO thin films deposited by MOD is the formation of nanovoids in an almost single-crystal structure of LZO pyrochlore phase. For comparison, LZO layers deposited by metalorganic chemical vapor deposition were also studied. In this last case, the film is compact without voids and the structure corresponds to pyrochlore phase. Thus, the formation of nanovoids is a characteristic feature of MOD grown films.

The Ni-RABiTS/La2Zr2O7MOD/YBa2Cu3O7MOCVD structure is a promising architecture for (YBCO) coated conductors. We succeeded in growing highly textured superconducting YBCO films on LZO-buffered Ni-5at % W (NiW) substrates by metalorganic chemical vapor deposition (MOCVD). A single LZO buffer layer grown by metalorganic decomposition (MOD) is sufficient to ensure structural compatibility between YBCO and Ni, and to protect the substrate from oxidation during YBCO deposition. Textured Ni substrates obtained by rolling technique have intrinsic defects such as grain boundaries and rolling scratches. It is not easy to highlight their effects on LZO and YBCO films by usual measurements like XRD or SEM. The combination of Electron Backscattered Diffraction (EBSD) and Magneto-Optics imaging (MO) is useful to image grain boundaries and flux distribution in coated conductors. It provides complementary information on superconducting film qualities. These two techniques allowed us to understand how the microstructure of the LZO buffer layer and thus of the YBCO film is linked to the current density in this simple heterostructure.

A comparative analysis of Raman spectra from polydomain PbTiO3 thin films with both polydomain and single-domain PbTiO3 crystals is presented. The Raman signature of ferroelectric thin films is complex when used for stress analysis. Raman spectroscopy of a stress-free polydomain PbTiO3 single crystal reveals that the profile of phonon modes can be significantly modified by the existence of quasimodes. The different potential origins of quasimodes are discussed, and it is emphasized that quasimodes should be taken into account for an accurate estimation of residual stress values in ferroelectric films via Raman scattering. We finally propose and illustrate that the E(3TO) hard mode is more reliable for the estimation of biaxial residual stress in PbTiO3 than the commonly used E(1TO) soft mode.