C. Le Paven-Thivet

YBa2Cu3O7 films epitaxially grown on MgO, LaAlO3, SrLaAlO4 and Al2O3 substrates structural and superconducting properties in correlation with the microwave surface resistance and the far-infrared transmittance

YBa2Cu3O7 epitaxial films have been grown by laser ablation on MgO, LaAlO3, SrLaAlO4 and Al2O3 substrates. Films on LaAlO3 have excellent structural, superconducting and microwave properties, reflected by surface-resistance (RS) values systematically in the range 0.5–1 mΩ (10 GHz, 77 K). On MgO substrates, such low RS (<0.50 mΩ) values can be reached on both fully “normal-0°” and “45°” in-plane oriented YBa2Cu3O7 films, whereas in mixed (0°–45°) films the presence of the high-angle grain boundaries leads to a surface resistance larger than 100 mΩ. On SrLaAlO4 and bare Al2O3 substrates, despite good superconducting properties, obtained for sapphire due to the specific substrate surface treatment, the structural quality and surface resistance are moderate. The latter results are in complete agreement with the correlation we have demonstrated between structural quality and surface resistance as well as far-infrared transmittance. We also point out the importance of a RS determination as an intrinsic superconducting parameter: the absence of a direct correlation with low-frequency measurements shows that the latter are not sufficient to fully characterize the superconducting thin films.

Structure and morphological study of nanometer W and W3O thin films

Abstract In this paper, the structure of nanometer tungsten thin films has been correlated to their surface morphology. Films have been deposited by RF-sputtering at a working pressure of 0.5 Pa and with a power density of 1.18 W/cm 2 . Two phases with different morphology have been observed: W 3 O with a nanograins structure is present in the first step of the tungsten growth; and, when the thickness is increased, a pure tungsten Wolfram phase (W) with a lamellar structure appears. We demonstrate that W 3 O is related to a pollution of the target surface between two growth runs. We succeed to suppress this phase and to obtain pure tungsten Wolfram nanolayer, in order to realize (W/WO 3 ) n multilayer.

Effects of in-plane high angle grain boundaries in YBa2Cu3O7 thin films epitaxially grown on (100) MgO on their physical properties

Abstract In laser ablation epitaxially grown YBa 2 Cu 3 O 7 (YBCO) films on (100) MgO, two in-plane orientations, called c 10 and c 145 compete, leading to an array of High Angle Grain Boundaries (HAGB). The ratio of these two in-plane orientations has been measured by XRD ϕ-scans. The HAGB density correlates strongly and similarly with both the surface resistance and the area under the χ″ AC susceptibility curve, giving also a strong evidence for a relation between these two data. In contrast no actual correlation has been found with any other structural or physical characteristic.

Growth and characterization of HTSC thin films for microelectronic devices

General techniques for the growth of heteroepitaxial HTSC thin films are shortly reviewed, and some recent trends are emphasized. The crystallographic characterization of such films is described in detail, including various X-ray diffraction settings, as well as electron diffraction and channelling methods. Among physical characterizations, the microwave measurements are highly defect sensitive, and a clear correlation between the microstructure, the a.c. susceptibility losses and the surface resistance is reported. Finally, main trends about potential applications are given.

LaTiO x N y Thin Films, Measurement and Application to Microwave Device

This paper reports about three issues: a non-destructive method for dielectric measurement of materials; the first microwave dielectric measurement of a new birth dielectric LaTiOxNy material, and a topology for X-band phase shifter based on tuneable ferroelectric thin films interdigital capacitors.