[en] Highlights: • Highly dense LBF thin films with a compactness of ~99% have been prepared by physical vapor deposition. • An intrinsic conductivity of 9.10⁻⁵ S cm⁻¹ at 40 °C has been measured for LBF thin films deposited at T_substrate = 450 °C. • The thickness of the ultrathin oxyfluoride interface layer decreases with increasing of T_substrate (e ≈ 1 nm at 450 °C). -- Abstract: Dense thin films with tysonite-type structure La_1−xBa_xF_3−x (LBF, x = 0.08–0.09) and a thickness of ≈ 1.5 µm were deposited through physical vapor deposition (PVD) technique. For a better understanding of the film/substrate interface, layers with e ≈ 100 nm have also been studied. Grazing incidence X-ray diffraction analysis of these very thin films revealed the presence of Ba_xLa_1−xO_1−uF_1−x+2u (0 ≤ u ≤ x) oxyfluoride phase formed at the film/substrate interface. The thickness of the resistive oxyfluoride layer decreases with increasing of the substrate temperature T_s. The effect of T_s on the compactness, morphology and conductivity of the fabricated PVD films was established. The ionic conductivity was evaluated by electrochemical impedance spectroscopy in both configurations: in- and cross-plane. An intrinsic conductivity of 9.10⁻⁵ S cm⁻¹ at 40 °C with an activation energy of ≈ 0.45 eV related to the fluoride ion mobility was estimated from in-plane measurements for a thin film elaborated at T_s = 450 °C. This anionic conductivity value is close to that reported previously on a single crystal (2.10⁻⁴ S cm^–1 at 40 °C for x = 0.08). The improvement of the conductivity of LBF films with the growing substrate temperature is directly related to the increase in compactness which reaches 99% for T_s = 450 °C.

[en] We report on the charge spill-out and work function of epitaxial few-layer graphene on 6 H-SiC(0 0 0 1). Experiments from high-resolution, energy-filtered x-ray photoelectron emission microscopy (XPEEM) are combined with ab initio density functional theory calculations using a relaxed interface model. The work function values obtained from theory and experiments are in qualitative agreement, reproducing the previously observed trend of increasing work function with each additional graphene plane. Electron transfer at the SiC/graphene interface through a buffer layer (BL) causes an interface dipole moment which is at the origin of the graphene work function modulation. The total charge transfer is independent of the number of graphene layers, and is consistent with the constant binding energy of the SiC component of the C 1s core-level, measured by XPEEM. Charge leakage into a vacuum depends on the number of graphene layers, explaining why the experimental, layer-dependent C 1s graphene core-level binding energy shift does not rigidly follow that of the work function. Thus, a combination of charge transfer at the SiC/graphene interface and charge spill-out into the vacuum resolves the apparent discrepancy between the experimental work function and C 1s binding energy. (paper)

[en] We study the transport properties in SrVO_3/LaVO_3 (SVO/LVO) superlattices deposited on SrTiO_3 (STO) substrates. We show that the electronic conduction occurs in the metallic LVO layers with a galvanomagnetism typical of a 2D Fermi surface. In addition, a Kondo-like component appears in both the thermal variation of resistivity and the magnetoresistance. Surprisingly, in this system where the STO interface does not contribute to the measured conduction, the Kondo correction is strongly anisotropic. We show that the growth temperature allows a direct control of this contribution. Finally, the key role of vanadium mixed valency stabilized by oxygen vacancies is enlightened. (paper)

[en] We report on the electrical, optical and photoluminescence properties of industry-ready Al doped ZnO thin films grown by physical vapor deposition, and their evolution after annealing under vacuum. Doping ZnO with Al atoms increases the carrier density but also favors the formation of Zn vacancies, thereby inducing a saturation of the conductivity mechanism at high aluminum content. The electrical and optical properties of these thin layered materials are both improved by annealing process which creates oxygen vacancies that releases charge carriers thus improving the conductivity. This study underlines the effect of the formation of extrinsic and intrinsic defects in Al doped ZnO compound during the fabrication process. The quality and the optoelectronic response of the produced films are increased (up to 1.52 $\mathrm{m}\mathrm{\Omega <!--\; ??\; -->}\cdot <!--\; ???\; -->\mathrm{c}\mathrm{m}$ and 3.73 eV) and consistent with the industrial device requirements. (paper)

[en] The interplay between charge, spin, orbital and lattice degrees of freedom in transition metal oxides has motivated extensive research aiming to understand the coupling phenomena in these multifunctional materials. Among them, rare earth vanadates are Mott insulators characterized by spin and orbital orderings strongly influenced by lattice distortions. Using epitaxial strain as a means to tailor the unit cell deformation, we report here on the first thin films of PrVO₃ grown on (001)-oriented SrTiO₃ substrate by pulsed laser deposition. An extensive structural characterization of the PrVO₃ films, combining x-ray diffraction and high-resolution transmission electron microscopy studies, reveals the presence of oriented domains and a unit cell deformation tailored by the growth conditions. We have also investigated the physical properties of the PrVO₃ films. We show that, while PrVO₃ exhibits an insulating character, magnetic measurements indicate low-temperature hard-ferromagnetic behavior below 80 K. We discuss these properties in view of the thin-film structure. (fast track communication)

[en] While structure refinement is routinely achieved for simple bulk materials, the accurate structural determination still poses challenges for thin films due on the one hand to the small amount of material deposited on the thicker substrate and, on the other hand, to the intricate epitaxial relationships that substantially complicate standard x-ray diffraction analysis. Using both electron and x-ray diffraction, we analyze the crystal structure of epitaxial LaVO_3 thin films grown on (1 0 0)-oriented SrTiO_3. Transmission electron microscopy study reveals that the thin films are epitaxially grown on SrTiO_3 and points to the presence of 90° oriented domains. The mapping of the reciprocal space obtained by high resolution x-ray diffraction permits refinement of the lattice parameters. We finally deduce that strain accommodation imposes a monoclinic structure onto the LaVO_3 film. The reciprocal space maps are numerically processed and the extracted data computed to refine the atomic positions, which are compared to those obtained using precession electron diffraction tomography. (paper)

[en] The optical and electrical properties of transparent conducting oxide (TCO) thin films are strongly linked with the structural and chemical properties such as elemental depth profile. In R&D environments, the development of non-destructive characterization techniques to probe the composition over the depth of deposited films is thus necessary. The combination of Grazing-Incidence X-ray Fluorescence (GIXRF) and X-ray reflectometry (XRR) is emerging as a fab-compatible solution for the measurement of thickness, density and elemental profile in complex stacks. Based on the same formalism, both techniques can be implemented on the same experimental set-up and the analysis can be combined in a single software in order to refine the sample model. While XRR is sensitive to the electronic density profile, GIXRF is sensitive to the atomic density (i. e. the elemental depth profile). The combination of both techniques allows to get simultaneous information about structural properties (thickness and roughness) as well as the chemical properties. In this study, we performed a XRR-GIXRF combined analysis on indium-free TCO thin films (Ga doped ZnO compound) in order to correlate the optical properties of the films with the elemental distribution of Ga dopant over the thickness. The variation of optical properties due to annealing process were probed by spectroscopic ellipsometry measurements. We studied the evolution of atomic profiles before and after annealing process. We show that the blue shift of the band gap in the optical absorption edge is linked to a homogenization of the atomic profiles of Ga and Zn over the layer after the annealing. This work demonstrates that the combination of the techniques gives insight into the material composition and makes the XRR-GIXRF combined analysis a promising technique for elemental depth profiling. - Highlights: • Effect of annealing process on properties of Ga doped ZnO thin films is studied. • Evolution of optical properties are probed by spectroscopic ellipsometry. • Elemental depth profiling is obtained by GIXRF-XRR combined analysis. • Atomic reorganization of Ga profile is observed after annealing. • GiXRF/XRR is a promising fab-compatible non-destructive characterization technique.