Florine Conchon

Effect of tensile and compressive strains on the transport properties of SmNiO3 layers epitaxially grown on (001) SrTiO3 and LaAlO3 substrates

This paper deals with the role of epitaxial strain on the structure and electronic transport properties of metastable SmNiO3 layers grown by metal-organic chemical vapor deposition onto SrTiO3 and LaAlO3 substrates. The characterization of these layers is carried out by high resolution x-ray diffraction and four-probe resistivity measurements. It is found that the SmNiO3 phase is stabilized by in-plane compressive strain whereas in-plane tensile strain induces the creation of oxygen vacancies that induces an annihilation of the metal-insulator transition and a huge increase of the resistivity.

X-ray diffuse scattering from stacking faults in thick 3C-SiC single crystals

Stacking faults in thick (001)- and (111)-oriented 3C-SiC single crystals are studied by high resolution x-ray diffraction. The authors demonstrate that the analysis of the diffuse scattering intensity distribution can be used as a nondestructive means to accurately determine the densities of Shockley-type stacking faults. The diffuse scattering intensity is simulated with a scattering model based on a difference-equation description of faulting in fcc materials. It is shown that the (001) SiC crystals exhibit an anisotropic fault distribution, whereas the (111) SiC crystals exhibit an isotropic fault distribution, in excellent quantitative agreement with transmission electron microscopy observations.

Reciprocal-space mapping of epitaxic thin films with crystallite size and shape polydispersity

A development is presented that allows the simulation of reciprocal-space maps (RSMs) of epitaxic thin films exhibiting fluctuations in the size and shape of the crystalline domains over which diffraction is coherent (crystallites). Three different crystallite shapes are studied, namely parallelepipeds, trigonal prisms and hexagonal prisms. For each shape, two cases are considered. Firstly, the overall size is allowed to vary but with a fixed thickness/width ratio. Secondly, the thickness and width are allowed to vary independently. The calculations are performed assuming three different size probability density functions: the normal distribution, the lognormal distribution and a general histogram distribution. In all cases considered, the computation of the RSM only requires a two-dimensional Fourier integral and the integrand has a simple analytical expression, i.e. there is no significant increase in computing times by taking size and shape fluctuations into account. The approach presented is compatible with most lattice disorder models (dislocations, inclusions, mosaicity, ...) and allows a straightforward account of the instrumental resolution. The applicability of the model is illustrated with the case of an yttria-stabilized zirconia film grown on sapphire.

Investigation of strain relaxation mechanisms and transport properties in epitaxial SmNiO3 films

This article deals with strain relaxation in SmNiO3 epitaxial films deposited by chemical vapor deposition on SrTiO3 substrates. Thanks to x-ray reciprocal space mapping, we demonstrate that the strain relaxation is driven both “chemically” and “mechanically” by the formation of oxygen vacancies and misfit dislocations, respectively. Besides, a careful interpretation of the resistivity measurements allows us to highlight a correlation between the formation of oxygen vacancies, the stabilization of Ni3+, and the metal-insulator transition in the SmNiO3 films. Furthermore, using coplanar and grazing incidence diffraction, the shape of the strain gradient within the films is retrieved. This latter is calculated using a versatile scattering model involving B-spline functions. Finally, particular planar faults Ruddlesden–Popper faults that give rise to extended diffuse scattering on transverse scans are analyzed using a recent phenomenological model

Epitaxial stabilization of SmNiO3 films on (0 0 1) SrTiO3 substrates

The epitaxial stabilization of SmNiO3 (SNO) films grown by an injection MO-CVD process on (0 0 1) SrTiO3 (STO) substrates is discussed. By means of high-resolution x-ray diffraction, we show for the first time that SNO can be stabilized on STO with a minor amount of secondary phases and with a layer thickness reaching several hundreds of nanometres. It is argued that this stabilization is achieved because the lattice mismatch between these two perovskites is not as high as expected (1.8% instead of 2.8%). Moreover, the well-known dissociation of the SNO phase into NiO and Sm2O3 has been clearly correlated with the relaxation of epitaxial strain which is driven by the formation of misfit dislocations.

High-resolution X-ray diffraction analysis of strain relaxation in epitaxial oxide thin films

High-resolution X-ray diffraction analysis of strain relaxation in epitaxial oxide thin films Rene Guinebretiere, Florine Conchon, Alexandre Boulle, Cecile Girardot, Stephane Pignard, Eric Dooryhee, Jean Louis Hodeau Lab. Science des Procedes Ceramique et de Traitements de Surface, ENSCI, 47, Av. A. Thomas, Limoges, Limousin, 87065, France, LMGP UMR CNRS 5628, INP Grenoble, MINATEC, 3 parvis Louis Néel BP 257, 38016 Grenoble, France, IN CNRS UPR 2940, 25 avenue des Martyrs BP 166, 38042 Grenoble France, E-mail:rene.guinebretiere@ unilim.fr