Cristian Mocuta - Academia.edu (original) (raw)

Papers by Cristian Mocuta

Journal of Applied Physics, Jun 1, 2020

Journal of Applied Physics, Oct 26, 2017

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

ACS applied electronic materials, May 18, 2022

$Research paper thumbnail of First examinations of ancient ferrous alloys in Renaissance armour by SR-X-Ray diffraction$

The European Physical Journal Plus

Materials Advances

Solvent annealing at around 300 °C resulted in a significant modification of the structure and th... more Solvent annealing at around 300 °C resulted in a significant modification of the structure and the magnetic properties of core–shell metal oxide nanoparticles as shown by DANES and XMCD.

$Research paper thumbnail of In situ X-ray diffraction studies on the piezoelectric response of PZT thin films$

Thin Solid Films, Mar 1, 2016

Acta Crystallographica Section A Foundations and Advances, 2021

Materials Advances, 2022

Epitaxial perovskite self-oxidized oxynitride N:BaTiO3 thin films, deposited on 1% Nb-doped SrTiO... more Epitaxial perovskite self-oxidized oxynitride N:BaTiO3 thin films, deposited on 1% Nb-doped SrTiO3(001) single crystals, were obtained by atomic nitrogen assisted molecular beam epitaxy without supplying additional oxygen gas. Their growth,...

OAJ Materials and Devices, 2021

Nanometric laminar two-dimensional artificial multiferroic oxide thin films can be elaborated usi... more Nanometric laminar two-dimensional artificial multiferroic oxide thin films can be elaborated using spinel ferrites and perovskite ferroelectrics like CoFe2O4 and BaTiO3. Such materials can retain their individual ferromagnetic or ferroelectric properties. In the thin epitaxial film regime a cross coupling of these properties is possible thanks to strain engineering. After introducing the concepts supporting artificial multiferroic laminar structures, the growth of strained BaTiO3 thin films and the growth of subsequent Co-ferrites layers will be detailed. With respect to the relative film thickness, a detailed understanding of the elastic behavior of these films will be proposed based on the characterization using several synchrotron radiation techniques including x-ray specular and off-specular diffraction, x-ray absorption spectroscopy, as well as x-ray magnetic circular dichroism.

Physical Review Materials, 2021

Journal of Physics D: Applied Physics, 2020

We report on the growth of thin NiSi films via the thermal reaction of Ni layers (13–35 nm) with ... more We report on the growth of thin NiSi films via the thermal reaction of Ni layers (13–35 nm) with Si(100) substrates modified by ion implantation. By introducing substrate damage or nitrogen impurities prior to the solid-phase reaction, several properties of the NiSi films can be modified: the formation temperature, texture, diffusion-limited growth rate and morphological stability. As some of the modifications to the NiSi films are rooted in the early silicide phases preceding the NiSi phase, particularly its formation temperature, special attention is devoted to the growth of the amorphous Ni-Si alloy and the crystalline δ-Ni2Si and θ-Ni2Si phases. We employed a number of experimental techniques, including in situ synchrotron x-ray diffraction (XRD), in situ Rutherford backscattering spectrometry (RBS), in situ sheet resistance measurements, ex situ ion beam channelling and ex situ pole figure measurements. We show that both the formation temperature of the NiSi films and the inten...

$Research paper thumbnail of Revealing the role of microstructure architecture on strength and ductility of Ni microwires by in-situ synchrotron X-ray diffraction$

Scientific Reports, 2019

Deformation mechanisms of cold drawn and electropolished nickel microwires are studied by perform... more Deformation mechanisms of cold drawn and electropolished nickel microwires are studied by performing in-situ monotonous and cyclic tensile tests under synchrotron radiation. X-ray diffraction tests allow probing elastic strains in the different grain families and establishing a link with the deformation mechanisms taking place within the microwires. The measurements were carried out on several microwires with diameters ranging from as-drawn 100 µm down to 40 µm thinned down by electropolishing. The as-drawn wires exhibit a core-shell microstructure with <111> fiber texture dominant in core and heterogeneous dual fiber texture <111> and <100> in the shell. Reduction of specimen size by electropolishing results in a higher yield stress and tensile strength along with reduced ductility. In-situ XRD analysis revealed that these differences are linked to the global variation in microstructure induced by shell removal with electropolishing, which in turn affects the load...

Journal of Applied Physics, 2012

We have investigated the growth of BaTiO3 thin films deposited on pure and 1% Nb-doped SrTiO3(001... more We have investigated the growth of BaTiO3 thin films deposited on pure and 1% Nb-doped SrTiO3(001) single crystals using atomic oxygen assisted molecular beam epitaxy and dedicated Ba and Ti Knudsen cells. Thicknesses up to 30 nm were investigated for various layer compositions. We demonstrate 2D growth and epitaxial single crystalline BaTiO3 layers up to 10 nm before additional 3D features appear; lattice parameter relaxation occurs during the first few nanometers and is completed at ∼10 nm. The presence of a Ba oxide rich top layer that probably favors 2D growth is evidenced for well crystallized layers. We show that the Ba oxide rich top layer can be removed by chemical etching. The present work stresses the importance of stoichiometry and surface composition of BaTiO3 layers, especially in view of their integration in devices.

$Research paper thumbnail of Nano-structuration effect on the mechanical behavior of gold thin films studied by 2D synchrotron x-ray diffraction$

Surface & Coatings Technology, Dec 1, 2016

Thin film technology is pervasive in microelectronics, and in optical, magnetic or micro-mechanic... more Thin film technology is pervasive in microelectronics, and in optical, magnetic or micro-mechanical devices. The mechanical performance of such nanoscale structure is crucial for applications since it is related to device lifetime. Furthermore, the mechanical behavior of nanostructured materials is still not well known. In this work, nanostructured gold thin films with different thicknesses have been elaborated by sequenced ion beam sputtering to study size effect. The grain size is controlled by stopping the grain growth during the thin film growth. Using the biaxial tensile setup developed at the DiffAbs beamline of the French synchrotron facility SOLEIL, x-ray diffraction (XRD) measurements have been performed during controlled biaxial deformation tests on gold thin films deposited on Kapton substrate. Strain analysis of the gold thin films with different grain size and architecture has been achieved for a non equi biaxial loading with a force ratio of 0.8. XRD allows measuring the intra-granular strains using the so-called sin²ψ method while the macroscopic in-plane strains are measured simultaneously thanks to Digital Image Correlation. By analyzing the mechanical response of the different films, we conclude that gold thin films follow a plastic deformation mode whatever the grain size or thin film architecture.

Materials Letters, Apr 1, 2020

The local atomic structure of an Mg-1.44Nd (wt.%) alloy was investigated after solution annealing... more The local atomic structure of an Mg-1.44Nd (wt.%) alloy was investigated after solution annealing, high-pressure torsion (HPT) processing up to1 and 10 turns and ageing at 250 °C for 5 h using X-ray absorption fine structure (XAFS) measurements at the Nd LIII-edge. The results show that HPT processing has no effect on the atomic structure around Nd atoms compared to the unprocessed state, whereas ageing at 250 °C for 5 h induces a significant modification in the coordination number and interatomic distances around the Nd atoms. These variations are analyzed based on the correlations between precipitation, defects and atomic mobility of the chemical species.

$Research paper thumbnail of Coherent X-ray diffraction imaging of non-periodic single objects$

Acta Crystallographica Section A, Aug 23, 2008

Surface Science, Jun 1, 2001

Fe 0:65 Ni 0:35 ultrathin ®lms 3.5 monolayer thick have been grown on a vicinal Cu(1 1 1) surface... more Fe 0:65 Ni 0:35 ultrathin ®lms 3.5 monolayer thick have been grown on a vicinal Cu(1 1 1) surface in order to correlate the in-plane step-induced magnetic anisotropy deduced from X-ray magnetic circular dichroism (XMCD) to the crystal structure and morphology of the ®lms obtained by scanning tunneling microscopy and surface extended X-ray absorption spectroscopy. Magnetic moments are derived by applying the well-known sum rules to XMCD data and their anisotropies are determined by measurements obtained through various geometric conditions implying dierent polar and azimuth angles. The results for 3.5 ML alloy ®lms show that the orbital moment M L depends strongly on the azimuth angles while the eective spin moment M eff S is found nearly isotropic. We explain the strong in-plane orbital moment anisotropy in the light of the structural in-plane strains induced by the steps, the growth mode and the lattice parameter relaxation in this thickness range.

$Research paper thumbnail of Combined X-ray absorption and X-ray diffraction under high pressure$

High Pressure Research, Jul 2, 2016

I-III-VIZ compounds CuGaS,, CuGaS%, CuFeS, and CuFeSe, have been studied by x-ray absorption spec... more I-III-VIZ compounds CuGaS,, CuGaS%, CuFeS, and CuFeSe, have been studied by x-ray absorption spectroscopy and x-ray diffraction as a function of pressure. The combination of both techniques allowed the complete determination of the structures in their whole stability range. The equation of state of these compounds have been determined, as well as the volume compression at the transitions. The recovered phases after a pressure cycle are identical to the initial phases.