Strongly electronic-correlated material as VO 2 has been investigated for ultrafast electronic applications due to their rapid and reversible Metal-Insulator transition. In this paper we report the design, simulation and fabrication of V O2 -based RF-switches in two configurations (shunt and series). In order to achieve this goal thin layers of VO 2 have been integrated with coplanar waveguides for the fabrication of microwave switches with thermally activated ON/OFF states. The MOCVD VO 2 films were grown on sapphire substrates and have been characterized by XRD, AFM and Raman spectroscopy. The modeling and simulation results have been found to be in good agreement with the experimental RF measurements.

The electronic structure, elastic constants, and magnetic properties of lanthanum cobaltite oxide \(\hbox {La}_{4}\hbox {Co}_{3}\hbox {O}_{9}\) compound, which crystallizes in orthorhombic space group Pnma, are investigated theoretically for the first time using the full potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory plus Hubbard correction term (DFT \(+\) U). The calculated equilibrium lattice constants and fractional atomic coordinates are in a good agreement with available experimental data. Our result for the formation energy and elastic constants confirms that the predicted \(\hbox {La}_{4}\hbox {Co}_{3}\hbox {O}_{9}\) is mechanically stable. This compound is found to be ductile in nature in accordance with Pugh’s criteria. The anisotropy factors (\({A}_{1})\), (\({A}_{2})\), and (\({A}_{3})\) of \(\hbox {La}_{4}\hbox {Co}_{3}\hbox {O}_{9}\) material are also predicted through the elastic constants. The electronic band structures show metallic behavior; the conductivity is mostly governed by Co-3d and O-2p states. The total magnetic moments of the tetrahedral (\(\hbox {CoO}_{4})\) and octahedral (\(\hbox {CoO}_{6})\) environments are, respectively, 2.502 \(\mu _{B}\) and 2.874 \(\mu _{B}\), which are consistent with the experimental measurements.

Based on the density functional theory (DFT), we elucidate the origin of magnetization in non-magnetic cubic halide perovskite CsCdM 3 ( M = Cl and Br) induced by substitution of non-magnetic 2 p -impurities (B, C, and N) substitution. The calculations were done within the generalized gradient approximation (GGA) and GGA plus-modified Becke and Johnson (mBJ-GGA) as the exchange correlation. The results reveal that half-metallic ferromagnetism can be obtained for C- and N-dopings with the integer magnetic moment of 3.00 and 2.00 µ B per cell. However, B substitution does not induce magnetism in both CsCdCl 3 and CsCdBr 3 systems. The localized magnetic moments substantially come from impurity atoms. The origin of ferromagnetism can be attributed to the p - p hybridization between 2 p -impurities and its surrounding halide atoms. Our results show that doped perovskites could provide a new promising class of materials for future spintronics applications.

The phenomenon of resistive switching (RS), which was initially linked to non-volatile resistive memory applications, has recently also been associated with the concept of memristors, whose adjustable multilevel resistance characteristics open up unforeseen perspectives in cognitive computing. Herein, we demonstrate that the resistance states of Li(x)CoO2 thin film-based metal-insulator-metal (MIM) solid-state cells can be tuned by sequential programming voltage pulses, and that these resistance states are dramatically dependent on the pulses input rate, hence emulating biological synapse plasticity. In addition, we identify the underlying electrochemical processes of RS in our MIM cells, which also reveal a nanobattery-like behavior, leading to the generation of electrical signals that bring an unprecedented new dimension to the connection between memristors and neuromorphic systems. Therefore, these LixCoO2-based MIM devices allow for a combination of possibilities, offering new perspectives of usage in nanoelectronics and bio-inspired neuromorphic circuits.

The highly temperature-dependent resistivity of the La2/3Sr1/3MnO3 (LSMO) manganite is taken as an advantage in a pressure sensor design based on the Pirani effect. Thin epitaxial films are grown on silicon substrate thanks to a SrTiO3 buffer layer that allows the fabrication of freestanding bridges by means of clean-room processes. The devices are then heated by Joule effect and their temperature modulated by heat transfer through the surrounding gas. The higher the current flowing in the bridge, the larger the resistance variation with pressure is, due to the Pirani effect. The heating current and device geometry are tuned in order to stay in a monotonous regime, avoiding the change of sign of the LSMO temperature coefficient. A sensitivity increased by a factor of 3 and a power consumption reduced by 5 orders of magnitude are measured by comparing oxide devices with conventional metallic ones of same geometry.

Cubic and tetragonal surfaces of BaTiO3 are investigated using the density functional theory (DFT) within the new generalized gradient approximation of Wu and Cohen (GGA-WC) to the exchange and correlation functional. The cubic and tetragonal surfaces of BaTiO3 are compared. For the tetragonal phase, we take into account two surface orientations (001) and (100) noted Tz and Tx, respectively. The atomic rumpling and the difference between interlayer distances are determined and compared to the experimental results as well as to previous theoretical ones. Atomic displacements are also highlighted by comparing the variation of c/a ratio along the selected surface slabs. Considerable tetragonality reduction is found for (001) surface termination of the tetragonal structure. This represents an important atomic redistribution compared to the other surfaces. Therefore, an important release of surface stress is noted for Tz termination. Stress is released for all BaO terminations in comparison with TiO2 terminations. Anisotropy of stress is noted for Tx terminations. The perpendicular polarization to the surface is cancelled due to electrostatic conditions of supercell construction. A parallel polarization is retained for BaO termination and not for TiO2 termination of Tx surface. Our findings are in good agreement with recent experimental ones.

The conduction mechanisms through a lead zirconate titanate (PZT) thin film grown by pulsed laser deposition with a La0.67Sr0.33MnO3 (LSMO) buffer layer on epitaxial Pt (111) were assessed in the 230–330K temperature range. X-Ray diffraction and transmission electron microscopy evidenced a columnar growth of (001)- and (011)-oriented PZT grains. The leakage current through the Pt/PZT/LSMO/Pt structure was then systematically measured. From current vs. time curves, a threshold voltage was found below which stable and reproducible current values are obtained, thus avoiding resistance degradation. The conduction mechanism changes from interface controlled at low temperatures to bulk controlled around room temperature. The hopping-type conductivity evidenced above 270K is consistent with the extended defects and columnar microstructure of the PZT film.

We describe a vector network analyzer-based method to study the electromagnetic properties of nanoscale dielectrics at microwave frequencies (1 MHz–40 GHz). The complex permittivity spectrum of a given dielectric can be determined by placing it in a capacitor accessed on its both electrodes by coplanar waveguides. However, inherent propagation delays along the signal paths together with frequency-dependent effective surface of the capacitor at microwave frequencies can lead to significant distortion in the measured permittivity, which in turn can give rise to artificial frequency variations of the complex permittivity. We detail a fully analytical rigorous correction sequence with neither recourse to extrinsic loss mechanisms nor to arbitrary parasitic signal paths. We illustrate our method on 3 emblematic dielectrics: ferroelectric morphotropic lead zirconate titanate, its paraelectric pyrochlore counterpart, and strontium titanate. Permittivity spectra taken at various points along the hysteresis loop help shedding light onto the nature of the different dielectric energy loss mechanisms. Thanks to the analytical character of our method, we can discuss routes to extend it to higher frequencies and we can identify unambiguously the sources of potential artifacts.

To reduce costs and to remain competitive in the worldwide electronics industry, semiconductor manufacturers continually miniaturize devices. Today, the interconnect lines linking electronic components have diameters of the order of 100nm or smaller. At the nanometre scale, strong size effects modify the mechanical properties of materials. To examine such effects, freestanding microbeams with geometrical and microstructural properties similar to those of interconnect lines have been designed. The yield stress dependence of the microbeams on their microstructure, shape and dimensions was investigated. As predicted by the Hall-Petch law, an increase in the yield stress with a decrease in the grain size was observed. In addition, a decrease in the cross-section of the microbeams at a fixed grain size led to a decrease in the yield stress. Hence, the yield domain of interconnect lines was observed to be controlled by two competitive size effects. This result imposes some restrictions on the design of electronic devices.

Electron beam (e-beam) exposure of insulating material gives rise to charge accumulation which degrades pattern resolution and position during lithography and observation. In this paper we propose a process which reduces significantly the artifacts due to charging effects by using a charge dissipater based on a bi-layer deposited on top of the insulating substrate. The first layer is an inorganic thin film and soluble in water at room temperature, while the second layer is a metallic thin film. We reported the results of this process during e-beam lithography and observation of insulating samples.

Ti/TiN multilayer and monolithic TiN nanocoatings have been deposited on Zr-based metallic glass substrates by means of RF sputtering technique at room temperature. Nanoindentation and nanoscratch tests are used to characterise the mechanical and tribological properties of coated samples. In addition, a Vickers indentation tests and scanning electron microscopy observation have been carried out to explore the deformation mechanism. When coated with the TiN and Ti/TiN multilayers, Zr60Ni10Cu20Al10 bulk metallic glass shows a significant enhancement of both apparent hardness and elastic modulus with a decrease of the friction coefficient. The Vickers indentation shows a fragile behaviour of TiN coatings compared to the Ti/TiN multilayer one. Based on Bhowmick model description, experimental nanoindentation approach is taken to determine the variation of shear stress as function of the penetration depth. It is found that the shear stress developed in the TiN coatings is higher than that observed in the Ti/TiN multilayer. A correlation between finite-element analysis results and experimental data has been proposed. The monolithic or multilayer type of coatings is found to have an influence on the stress and plastic deformation distributions.

Power dissipation is one of the most important factors limiting the future miniaturisation of integrated circuits. The capability of controlling magnetic states with a low voltage through magnetoelectric coupling in magnetostrictive/piezoelectric systems may pave the way toward ultra low-power electronics. Although the former effect has been demon-strated in several multiferroic heterostructures, the incorporation of such complex geometries into practical magnetic memory and logic nanodevices has been lacking. Here, we demonstrate the room temperature control of a domain wall gate with an electric field in a nanowire consisting of a laterally polarized piezoelectric bar inducing a giant strain in a ferromagnetic spin-valve. We propose to use such novel domain wall gate as an elementary brick to generate a complete set of boolean logic functions or stabilize domain walls in high density memory applications.

Des essais de nanoindentation instrumenté pour des chargements monotones et cycliques sur deux verres métalliques massifs (VMM) à base Zirconium ont été réalisés à température ambiante et avec une vitesse de chargement qui varie de 250 à 2500 μN/s. Nous avons trouvé que les chargements cycliques induisent un adoucissement qui semble être dépendant du nombre de cycles et du taux de chargement. L’effet de la vitesse de chargement a été comparé avec des essais effectués sur des échantillons du verre métallique à base Zirconium revêtus par des films de TiN et de CrN. La déformation inélastique dans le verre métallique à base Zirconium a été étudiée en analysant par microscopie à force atomique les empreintes résultantes des essais de nanoindentation. Le mécanisme de volume libre est proposé pour l’interprétation quantitative de ces observations.

Tantalum nitride (TaNx) films are usually used as barriers to the diffusion of copper in the substrate for electronic devices. In the present work, the TaNx coating plays an extra role in the iron catalyzed chemical vapor deposition production of carbon nanotubes (CNT). The CNTs were grown at 850°C on TaNx films prepared by radio frequency magnetron sputtering. The correlation between the CNT morphology and growth rate, and the pristine TaNx film nature, is investigated by comparing the evolution of the nano-composition, roughness and nano-crystallinity of the TaNx films both after annealing and CVD at 850°C.

For purpose of enhancement of mechanical properties, Al/Al2O3 films, with thickness A in the nanometric scale, were deposited on silicon substrate by reactive rf sputtering, at substrate temperatures Ts ranging from −90°C to 600°C. The characterisation (FEG-SEM, AFM, SIMS, XRR) has shown that Al/Al2O3 films are granular and rough, in correlation with the behavior of single alumnium films. The minimal roughness values are obtained at low Ts (−90°C and 25°C). The Λ = 20 rim-films are real multilayers, as confirmed by SIMS and XRR. Nevertheless, the multilayering character, i.e. The existence of multilayers, decreases when Ts increases. At low Ts, the relevant parameter to explain the weakness of stratification of Al/Al2O3 films is the roughness of layers, while at high Ts, the chemical interdiffusion clearly dominates, resulting in a no periodic structure at Ts = 600°C.

The influence of the size of crystalline regions on mechanical properties of irradiated oxides has been studied using magnesium aluminate spinel MgAl2O4. The samples characterized by different dimensions of crystalline domains, from sintered ceramics with grains of few micrometers in size up to single crystals, were used in the experiments. The samples were irradiated at room temperature with 320keV Ar2+ ions up to fluences reaching 5×1016cm−2. Nanomechanical properties were measured by using a nanoindentation technique and the resistance to crack formation by measurement of the total crack lengths made by Vickers indenter. The results revealed: correlation of nanohardness with accumulated damage, radiation-induced hardness increase in grain-boundary region and significant improvement of material resistance to crack formation.

The influence of the size of crystalline regions on mechanical properties of irradiated oxides has been studied using a magnesium aluminate spine! MgAl2O4. The samples characterized by different dimensions of crystalline domains, varying from sintered ceramics with grains of few micrometers in size up to single crystals, were used in the experiments. The samples were irradiated at room temperature with 320 keV Ar2+ ions up to fluences reaching 5 x 10(16) cm(-2). Nanomechanical properties (nanohardness and Young's modulus) were measured by using a nanoindentation technique and the resistance to crack formation by measurement of the total crack lengths made by the Vickers indenter. The results revealed several effects: correlation of nanohardness evolution with the level of accumulated damage, radiation-induced hardness increase in grain-boundary region and significant improvement of material resistance to crack formation. This last effect is especially surprising as the typical depth of cracks formed by Vickers indenter in unirradiated material exceeds several tens of micrometers, i.e. is more than hundred times larger than the thickness of the modified layer.

The effects of grain size on the nanomechanical properties of Ar-irradiated magnesium-aluminate spinels was studied. Spinel single crystals and ceramics of different grain size varying from ∼1μm up to few tens of micrometers were used in the experiments. The measurements were performed in both grain centers and grain boundaries and point to rapidly disappearing differences between bulk and boundaries in irradiated ceramics. The stress-induced hardening has been observed as well. This last effect depends on the grain size of the irradiated material and may serve as an indicator of the stress evolution in the irradiated samples.