A One-Pot Synthesis of "K(hfa) glyme" Adducts: Effect of the Polyether Length on the Ion Coordination Sphere

AbstractPotassium complexes are starting to gather more and more interest from academia and industry because of their intriguing application possibilities. Novel adducts of potassium hexafluoroacetylacetonato [K(hfa)] with polyethers (monoglyme, diglyme, triglyme, and tetraglyme) were synthesized through a single step reaction and characterized through FT‐IR spectroscopy as well as 1H and 13C NMR spectroscopy. Single crystal X‐ray diffraction studies enabled the identification of fascinating K coordination polymeric networks

Simulations of the Ultra-Fast Kinetics in Ni-Si-C Ternary Systems under Laser Irradiation

We present a method for the simulation of the kinetic evolution in the sub µs timescale for composite materials containing regions occupied by alloys, compounds, and mixtures belonging to the Ni-Si-C ternary system. Pulsed laser irradiation (pulses of the order of 100 ns) promotes this evolution. The simulation approach is formulated in the framework of the phase-field theory and it consists of a system of coupled non-linear partial differential equations (PDEs), which considers as variables the following fields: the laser electro-magnetic field, the temperature, the phase-field and the material (Ni, Si, C, C clusters and Ni-silicides) densities. The model integrates a large set of materials and reaction parameters which could also self-consistently depend on the model variables. A parameter calibration is also proposed, specifically suited for the wavelength of a widely used class of excimer lasers (λ = 308 nm). The model is implemented on a proprietary laser annealing technology computer-aided design (TCAD) tool based on the finite element method (FEM). This integration allows, in principle, numerical solutions in systems of any dimension. Here we discuss the complex simulation trend in the one-dimensional case, considering as a starting state, thin films on 4H-SiC substrates, i.e., a configuration reproducing a technologically relevant case study. Simulations as a function of the laser energy density show an articulated scenario, also induced by the variables’ dependency of the materials’ parameters, for the non-melting, partial-melting and full-melting process conditions. The simulation results are validated by post-process experimental analyses of the microstructure and composition of the irradiated samples

Properties of Al2O3 thin films deposited on 4H-SiC by reactive ion sputtering

In this work, the electrical properties of Al2O3 films deposited by reactive ion sputtering were investigated by means of morphological, chemical and electrical characterizations. We observe that the electron trapping affecting the insulating layer is mitigated after a rapid thermal annealing (RTA) treatment. The RTA improved also the permittivity (up to 6ε0), although the negative fixed charge remains in the order of 1012 cm−2. However, the temperature dependent electrical investigation of the metal-oxide-semiconductor (MOS) capacitors demonstrates that the room temperature Fowler-Nordheim electron barrier height of 2.37 eV lies between the values expected for SiO2/4H-SiC and Al2O3/4H-SiC systems

Mechanism of Grain Densification in Nano- and Poly-Crystalline Cu Films and Its Impact in Advanced Metallization Processes

We investigate the microstructural evolution of electrochemically deposited poly-crystalline Cu films during subsequent thermal process cycles at mild maximum temperatures, compatible with the integration in advanced metallization schemes for electronic device manufacturing. The modifications induced by the thermal budget have been characterized at different scales (from the film-substrate interface to the wafer scale) with different complementary techniques: X-ray Diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and dynamical warpage measurements. Moreover, the film internal grains’ evolution has been modelled by a tri-dimensional on-cell model, derived by the Pott-like multi-states configurational energy dependence, able to consider multiple orientation of the grains and densification kinetics in the canonical ensemble. Finally, a macroscopic model of the warpage dependence on the process conditions is discussed. The presented joint theoretical and experimental analysis provides a complete and consistent scenario of the grain densification phenomenon and its impact for the Cu film microstructure and the composite system morphology, indicating several strategies for the integration of the process in real device structures

Controlled Al3+ Incorporation in the ZnO Lattice at 188 °C by Soft Reactive Co-Sputtering for Transparent Conductive Oxides

Transparent conductive oxide (TCO) layers, to be implemented in photo-anodes for dye-sensitized solar cells (DSCs), were prepared by co-deposition of ZnO and Al using pulsed-direct current (DC)-magnetron reactive sputtering processes. The films were deposited at low deposition temperatures (RT-188 °C) and at fixed working pressure (1.4 Pa) using soft power loading conditions to avoid intrinsic extra-heating. To compensate the layer stoichiometry, O2 was selectively injected close to the sample in a small percentage (Ar:O2 = 69 sccm:2 sccm). We expressly applied the deposition temperature as a controlling parameter to tune the incorporation of the Al3+ species in the targeted position inside the ZnO lattice. With this method, Aluminum-doped Zinc Oxide films (ZnO:Al) were grown following the typical wurtzite structure, as demonstrated by X-ray Diffraction analyses. A combination of micro-Raman, X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry (SE) analyses has shown that the incorporated host-atoms are Al3+ species in Zn2+ substitutional position; their amount increases following a direct monotonic trend with the deposition temperature. Correspondently, the c-axis strain into the layer decreases due to the progressive ordering of the lattice structure and reducing clustering phenomena. The maximum average Al content inside the film was ~2%, as measured by energy dispersive X-ray (EDX) spectroscopy, with a uniform distribution of the dopant species along the layer thickness traced by depth-profile XPS analyses. The optimised ZnO:Al layer, deposited at a rate of ~7 nm/min, exhibits high transmittance in the visible range (~85%) and low resistivity values (~13 mΩ × cm). The material therefore fulfils all the requirements to be candidate as TCO for low-cost DSCs on flexible substrates for large area technologies

Bimodal Porosity and Stability of a TiO2 Gig-Lox Sponge Infiltrated with Methyl-Ammonium Lead Iodide Perovskite

International audienceWe created a blend between a TiO2 sponge with bimodal porosity and a Methyl-Ammonium Lead Iodide (MAPbI(3)) perovskite. The interpenetration of the two materials is effective thanks to the peculiar sponge structure. During the early stages of the growth of the TiO2 sponge, the formation of 5-10 nm-large TiO2 auto-seeds is observed which set the micro-porosity (47% V) and after MAPbI(3) loading, and after blend ageing, unfolding a starting pore filling above 80% in volume. The degradation of the perovskite in the blend follows a standard path towards PbI2 accompanied by the concomitant release of volatile species, with an activation energy of 0.87 eV under humid air. The use of dry nitrogen as environmental condition has a positive impact in increasing this energy by -0.1 eV that extends the half-life of the material to 7 months under continuous operation at 60 degrees C