The properties of titanium oxide thin films deposited by direct current magnetron sputtering of a Ti target are strongly dependent on the sputtering conditions. The aim of the present work is to investigate the discharge parameters such as plasma potential, discharge voltage, deposition rate, and ion composition of the discharge as a function of the oxygen partial pressure. The plasma potential, relative to the ground, is determined from the ion energy distribution. Working in the constant current discharge mode, we observe, with increasing oxygen partial pressure, a drop of the plasma potential, an increase of the discharge voltage, a drop of the deposition rate, and an inversion of the Ti+–TiO+ intensities. For a given discharge current and pressure, the drop of the plasma potential and the increase of the discharge voltage occur at the same gas composition while the drop of the deposition rate and the ion intensity inversion happen at an oxygen richer gas composition. Both transitions are linearly correlated and depend on the discharge current. For larger oxygen partial pressure, a third transition appears corresponding to an inversion between TiO+ and TiO2+ intensities. These results lead us to consider three regimes in the reactive sputtering of a Ti target.
To reduce maintenance and to increase the corrosion protection and lifetime of maritimestructures while complying with environmental standards, multilayer coatings are applied to protectsteel sections. A new generation of hybrid sol-gel and/or HiPIMS Ni-based thin films appear toconstitute an efficient pre-treatment before the anti-corrosion paint application. However, increasingthe number of coatings and associated interfaces may lead to coating failure due to stresses inducedby the different deposition processes. Therefore developing smart models to assess the stressdistribution along these multilayers appears of significant importance. The well-known Stoneyformula cannot be used for multilayers and owing to the large dimensions of the object to be protected.To assess an easily measurable curvature after deposition, thin steel sheets are used but do not respectany more the Stoney hypotheses. So we set up an analytical thermo-elasto-plastic model to evaluatethe stresses induced by depositions in each layer. This model is based on the various thermalexpansion coefficients of every coat. After extrapolation along the complete thickness, combiningsol-gel and PVD deposition smoothens the stress difference between steel and paint. The shearstresses at interface seems thus to be reduced. The evolution of the stress difference between layerswith the imposed deflection can predict the mechanical strength and the interface failure. In order toevaluate the quality of the model, in-situ four-point bending in SEM was performed to study of theadhesion between the various layers. The results deduced from the model are in good agreement withSEM images.
This article reports the design, construction, and first use of an experimental device consisting of a specially designed vacuum chamber equipped with a reactive sputtering magnetron (RSM) to be used for controlled deposition of thin films on a Si(100) flat substrate. The setup was designed to allow for in situ and real-time recordings of X-ray diffraction patterns during the growth of the deposited films and was installed in the X-ray diffraction and spectroscopy beamline emerging from a superconducting wiggler source at the Brazilian Synchrotron Light Laboratory. The first use of the RSM setup was an in situ and real-time X-ray diffraction study of processes of growth of multilayered aluminum nitride thin films, whereas the operation parameters of the reactor were sequentially changed. This sequential process led to the development of multilayered films. Alternate variations in chamber pressure and magnetron power density allowed us to obtain thin films composed of several micrometer thick layers, with alternate amorphous and (10·0), (00·2), or (10·1) textured polycrystalline structures.
The aim of this paper is first a better understanding of DC reactive magnetron sputtering and its implications, such as the hysteresis effect and the process instability. In a second part, this article is devoted to an example of specific application: Aluminium Nitride. AlN thin films have been deposited by reactive triode sputtering. We have studied the effect of the nitrogen contents in the discharge and the RF bias voltage on the growth of AlN films on Si(100) deposited by triode sputtering. Stoichiometry and crystal orientation of AlN films have been characterized by means of Fourier-transform infrared spectroscopy, X-ray diffraction and secondary electron microscopy. Dense and transparent AlN layers were obtained at high deposition rates. These films have a (002) orientation whatever the nitrogen content in the discharge, but the best crystallised ones are obtained at low value (10%). A linear relationship was observed between the AlN lattice parameter "c" (perpendicular to the substrate surface) and the in-plane compressive stress. Applying an RF bias to the substrate leads to a (100) texture, and films become amorphous. Moreover, the film's compressive stress increases up to a value of 8GPa before decreasing slowly as the bias voltage increases.
Vanadium nitride (VN) thin films were prepared by reactive DC magnetron sputtering of a vanadium target using nitrogen as reactive gas. The structural, morphological, and compositional evolution of these films is described based on hysteresis diagrams plotting the sputtering power versus nitrogen flow rate. These diagrams, measured across various cathode voltages and discharge pressures, unveil three distinct deposition regimes: metallic, intermediate, and contaminated. The microstructure of the films was found to be closely linked to the deposition regime, ranging from dense and amorphous in the metallic regime to porous and crystalline in the contaminated regime, while the composition varies from vanadium-rich to near-stoichiometric VN. Sputtered VN thin films used as electrodes for microsupercapacitors were investigated by cyclic voltammetry. Results highlight that the intermediate deposition regime, characterized by high crystallinity and porosity, yields the highest capacitance values, above 900 F cm−3. Such high volumetric capacitance is attributed to the highly porous structure and large specific surface area. In addition, in these deposition conditions, films are composed of crystalline VN with a significant amount of amorphous VOx on the surface, which allow these thin film electrodes to behave both as current collectors and pseudocapacitive electrodes. This work gives detailed insights into VN thin film microstructure and composition in reactive sputtering based on hysteresis curves. It emphasizes how we could use these curves to target specific microstructure, composition, and eventually achieve functional properties. In particular, these findings have important implications for the design and optimization of microstructured electrodes for energy storage applications.
El nitruro de aluminio es un compuesto ceramico con multitud de aplicaciones tecnologicas en muchos campos,tales como la optica, la electronica y los dispositivos resonadores. La eficiencia del AlN es altamente dependientede las condiciones experimentales de deposicion. En este articulo se analiza el efecto de la presion de trabajo enel desarrollo de tensiones residuales en su estructura. Para ello, se depositaron peliculas delgadas de AlNmediante sputtering por magnetron DC en modo reactivo con presion de trabajo variable (3-6 mTorr) sobre Si(100). Estas muestras se caracterizaron mediante medicion de curvatura de la muestra, XRD (Difraccion de RayosX), HRTEM (Microscopia Electronica de Transmision de Alta Resolucion) y SAED (Difraccion de Electrones enArea Seleccionada). Los resultados muestran que la tension residual depende del espesor de la pelicula:compresiva a bajos valores, de traccion a altos valores. Ademas, la tension residual es dependiente de la presionde trabajo, luego a mas presion menos tension residual, inhibiendo el desarrollo de la textura en el plano (00·2),vital para las aplicaciones tecnologicas. Palabras clave: AlN, sputtering reactivo DC, microscopia electronica de transmision de alta resolucion, perfilde tensiones, difraccion de rayos X. Aluminum nitride is a ceramic compound with many technological applications in several fields: optics,electronics and resonators. AlN performance is highly dependent on experimental conditions during filmdeposition. This paper focuses on the effect of working pressure on residual stress development. Thus, AlN thinfilms have been deposited with reactive DC magnetron sputtering technique under different working pressures (3-6 mTorr) on Si (100) substrates. These samples were characterized by XRD (X-Ray Diffraction), HRTEM (HighResolution Transmission Electron Microscopy) and SAED (Selected Area Electron Diffraction) techniques.Results show that residual stress is dependent on film thickness: compressive at low thicknesses, tensile at highthicknesses. Moreover, residual stress changes with the working pressure and at high pressures this stress isreduced, hampering the (00·2) texture development, crucial in technological applications. Keywords: AlN, DC reactive sputtering, high resolution transmission electron microscopy, stress profile, X-raydiffraction.
Ambipolar materials such as carbon nanotubes, graphene, or 2D transition metal chalcogenides are very attractive for a large range of applications, namely, light-emitting transistors, logic circuits, gas sensors, flash memories, and solar cells. In this work, it is shown that the nanoarchitectonics of inorganic Mo6 cluster-based iodides enable to form thin films exhibiting photophysical properties that enable their classification as new members of the restricted family of ambipolar materials. Thus, the electronic properties of the ternary iodide Cs2[{Mo6I8i}I6a] and those of thin films of the aqua-complex-based compound [{Mo6I8i}I4a(H2O)2a]·xH2O were investigated through an in-depth photoelectrochemical study. Once hole/electron pairs are created, the holes and electrons turn to be transported simultaneously in opposite directions, and their lifetimes exhibit similar values. The ambipolar properties were demonstrated via the integration of [{Mo6I8i}I4a(H2O)2a]·xH2O as light harvesters in an all-solid solar cell. A significant photoresponse with a typical diode characteristic clearly provides evidence of the simultaneous transfer and transport of holes and electrons within the [{Mo6I8i}I4a(H2O)2a]·xH2O layer. The ambipolar behavior results, on the one hand, from the confinement of electrons imposed by the nanometric size of the molecular metal clusters and, on the other hand, from the poor electronic interactions between clusters in the solid state. Such molecular structure-based layers lead naturally to an intrinsic semiconducting behavior.
