Influence of the oxygen partial pressure on the growth and optical properties of RF-sputtered anatase TiO2 thin films

Titanium dioxide (TiO2) films with thicknesses around 300 nm were deposited on glass substrates by reactive radio frequency (RF) magnetron sputtering at constant RF sputtering power (200 W), high sputtering pressure and room temperature. The effects of the oxygen presence on the growth and properties of the films were investigated using mixtures of Ar and O2 with different O2/(Ar + O2) ratios (from 0.0 to 0.3) during the sample deposition. The crystalline properties and surface morphology were characterized using X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. The optical properties were studied by ultraviolet–visible–near infrared (UV–Vis–NIR) spectroscopy, and the refractive index and the thickness of the samples were obtained using the Swanepoel method. The obtained results indicate that all the TiO2 films grew with an anatase phase and with an improved crystallinity at O2/(Ar + O2) = 0.2. However, AFM studies show that the grain size and surface roughness decrease as the O2/(Ar + O2) ratio increases from 0.0 to 0.3. Moreover, a maximum refractive index was obtained for the sample prepared at O2/(Ar + O2) = 0.2

Influence of the oxygen partial pressure on the growth and optical properties of RF-sputtered anatase TiO2 thin films

Titanium dioxide (TiO2) films with thicknesses around 300 nm were deposited on glass substrates by reactive radio frequency (RF) magnetron sputtering at constant RF sputtering power (200 W), high sputtering pressure and room temperature. The effects of the oxygen presence on the growth and properties of the films were investigated using mixtures of Ar and O2 with different O2/(Ar + O2) ratios (from 0.0 to 0.3) during the sample deposition. The crystalline properties and surface morphology were characterized using X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. The optical properties were studied by ultraviolet–visible–near infrared (UV–Vis–NIR) spectroscopy, and the refractive index and the thickness of the samples were obtained using the Swanepoel method. The obtained results indicate that all the TiO2 films grew with an anatase phase and with an improved crystallinity at O2/(Ar + O2) = 0.2. However, AFM studies show that the grain size and surface roughness decrease as the O2/(Ar + O2) ratio increases from 0.0 to 0.3. Moreover, a maximum refractive index was obtained for the sample prepared at O2/(Ar + O2) = 0.2. Keywords: TiO2 films, RF reactive magnetron sputtering, XRD, AFM, Swanepoel metho

Titanium vanadium nitride electrode for micro-supercapacitors

International audienceHere we report on the synthesis of binary transition metal nitride electrodes based on titanium vanadium nitride (TiVN) thin films. These films were deposited by a method compatible with micro-electronic processes which consists of DC co-sputtering of vanadium (V) and titanium (Ti) targets. TiVN films with different Ti/V ratio were deposited. A dependence of the capacitance and the cycling stability with the Ti/V atomic ratio in the films was established. While V rich sample exhibits a Faradic behavior that limits its cycling ability despite a high areal and volumetric capacity, the addition of Ti in the film drastically improves the cycling ability with virtually no fade in capacitance after 10,000 cycles. Furthermore, a 1.1 Ti/V ratio leads to an areal capacitance up to 15 mF·cm− 2 in 1 M KOH electrolyte solution. Such electrodes shed light on the use of binary transition metal nitrides as candidate electrodes for micro-supercapacitor

Electrodes based on nano-tree-like vanadium nitride and carbon nanotubes for micro-supercapacitors

International audienceVanadium nitride (VN) was deposited by DC-sputtering on a vertically aligned carbon nanotube (CNTs) template for the purpose of nano-structuration. This led to the fabrication of hierarchically composite electrodes consisting of porous and nanostructured VN grown on vertically aligned CNTs in a nano-tree-like configuration for micro-supercapacitor application. The electrodes show excellent performance with an areal capacitance as high as 37.5 mF cm−2 at a scan rate of 2 mV s−1 in a 0.5 M K2SO4 mild electrolyte solution. Furthermore, the capacitance decay was only 15% after 20,000 consecutive cycles. Moreover, the capacitance was found to increase with VN deposit thickness. The X-ray photoelectron spectroscopy analyses of the electrodes before and after cycling suggest that the oxide layers that form at the VN surface is the responsible for the redox energy storage in this material. Such electrodes can compete with other transition metal nitride based electrodes for micro-supercapacitors. © 201

AlN film thickness effect on photoluminescence properties of AlN/carbon nanotubes shell/core nanostructures for deep ultra-violet optoelectronic devices

International audienceAluminum nitride (AlN) nanostructures are very attractive in various optoelectronic applications such as deep ultraviolet light emitting devices. The fabrication of these AlN nanostructures with good crystalline quality and compatibility in line with other micro-fabrication processes has significant importance for practical applications. AlN films of different thickness values were deposited via DC reactive magnetron sputtering over vertically aligned multiwalled carbon nanotube (CNTs) arrays to obtAln AlN/CNTs vertically-aligned shell/core nanostructure assembly. Such hybrid nanostructures were characterized using scanning electron microscope, transmission electron microscope, X-ray diffraction, Raman spectroscopy and time-resolved photoluminescence spectroscope (TR-PL) techniques. The results indicated that AlN/CNTs have a nanorods structure morphology with good AlN crystalline quality. The PL measurements revealed a maximum increase in the luminescent intensity of the exciton band in case of AlN/CNTs with 600 nm thick AlN layer, which is many orders of magnitude higher than that of AlN film produced over silicon substrate. It is anticipated that synergistic effects of CNTs and AlN through an increase in the specific surface area and oxygen-induced defects cause enhancement in the photoluminescence properties, making these hybrid nanostructures a promising candidate for optoelectronic applications