Si Nanocrystals Embedded in a Silicon Oxynitride Matrix

We investigated the morphological and structural change in silicon nanostructures embedded in the silicon oxynitride matrix. The study has been carried out on thin films thermally annealed at high temperature, after deposition at 400°C by Electron Cyclotron Resonance Plasma Enhanced Chemical Vapour Deposition (ECR‐ PECVD), under different deposition parameters. Our study evidenced the existence of a well defined threshold for the silicon content in the film (around 47%), to get Si nano‐crystallization in the silicon oxynitride matrix. Both Si nano‐crystals and Si nano‐columns have been observed by TEM analysis in two samples having a similar Si content but deposited under different condition

Etude et réalisation de capteurs d'humidité (Capteur à détection optique, capteur piézoélectrique à base de couche d'oxyde de zinc)

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Effect of the annealing on the electrical and optical properties of electron beam evaporated ZnO thin films

International audienceZinc oxide thin films have been grown on (100)-oriented silicon substrate at a temperature of 100 °C by reactive e-beam evaporation. Structural, electrical and optical characteristics have been compared before and after annealing in air by measurements of X-ray diffraction, real and imaginary parts of the dielectric coefficient, refractive index and electrical resistivity. X-ray diffraction measurements have shown that ZnO films are highly c-axis-oriented with a full width at half maximum (FWMH) lower than 0.5°. The electrical resistivity increases from 10-2 Ω cm to reach a value about 109 H cm after annealing at 750 °C. The FWHM decreases after annealing treatment, which proves the crystal quality improvement. Ellipsometer measurements show the improvement of the refractive index and the real dielectric coefficient after annealing treatment at 750 °C of the ZnO films evaporated by electron beam. Atomic force microscopy shows that the surfaces of the electron beam evaporated ZnO are relatively smooth. Finally, a comparative study on structural and optical properties of the electron beam evaporated ZnO and the rf magnetron deposited one is discussed

Deposition of Zinc oxide thin films for application in Bulk Acoustic Wave resonator

International audienceHigh quality piezoelectric zinc oxide (ZnO) thin films were deposited on (I 00)-oriented silicon substrate by reactive rf magnetron sputtering for bulk acoustic wave resonator. In order to improve the ZnO thin films quality, structural and electrical characteristics have been compared before and after annealing in helium (He) by X-ray diffraction and reflection coefficient S11 measurements. Scanning electron microscopy (SEM) was used to study the crystallographic structure. A previous study has shown that a substrate temperature of 100°C, a distance between the target and the substrate of 70 mm, and a pressure of 3.35 x 10-3 Torr in argon and oxygen mixed gas atmosphere, are the optimum conditions to sputter ZnO thin films with good homogeneity and a high degree of crystallinity. These films exhibit an electrical resistivity higher than 1010 Ω cm and an energy band gap of 3.3 eV at room temperature. X-ray diffraction measurements have shown that ZnO films are highly c-axis-oriented with a full width at half maximum (FWHM) below 0.5°. The decrease of the FWHM after annealing treatment has shown the crystal quality improvement. A growth of c-axis (002)-oriented ZnO films allows predominant longitudinal wave propagation. Bulk acoustic wave (BAW) resonators have been fabricated by stacking different layers of Al/ZnO/Pt on a silicon substrate which could be used for the fabrication of humidity sensors based on the quartz microbalance principle

SnO 2 films elaborated by radio frequency (RF)magnetron sputtering as a potential TCOs alternative for organic solar cells

International audienceTransparent conducting oxides (TCOs) are crucial component of solar cells. Tin doped indium oxide (ITO) is the most employed TCO, but the scarcity and high price of indium induce a search for lower cost TCOs with equivalent properties as substitute. Tin dioxide (SnO2) films have many advantages, such as rich sources of material, low prices, and non-toxicity. SnO2 films present a high visible light transmittance, near-infrared light reflectivity, and excellent electrical properties. They also have a higher chemical and mechanical stability compared to ITO. The aim of this work is to elaborate SnO2 films by RF-magnetron sputtering in order to use them as electrodes for Organic Solar Cells (OSCs). The SnO2 films were deposited on glass, SiO2 and quartz substrates in a mixed environment of Ar and O2. XRD measurements show that the as-deposited SnO2 films are polycrystalline with cassiterite tetragonal structure. SEM analysis showed that the films are homogeneous, continuous, and nanostructured. The electrical resistivity and average optical transmittance of the samples are about 10 −3 Ω.cm and over 80%, respectively. The estimated optical band gap (Eg) is around 4.0 eV while the work function of the films is around 5.0 eV. The SnO2 films are used as electrodes for inverted OSCs, using poly(3-hexylthiophene-2,5-diyl): [6,6]phenyl-C60-butryric acid methyl ester (P3HT:PC60BM) as active layer. The device's open circuit voltage (VOC) and short circuit current density (JSC) are similar to those obtained for the inverted OSCs employing ITO as the same electrode. Even if the achieved power conversion efficiency is lower compared to the value for the reference OSC with an ITO electrode, these results are promising and place SnO2 TCO as a potential candidate to replace ITO

Polyethylenimine-Ethoxylated Interfacial Layer for Efficient Electron Collection in SnO2-Based Inverted Organic Solar Cells

In this work, we studied inverted organic solar cells based on bulk heterojunction using poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C71-butyric acid methyl ester (P3HT:PCBM) as an active layer and a novel cathode buffer bilayer consisting of tin dioxide (SnO2) combined with polyethylenimine-ethoxylated (PEIE) to overcome the limitations of the single cathode buffer layer. The combination of SnO2 with PEIE is a promising approach that improves the charge carrier collection and reduces the recombination. The efficient device, which is prepared with a cathode buffer bilayer of 20 nm SnO2 combined with 10 nm PEIE, achieved Jsc = 7.86 mA/cm2, Voc = 574 mV and PCE = 2.84%. The obtained results exceed the performances of reference solar cell using only a single cathode layer of either SnO2 or PEIE