Intrinsic defects and their influence on the chemical and optical properties of TiO2x films

International audienceIn this work, TiO2 films produced by rf sputtering of a TiO2 target in argon and argon–oxygen plasmas were studied. The oxygen content in the feed gas was varied in a range 3–20%. The chemical composition and structure of films were characterized by Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy (XPS) and x-ray diffraction. Important information about the intrinsic defects of the films and their effects on the optical properties as well as a scheme of the energy band structure of the films could be derived from a combined use of optical spectroscopy and XPS

Influence of Nd3+ doping on the structural and near-IR photoluminescence properties of nanostructured TiO2 films

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Analog Circuit Fault Classification and Data Reduction Using PCA-ANFIS Technique Aided by K-means Clustering Approach

The paper work aims to extract effectively the fault feature information of analog integrated circuits and to improve the performance of a fault classification process. Thus, a fault classification method based on principal component analysis (PCA) and adaptive neuro fuzzy inference system classifier (ANFIS) preprocessed by K-means clustering (KMC) is proposed. To effectively extract and select fault features the traditional signal processing based on sampling technique conducts to different signature parameters. A stimulus pulse signal applied to the circuit under test (CUT) allowed us to get a reference output response. Respecting both specific sampling interval and step, the fault free and the faulty output responses are sampled to create amplitude sample features that will serve the fault classification process. The PCA employed for data reduction has lessened the computational complexity and obtaining the optimal features. Thus more than 75% of data volume decreased without loss of original information. The principal components extracted by this reduction data method have been input into ANFIS aided by KMC to obtain the best fault diagnosis results. The experimental results show a score of 100% diagnostic accuracies for the CUTs. Therefore, our approach has achieved best fault classification precision comparing to other research works

Hydrogen effect on structure and mechanical properties of ZnO films deposited in Ar/H2 plasma

In the present work the mechanical properties of the ZnO thin films deposited on Si (100) substrates, were studied using a nanoindentation. The thin films of ZnO were deposited by radiofrequency sputtering with different H2/Ar gas mixture. During the deposition the species of the plasma were in situ monitored using optical emission spectroscopy. The results showed a strong effect of H2 on film hardness and elastic modulus. Using the correlation between the elastic modulus values and materials porosity in the ceramic the porosity of the ZnO was estimated . We found an increased film porosity when H2 is added to the sputtering gas, from 4% to 16% volume. Moreover we found that the porosity could be controlled by the emission intensity ratio of atomic Argon on atomic Hydrogen

Effect of the interface layer vibration modes in enhancing thermal conductivity of nanofluids

The present paper reports on an investigation of the effect of the interface layers in enhancing thermal conductivity of Cu-Ar nanofluids. The approach is based on linear response theory combined with equilibrium molecular dynamics simulations. For a wettability parameter of 1.4 and volume fraction of 5.8%, simulation results show enhancements in thermal conductivity as high as 50% . Among others, the most salient result concerns the contribution of the vibration modes of liquid Ar atoms around Cu nanoparticles (NPs) in enhancing thermal conductivity of the nanofluid. Our findings reveal that these vibration modes coincide on a large domain of frequencies (10-50)ps-1 with those of Cu atoms of the NPs. The enhancement of the thermal conductivity was explained by the increase of vibrational mean-free paths

RF sputtering of oxide films in Ar and Ar-H2 gas mixtures: role of H incorporation in developing transparent conductive coatings

Oral presentatio

Defects and doping in oxides: case of doped TiO2 films

Oxide-based films and nanostructures have emerged as important and promising materials for a wide range of applications such as photovoltaics, photocatalysis, optoelectronics, gas sensing and electronics. To develop an appropriate understanding of the properties of these oxides, it is necessary to address the material preparation methods as well as structural and defect issues. The present work deals with oxide films synthesis processes using radio-frequency sputtering technique, the film stoichiometry control and structural defect identifying, to produce transparent and conductive films. Nb-doped titanium oxide (TiO2:Nb) thin films are considered. A comparative study of the electrical and optical properties of the Nb:TiO2 thin films in relation with the film chemical properties, structural defects and crystalline phase, the target material and the sputtering gas was made. The lowest resistivity was achieved in the range 2×10-3 -7.42×10-4 Ω.cm, which makes the used deposition method a suitable technique for the development of transparent electrodes, transferable also to large areas

RF sputtering of ZnO films in Ar and Ar-H2 gas mixtures: role of H incorporation in developing transparent conductive coatings

Fundamental and applied investigation of ZnO has been recently experiencing a renaissance due to its prospective use in various technological domains and, in particular, as transparent conductive oxide (TCO) for solar cells applications. In this respect, the present work aims to study the structural and physical properties of ZnO thin films deposited by RF sputtering. Different gas mixtures were explored. Specifically, pure Ar and Ar-H2 at various concentrations were used to grow the films on n-type Si (100) wafers and glass without external heating. The plasma chemical species were followed in function of the different gas mixture settings by optical emission spectroscopy (OES). X-ray photoelectron spectroscopy (XPS) and ATR-FTIR (Attenuated Total Reflection Fourier-Transformed Infrared) spectroscopy were used to study the bulk and surface chemical composition of the films, X-ray Diffraction (XRD) analysis allowed lattice structure and grain size determination while samples morphology was checked with a scanning electron microscope (SEM). The films were also characterized for their electrical and optical properties. The introduction of hydrogen in the plasma phase strongly affected the structural, chemical and physical properties of the films. In particular a pronounced change in the films electrical behaviour was observed which become conductive when H is added in the gas mixture ([H2]>6%). The films transparency was on the other hand maintained. By combining XPS, ATR-FTIR and OES data we could correlate the established conductivity and its variations with intentional hydrogen incorporation in the crystal structure in the form of hydroxide species