Epitaxial undoped indium oxide thin films: Structural and physical properties.

Indium oxide thin films were grown by the pulsed electron beam deposition method on c-cut sapphire substrates at 10−2 mbar oxygen pressure and temperature up to 500 1C. Such conditions lead to the formation of dense, smooth and stoichiometric In2O3 films, with the cubic bixbyite structure. Epitaxial thin films were obtained at substrate temperatures as low as 200 1C. Pole figure measurements indicate the existence of (111) oriented In2O3 crystallites with different in-plane symmetry, i.e. three-fold and six-fold symmetry. The origin of this effect may be related to the specificities of the growth method which can induce a large disorder in the oxygen network of In2O3, leading then to a six-fold symmetry in the (111) plane of the bixbyite structure. This temperature resistivity behaviour shows metallic conductivity at room temperature and a metal– semiconductor transition at low temperature for In2O3 films grown at 200 1C, while the classical semiconductor behaviour was observed for the films grown at 400 and 500 1C. A maximum mobility of 24.7 cm2/V s was measured at 200 1C, and then it falls off with improving the crystalline quality of films. The optical transparency is high (480%) in a spectral range from 500 nm to 900 nm

Effects of substrate and ambient gas on epitaxial growth indium oxide thin films

Indium oxide thin films were grown by pulsed electron beam deposition method at 500 °C on c-cut sapphire and (0 0 1) oriented LaAlO3 single crystal substrates in oxygen or argon gas. The effects of ambient gas and substrate symmetry on the growth of indium oxide thin films were studied. Stoichiometric In2O3 films are formed in oxygen, while oxygen deficient In2O2.5 films are grown in argon, with In metallic nanoclusters embedded in a In2O3 matrix (nanocomposite films). In both cases, epitaxial In2O3 films having the bixbyite phase were grown with various orientation relationships, depending upon the substrate symmetry and gas ambient (oxygen or argon). Domain matching epitaxy was used to describe the precise in-plane epitaxial film-substrate relationships. The differences in film texture were correlated to the differences in growth conditions, while the differences in the film properties were correlated to the film oxygen composition

On the relevance of large scale pulsed-laser deposition: Evidence of structural heterogeneities in ZnO thin films

Pulsed-laser deposition is known as a well-suited method for growing thin films of oxide compounds presenting a wide range of functional properties. A limitation of this method for industrial process is the very anisotropic expansion dynamics of the plasma plume, which induces difficulties to grow on large scale films with homogeneous thickness and composition. The specific aspect of the crystalline or orientation uniformity has not been investigated, despite its important role on oxide films properties. In this work, the crystalline parameters and the texture of zinc oxide films are studied as a function of position with respect to the central axis of the plasma plume. We demonstrate the existence of large non-uniformities in the films. The stoichiometry, the lattice parameter, and the distribution of crystallites orientations drastically depend on the position with respect to the plume axis, i.e., on the oblique incidence of the ablated species. The origin of these non-uniformities, in particular, the unexpected tilted orientation of the ZnO c-axis may be attributed to the combined effects of the oblique incidence and of the ratio between oxygen and zinc fluxes reaching the surface of the growing film

Effect of Interlamellar Spacing on the Monotonic Behavior of C70 Pearlitic Steel

International audienceThe effect of interlamellar spacing on monotonic behavior of C70 pearlitic steel was investigated. Tensile tests under X-ray diffraction coupled with self-consistent model have been used to identify the role of interlamellar spacing on the ferrite plasticity parameters and residual stresses. It has been established that yielding of pearlite is controlled by ferrite critical shear stresses ( τc 0α) which is higher for the smaller interlamellar spacing. Moreover, the residual stress level in ferrite is higher for the largest interlamellar spacing under the same imposed total strain. Lattice strains, measured by synchrotron X-ray diffraction, show an elastic and plastic anisotropy of ferrite crystallites and high stresses in cementite which confirm the self-consistent model calculation

UV to NIR photon conversion in Nd-doped rutile and anatase titanium dioxide films for silicon solar cell application

Undoped and Nd-doped titanium dioxide anatase and rutile films have been grown by pulsed-laser deposition at 700 °C under 0.1 mbar O2. By selecting adequate substrates, TiO2 films doped with 1, 2 or 5 at.% Nd were grown and constituted with polycrystalline rutile, highly oriented (2 0 0) rutile film, or oriented (0 0 4) anatase. An UV to NIR photon conversion is evidenced in the films. Indeed, intense and well-resolved emission lines from Nd3+ have been observed upon excitation above the TiO2 bandgap at room temperature. The sensitised emission of Nd3+ is found to be much efficient in rutile than in anatase structure. Low temperature photoluminescence measurements lead to fine resolved peaks corresponding to the Nd3+ 4f transitions with different spectral characteristic according to the host matrix used. Photoluminescence dependence temperature evidences that the light emission from Nd3+ in anatase-based films is probably influenced by the presence of self-trapped excitons or by orbital interaction. Mechanisms of sensitisation host to Nd3+ are proposed for both matrixes. Finally, the Nd dopant concentration and the microstructure of TiO2 rutile films are found to affect the photoluminescence emission intensity. Rutile film (2 0 0) oriented is the most adapted host matrix to sensitise 1 at.% Nd3+ ions for an emission around 1064 nm making such Nd-doped layers interesting for photon conversion by down shifting process

Scattering vector (h 2 k 2 l 2 ) Scattering vector (h 1 k 1 l 1 ) α α 2θ 2 t New developments of multireflection grazing incidence diffraction

Abstract. The multireflection grazing incident X-ray diffraction (MGIXD) is used to determine a stress gradient in thin surface layers (about 1-20 µm for metals). In this work two theoretical developments of this method are presented. The first procedure enables determination of c/a parameter in hexagonal polycrystalline materials exhibiting residual stresses. In the second method, the influence of stacking faults on the experimental data is considered. The results of both procedures were verified using X-rays diffraction. Introduction Multireflection grazing incidence X-ray diffraction (MGIXD) is a non-destructive method which allows performing an analysis of the heterogeneous stress field for different volumes below the surface of the sample. The penetration depth of X-ray radiation is well defined and does not change during experiment in a wide 2θ range for a given incidence angle

Study of Mechanical Behaviour of Polycrystalline Materials at the Mesoscale Using High Energy X-Ray Diffraction

International audienceOwing to its selectivity, diffraction is a powerful tool for analysing the mechanical behaviour of polycrystalline materials at the mesoscale, i.e. phase and grain scale. In situ synchrotron diffraction (transmission mode) during tensile tests and modified self-consistent elastoplastic model were used to study elastic and plastic phenomena occurring in polycrystalline specimens during deformation. The evolution of stress for grains which belong to different phases of duplex stainless steel and pearlitic steel was analyzed

UV to NIR photon conversion in Nd-doped rutile and anatase titanium dioxide films for silicon solar cell application

Undoped and Nd-doped titanium dioxide anatase and rutile films have been grown by pulsed-laser deposition at 700 °C under 0.1 mbar O2. By selecting adequate substrates, TiO2 films doped with 1, 2 or 5 at.% Nd were grown and constituted with polycrystalline rutile, highly oriented (2 0 0) rutile film, or oriented (0 0 4) anatase. An UV to NIR photon conversion is evidenced in the films. Indeed, intense and well-resolved emission lines from Nd3+ have been observed upon excitation above the TiO2 bandgap at room temperature. The sensitised emission of Nd3+ is found to be much efficient in rutile than in anatase structure. Low temperature photoluminescence measurements lead to fine resolved peaks corresponding to the Nd3+ 4f transitions with different spectral characteristic according to the host matrix used. Photoluminescence dependence temperature evidences that the light emission from Nd3+ in anatase-based films is probably influenced by the presence of self-trapped excitons or by orbital interaction. Mechanisms of sensitisation host to Nd3+ are proposed for both matrixes. Finally, the Nd dopant concentration and the microstructure of TiO2 rutile films are found to affect the photoluminescence emission intensity. Rutile film (2 0 0) oriented is the most adapted host matrix to sensitise 1 at.% Nd3+ ions for an emission around 1064 nm making such Nd-doped layers interesting for photon conversion by down shifting process

Effects of the anisotropy of pulsed energy beam deposition on ZnO thin film properties

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The nature of the crystalline phase present in gallium oxide films grown by pulsed-laser deposition on c-cut sapphire substrate has been studied. Amorphous, polycrystalline or epitaxial gallium oxide films can be obtained depending upon the oxygen pressure during the growth in the 400–500 °C temperature range. Detailed pole figure measurements on epitaxial films demonstrate that the monoclinic β-Ga2O3 phase grows epitaxially on c-cut sapphire substrates at T = 500 °C under a 10− 5 mbar oxygen pressure. Two distinct textures were evidenced, i.e., the ( 2¯01) and (101) planes of the monoclinic β-Ga2O3 phase being parallel to the c-cut sapphire substrates. The corresponding epitaxial relationships were determined and interpreted in the frame of the domain matching epitaxy. The differences in the two textures were correlated to the various atomic configurations in the ( 2¯01) and (101) planes of the monoclinic β-Ga2O3 phase