Béatrice Doisneau

Synthesis and physical properties of ZnO/CdTe core shell nanowires grown by low-cost deposition methods

Vertically aligned ZnO/CdTe core/shell nanowire arrays have been grown by low-cost deposition techniques. ZnO nanowires have a wurtzite structure and are c-axis oriented. The CdTe shell completely covers ZnO nanowires and consists of nanograins, which are slightly oriented along the ⟨111⟩ direction owing to a grain growth process driven by surface energy minimization. Their nucleation follows the Volmer–Weber growth mechanism: in particular, island coalescence results in the generation of high tensile stress, which significantly reduces the CdTe optical band gap. Furthermore, both ZnO and CdTe exhibit excitonic emission bands around 3.36 eV and 1.56 eV, respectively.

Morphological and electrical characterization of ZnO nanocomposites in dye-sensitized solar cells

ZnO nanocomposites were fabricated as photoanodes for dye-sensitized solar cells. ZnO nanowires grown by catalyst-free metal-organic chemical vapor deposition were uniformly covered with ZnO nanoparticles by chemical bath deposition. ZnO nanocomposites exhibit the highest cell efficiency of 2.44% with a 16.7 mA/cm2 short circuit current density due to a higher specific surface area as compared to bare ZnO nanowires. The relatively low open circuit voltage of 0.48 V is associated with a significant decrease in the electron effective life time as shown by electrochemical impedance spectroscopy measurements, pointing out the importance to control the interface quality in dye-sensitized solar cells.

PEALD ZrO2 Films Deposition on TiN and Si Substrates

a STMicroelectronics 850 rue Jean Monnet 38926 Crolles, France. b SIMaP, Grenoble-INP-CNRS-UJF, 1130 rue de la piscine 38402 Saint Martin d’Heres, France. c CMTC, Grenoble-INP, 1260 rue de la piscine 38402 Saint Martin d’Heres, France. d ESRF 6 rue Jules Horowitz 38043 Grenoble, France. e CEA-LETI, Minatec 17 rue des Martyrs 38054 Grenoble, France. f LPCML, Universite Lyon 1 UMR 5620, CNRS, 10 rue Andre-Marie Ampere 69622 Villeurbanne, France.

Zinc oxide nanostructured material for dye sensitized solar cells

ZnO nanowires have been grown either by Metal Organic Chemical Vapor Deposition (MOCVD) or Chemical Bath Deposition (CBD). MOCVD allows to tune the wire diameter under a wider range whereas CBD gives rise to better oriented wires. Nanowires can be covered by CBD with Layered Hydroxide Zinc Acetate (LHZA), which is thermally decomposed into 20nm ZnO particles to achieve nanowire-nanoparticle composite structure. Dye sensitized solar cells (DSSC) performed with this type of composite structure are compared to nanowires or nanoparticles based DSSC. Composite cell is a compromise between high specific surface area provided by nanoparticles and direct conduction path thanks to nanowires. Measurement of I–V curves shows that using composite material can increase the short circuit current of the cell.

The quest towards epitaxial BaMgF4 thin films: exploring MOCVD as a chemical scalable approach for the deposition of complex metal fluoride films

Conventional and Pulsed Liquid Injection MOCVD processes (C-MOCVD and PLI-MOCVD) have been explored as synthetic routes for the growth of BaMgF4 on Si (100) and single crystalline SrTiO3 (100) substrates. For the two applied approaches, the volatile, thermally stable β-diketonate complexes Ba(hfa)2tetraglyme and Mg(hfa)2(diglyme)2(H2O)2 have been used as single precursors (C-MOCVD) or as a solution multimetal source (PLI-MOCVD). Structural characterization through X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM) analyses confirmed the formation of epitaxial BaMgF4 films on SrTiO3 substrates. Energy dispersive X-ray (EDX) analyses have been used to confirm composition and purity of deposited films. The impact of process parameters on film properties has been addressed, highlighting the strong influence of precursor ratio, deposition temperature and oxygen partial pressure on composition, microstructure and morphology of the films. Both methods appear well suited for the growth of the BaMgF4 phase, but while PLI-MOCVD yields a more straightforward control of the precursor composition that reflects on film stoichiometry, C-MOCVD provides easier control of the degree of texturing as a function of temperature.