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Communication Dans Un Congrès Année : 2001

Gas phase ZnO nanoclusters and structural, optical and lasing properties of corresponding nanostructured thin films

Résumé

In this communication we present a pulsed laser ablation (PLA) method of synthesis of high quality nanostructured thin films for optoelectronics applications. Contrary to the well-known epitaxial (atom by atom) growth of ZnO at low oxygen pressure we use a cluster-assisted synthesis of ZnO films. Gas phase ZnO nanoclusters have been formed during conventional Ultra Violet (λ=193 nm) PLA of sintered ZnO targets into binary, O2/He or O2/Ar, gas mixtures. The role of the first gas is as oxidizing agent and the second one is used for nanocluster cooling and reducing their velocity during condensation and deposition stage. Fundamental aspects of nanoclusters synthesis have been analyzed by reflectron mass spectrometry (MS) and optical time resolved spectroscopy of the laser induced plume together with structural analysis of solid films by X-ray diffraction, HRTEM and AFM microscopy. Optical and lasing properties of films have been studied by conventional photoluminescence and excitation spectroscopy using femtosecond lasers. From MS measurements we show that oxide clusters ZnxOy are already formed in vacuum. Where x is the number of Zn atoms, clusters up to x = 20 have been registered. The concentration of these clusters strongly increase during synthesis in the surrounding gas. We clearly observed four distinct populations: the major one with composition ZnxOx-1 and three minor, oxygen rich, population ZnxOx+1 , ZnxOx+2 and ZnxOx+3 The relative concentration of these initial clusters within the laser induced plume determines the final properties of the film. Using MS and optical time of flight observation of cluster expansion dynamics we discuss the origin of different components of the plume. The total yield of gas formed nanoclusters shows a well pronounced maximum as a function of laser fluence. From all of these results, using the relation between nucleation rate, plume temperature and number of ejected particles, we show a way of optimizing of the deposition process Cluster assisted deposition of ZnO produces homogeneous nanostructured films with cluster size between 5-15 nm , depending on the conditions of the synthesis. All deposits show oriented nanostructures with C axis ┴ to the substrate, where the substrate were electronic grade c-Al2O3, SiO2, Si[111] or Si[100]. ZnO films formed under optimized conditions exhibit excellent optical properties with a narrow exciton luminescence band and a strongly reduced defect green band. Finally we demonstrate room temperature ultraviolet laser emission from nanostructured ZnO. Both excitonexciton and electron-hole plasma emission regimes were observed.
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Dates et versions

hal-01895779 , version 1 (15-10-2018)

Identifiants

  • HAL Id : hal-01895779 , version 1

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Wladimir Marine, Alexander V. Bulgakov, Dmitry K. Nelson, Igor Ozerov, Marc Sentis. Gas phase ZnO nanoclusters and structural, optical and lasing properties of corresponding nanostructured thin films. 6th International Conference on Laser Ablation, Oct 2001, Tsukuba, Japan. ⟨hal-01895779⟩
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