Growth and Er-Doping of ZnO Structures by a Hydrothermal Chemical Method

• Main Authors: Wei-Chieh Yang, 楊偉傑
• Other Authors: Lih-Juann Chen
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/83459418430646311395

博士 === 國立清華大學 === 材料科學工程學系 === 96 === Zinc oxide has attracted intensive research effort in recent years, due to its unique properties and versatile applications. The design and control over size and morphology of nanometer- and micrometer-sized ZnO structures is a pressing matter of the moment to exploit novel properties and new phenomena arising from hierarchical structures. One-step synthesis of morphology-tunable ZnO 1D nanostructures was developed via a low temperature hydrothermal process using ammonia as mineralizer. Si wafer was used as a substrate for the direct growth of ZnO. Several types of morphologies, that is, shuttle-like, star-like, flower-like, dandelion-like, sheaf-like, half sheaf-like were successfully achieved by varying the reaction conditions. The growth mechanisms for these ZnO structures were discussed. Doping is one of the most efficient ways to modulate the electrical, optical and/or magnetic properties of semiconductor. A new strategy to introduce metallic dopant into ZnO structures by a wet chemical reaction is presented. Single-crystal Er-doped ZnO flower-like structures have been synthesized on ZnO-coated silicon substrate by a low temperature hydrothermal process. The Er-doped ZnO structures exhibit promising 1.54 μm photoluminescence emission for optoelectronic communication. The successful doping has been confirmed by the x-ray diffraction, transmission electron microscopy, x-ray photoemission spectroscopy and photoluminescence measurements. The achievement to introduce Er dopants into ZnO flower-like structures by the time- and cost-effective wet chemical reaction at low temperature for the first time has vast potential to scale up for possible applications. The photoluminescence properties are significantly improved compared to that reported in the literature for the Er-doped nanowires and thin films and shall be much more applicable in optical and communication devices. The flower-like structures are expected to be advantageous in serving as a multi-directional infrared emitters and/or detectors. Vertically aligned Er-doped ZnO nanorod arrays with sharp and intense 1.54 μm infrared emission have been fabricated on Si substrates through a well controlled spin-coating and annealing process. The synthesis method is advantageous for synthesizing ZnO nanostructures free from structural defects, capability for large-scale production, minimum equipment requirement and product homogeneity. Er atoms were found to incorporate into ZnO lattice from XRD, ESCA, TEM, STEM/EDS and PL measurements. The single-crystal Er-doped nanorods maintained their high microstructural quality after annealing for 4 hr at 800 ℃. The intensity of 1.54 μm infrared emission was found to be correlated with the deep level green emission. The enhanced luminescence intensity and best ever narrow wavelength distribution of Er-doped ZnO nanorod arrays at 1.54 μm emission will be conductive to applications in optoelectronic devices and optical communications.