AVS 50th International Symposium
    Nanometer Structures Tuesday Sessions
       Session NS-TuM

Paper NS-TuM2
Growth and Characterization of ZnO Nanowires

Tuesday, November 4, 2003, 8:40 am, Room 308

Session: Nanowires
Presenter: J.B. Baxter, University of California, Santa Barbara
Authors: J.B. Baxter, University of California, Santa Barbara
E.S. Aydil, University of California, Santa Barbara
Correspondent: Click to Email
ZnO is a wide band gap semiconductor with applications in UV optoelectronics, transparent conducting oxide coatings, piezoelectronics, and photovoltaics. Nanostructured ZnO can exhibit quantum confinement effects and enable applications requiring high surface area such as sensors and dye sensitized solar cells. We have grown monodisperse ZnO nanowires by chemical vapor deposition (CVD) using the organometallic precursor zinc acetylacetonate (Zn(acac)@sub 2@) in the presence of oxygen. Nanowire diameters depend on the growth conditions and range from 16 nm to 100 nm. The growth morphology depends sensitively on the substrate and the partial pressure of Zn(acac)@sub 2@. On a-plane sapphire, nanowires grow epitaxially and perpendicular to the substrate in dense arrays and with in-plane rotational order. X-ray diffraction pole figures confirm the epitaxial relationship ZnO(0001)||Al@sub 2@O@sub 3@(11-20) and ZnO(11-20)||Al@sub 2@O@sub 3@(0001). Conversely, nanowires grow on c-plane sapphire in one of three directions relative to the substrate owing to ZnO(0001)||Al@sub 2@O@sub 3@(10-14) epitaxy and the trigonal symmetry of the substrate. Controlled sublimation and delivery of the solid precursor is challenging. However, we are improving our ability to control nanowire growth by studying the evaporation and decomposition of Zn(acac)@sub 2@ using thermogravimetric analysis and mass spectrometry and by monitoring the presence of the Zn(acac)@sub 2@ with in situ Fourier transform infrared (FTIR) spectroscopy. Dense ZnO nanowires with high surface area can be grown on various oxide substrates, making them suitable for replacing the mesoporous semiconductor in dye sensitized solar cells. Single crystal ZnO nanowires offer improved conduction pathways compared to sintered nanoparticles used currently, where electron transport occurs by a hopping mechanism.