Structural and photoluminescence properties of laser processed ZnO/carbon nanotube nanohybrids
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el Therriault Department of Mechanical Engineering, E´cole Polytechnique de Montre´al, Montreal, QC, Canada H3C 3A7 (Received 1 April 2009; accepted 28 August 2009)
Zinc oxide (ZnO)/carbon-nanotubular-structures (CNTS) nanohybrids were grown using a three-step laser process. First, an ultraviolet (UV) laser (KrF) was used to deposit Co/Ni catalyst nanoparticles (NP) directly onto SiO2/Si substrates. Second, a random network of CNTS was grown onto these Co/Ni-catalyzed substrates by using the UV-laser ablation method. Finally, ZnO nanostructures were grown onto the CNTS template by means of the CO2 laser-induced chemical liquid deposition technique. While the laterally grown CNTS mainly consist of nanotube bundles featuring a high aspect ratio (diameter of 20 nm and length of up to several microns), the ZnO nanostructures were found to consist of various morphologies including nanorods, polypods, and nanoparticles with a size as small as 2 nm. The ZnO/CNTS nanohybrids were found to exhibit a polychromatic photoluminescent (PL) emission, at room temperature, comprising a narrow near-UV band centered around 390 nm, a broad visible to near infrared band (500–900 nm), and a relatively weak emission band centered around 1000 nm. These PL results are compared to those of individual components (CNTS and ZnO) and discussed in terms of carbon defect density and possible charge transfer between the ZnO nanocrystals and the carbon nanotubes. I. INTRODUCTION
One-dimensional nanoscale materials continue to attract much attention, not only for a better understanding of the physical properties at low dimensionality, but also for their potential in nanodevice applications. Carbon nanotubes (CNT) are of particular interest because of their unique molecular geometry and of their excellent electronic, thermal, and mechanical properties.1 Recently, various carbon nanostructures have been successfully used as templates for the growth of novel hybrid nanomaterials, exhibiting highly interesting and unprecedented properties. These nanohybrids mainly consist of carbon nanostructures (mostly nanotubes) decorated by nanostructures of either metallic or semiconductor materials, such as Au, Pt, TiO2, ZnO, or SnO2. They are often obtained by various conventional chemical processing or through chemical functionalization approaches.2–8 In particular, nanohybrids consisting of carbon nanostructures decorated with ZnO nanoparticles have been shown to be promising for applications such as photocatalysts,9 field emitters,10 solar cells,11 and electrophotonic nanodevices.12
II. EXPERIMENTAL
The CNTS were directly grown on a SiO2/Si substrate by means of our recently developed “all-laser” process. The “all-laser” growth process consists of the two
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0421 J. Mater. Res., Vol. 24, No. 11, Nov 2009
http://journals.cambridge.org
In this work, we report on the growth of carbon nanotubular structures (CNTS) coated with ZnO nanostructures by laser-based proc
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