Structural and photoluminescence properties of laser processed ZnO/carbon nanotube nanohybrids

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 SiO ₂/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 CO ₂ 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.