title: Broadband Omnidirectional Light Trapping in Gold-Decorated ZnO Nanopillar Arrays.
abstract: The photoluminescence (PL) and reflectivity characteristics of zinc oxide nanopillars (ZnO-NPs) grown on indium-tin-oxide (ITO)-coated glasses were investigated. The room temperature PL showed bright white-light emission for the undoped ZnO-NPs grown at 600 °C, suggesting the close relation between the optical characteristic and the growth conditions being carried out for obtaining the present ZnO-NPs. The reflectivity of the as-grown ZnO-NPs array was about ∼29% with the wavelength of the incident light ranging from 200 to 1800 nm. Nevertheless, the reflectance reduced significantly to less than 9.9% when a layer of gold (Au) was deposited on ZnO-NPs by sputtering for 5 min, corresponding to more than 65% reduction in Au-coated ZnO-NPs (Au/ZnO-NPs). Moreover, the angle-resolved reflectance measurements on the present Au/ZnO-NPs array show an omnidirectional light-trapping characteristic. These remarkable characteristics, broadband and omnidirectional light-trapping of Au/ZnO-NPs, are attributed to the extended effective optical path of the incident light due to subwavelength scattering resulting from the presence of Au nanoparticles.
authors.affiliation: Department of Physics, National Chung Hsing University , Taichung 402, Taiwan.
authors.forename: Yuan-Ming
authors.initials: YM
authors.lastname: Chang
authors.affiliation: Department of Electrophysics, National Chiao Tung University , Hsinchu 300, Taiwan.
authors.forename: Man-Ling
authors.initials: ML
authors.lastname: Lin
authors.affiliation: Department of Materials and Engineering, National Chiao Tung University , Hsinchu 300, Taiwan.
authors.forename: Tung-Yen
authors.initials: TY
authors.lastname: Lai
authors.affiliation: Department of Physics, National Chung Hsing University , Taichung 402, Taiwan.
authors.forename: Chang-Hung
authors.initials: CH
authors.lastname: Chen
authors.affiliation: Department of Materials and Engineering, National Chiao Tung University , Hsinchu 300, Taiwan.|National Synchrotron Radiation Research Center , Hsinchu 300, Taiwan.
authors.forename: Hsin-Yi
authors.initials: HY
authors.lastname: Lee
authors.affiliation: Department of Physics, National Tsing Hua University , Hsinchu 300, Taiwan.
authors.forename: Chih-Ming
authors.initials: CM
authors.lastname: Lin
authors.affiliation: Department of Materials and Engineering, National Chiao Tung University , Hsinchu 300, Taiwan.
authors.forename: Yew-Chung Sermon
authors.initials: YS
authors.lastname: Wu
authors.affiliation: Department of Physics, National Chung Hsing University , Taichung 402, Taiwan.
authors.forename: Yen-Fu
authors.initials: YF
authors.lastname: Lin
authors.affiliation: Department of Electrophysics, National Chiao Tung University , Hsinchu 300, Taiwan.
authors.forename: Jenh-Yih
authors.initials: JY
authors.lastname: Juang
keywords: ZnO; broadband; light-trapping; omnidirectional; photoluminescence; white-light emission