title: Photocurrent generation in carbon nanotube/cubic-phase HfO2 nanoparticle hybrid nanocomposites.
abstract: A hybrid material consisting of nonfunctionalized multiwall carbon nanotubes (MWCNTs) and cubic-phase HfO2 nanoparticles (NPs) with an average diameter of 2.6 nm has been synthesized. Free standing HfO2 NPs present unusual optical properties and a strong photoluminescence emission in the visible region, originating from surface defects. Transmission electron microscopy studies show that these NPs decorate the MWCNTs on topological defect sites. The electronic structure of the C K-edge in the nanocomposites was probed by electron energy loss spectroscopy, highlighting the key role of the MWCNT growth defects in anchoring HfO2 NPs. A combined optical emission and absorption spectroscopy approach illustrated that, in contrast to HfO2 NPs, the metallic MWCNTs do not emit light but instead expose their discrete electronic structure in the absorption spectra. The hybrid material manifests characteristic absorption features with a gradual merger of the MWCNT π-plasmon resonance band with the intrinsic defect band and fundamental edge of HfO2. The photoluminescence of the nanocomposites indicates features attributed to combined effects of charge desaturation of HfO2 surface states and charge transfer to the MWCNTs with an overall reduction of radiative recombination. Finally, photocurrent generation under UV-vis illumination suggests that a HfO2 NP/MWCNT hybrid system can be used as a flexible nanodevice for light harvesting applications.
authors.affiliation: Institute of Physics, University of Tartu, Ravila 14c, 51014 Tartu, Estonia; Department of Physics, University of Oslo. P.O. Box 1048 Blindern, 0316 Oslo, Norway.
authors.forename: Protima
authors.initials: P
authors.lastname: Rauwel
authors.affiliation: Department of Physics, University of Oslo. P.O. Box 1048 Blindern, 0316 Oslo, Norway.
authors.forename: Augustinas
authors.initials: A
authors.lastname: Galeckas
authors.affiliation: Tartu College, Tallinn University of Technology, Puiestee 78, 51008 Tartu, Estonia.
authors.forename: Martin
authors.initials: M
authors.lastname: Salumaa
authors.affiliation: IMEP-LAHC, CNRS, Université de Grenoble-Alpes, Minatec campus, 38016 Grenoble, France.
authors.forename: Frédérique
authors.initials: F
authors.lastname: Ducroquet
authors.affiliation: Tartu College, Tallinn University of Technology, Puiestee 78, 51008 Tartu, Estonia.
authors.forename: Erwan
authors.initials: E
authors.lastname: Rauwel
keywords: HfO2; carbon nanotubes; nanoparticles; photocurrent