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Abstract: We report the deposition and structural characterization of nanostructural RuO2 on rutile (R)-TiO2/sapphire(100) templates by reactive radio frequency magnetron sputtering. The micrographs of field-emission scanning electron microscopy and X-ray diffraction patterns of RuO2/R-TiO2 heteronanostructures indicated the growth of vertically aligned RuO2 (001) nanotubes (NTs) and/or V-shaped RuO2(101) nanowedges (NWs) on top of R-TiO2 nanorods (NRs). Transmission electron microscopy and selected-area electron diffractometry characterizations of the vertically aligned RuO2 NTs showed that the hollow RuO2 NTs with square cross section have open-end morphology with long axis directed along the [0 0 1] direction, while the V-shaped RuO2 NWs revealed that the nanowedges are crystalline RuO2 with twin plane of (101) and twin direction of at the V-junction. The probable mechanisms for the formation of well-aligned RuO2 nanocrystals on top of R-TiO2 NRs were discussed. [Copyright &y& Elsevier]

Abstract: We report the growth and characterization of coexistence of vertically aligned and twinned V-shaped RuO2 nanorods (NRs). The well-aligned RuO2 NRs were grown on top of rutile (R) phase TiO2 NRs sitting on sapphire (SA) (100) substrate via metal-organic chemical vapor deposition (MOCVD) by using bis(ethylcyclopentadienyl) ruthenium (II) and titanium-tetraisopropoxide (TTIP, Ti[OCH(CH3)2]4) as source reagents. The surface morphology, structural, and spectroscopic properties of the as-deposited nanocrystals (NCs) were characterized by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), micro-Raman spectroscopy, transmission electron microscopy (TEM) and selected-area electron diffractometry (SAED). The FESEM images and XRD patterns indicated growth of vertically aligned RuO2(001) and V-shaped RuO2(101) NRs on top of R-TiO2 NRs. The Raman spectrum indicated the formation of high quality RuO2 NCs on rutile phase of TiO2 NRs. TEM and SAED characterizations of V-shaped RuO2 NRs showed that the nanorods were crystalline RuO2 with a twin plane of (101) and twin direction of at the V-junction. The probable mechanisms for the formation of well-aligned RuO2 NRs are discussed. [Copyright &y& Elsevier]

Abstract: The self-assembled vertically aligned iridium dioxide nanotubes (IrO2 NTs) have been successfully grown on sapphire (SA)(100) and LiNbO3 (LNO)(100) substrates, via metalorganic chemical vapor deposition (MOCVD), using (MeCp)Ir(COD) as the source reagent. The surface morphology and structural properties of the as-grown NTs were characterized in detail using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected area electron diffractometry (SAD), X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). FESEM images and XRD patterns revealed that the well-aligned and single-crystalline NTs were grown normal to the substrates. TEM and SAD measurements showed that the hollow IrO2 NTs with square cross section have open-end morphology and long axis directed along the [001] direction. Analysis of the growth pattern indicated that the IrO2 NTs on SA(100) and LNO(100) grow with the orientation relationship given by IrO2(001)// SA(100), IrO2[100]// SA[010] and IrO2(001)// LNO(100), IrO2[100]// LNO[010], respectively. XPS spectra show the existence of a higher oxidation state of iridium in IrO2 NTs. The probable mechanism for the formation of the vertically aligned NTs is discussed. [Copyright &y& Elsevier]

Raman scattering (RS) and field emission scanning electron microscopy (FESEM) have been used to extract microstructural information of RuO2 nanorods (NRs) and a two-phase system comprising NRs embedded in polycrystalline matrix deposited on different substrates by the metal-organic chemical vapor deposition method. The red shifts and asymmetric broadening of the Raman line shape for the NRs are analyzed by the spatial correlation model. The deduced spatial correlation length l is found to be much smaller than that of the average size L0 estimated from the FESEM images. The Raman features for the two-phase system can be resolved into two parts: a Lorentzian line shape feature corresponding to the polycrystallite at higher frequency side and an asymmetrically broadened NRs'' signature located at lower frequency end. The volume fraction of NRs in the two-phase system can be determined from the analysis. These results demonstrate the significance of RS as a structural characterization method when used in conjunction with FESEM. [Copyright &y& Elsevier]

Abstract: We report the results of the synthesis of IrO2 nanocrystals (NCs) on sapphire (SA) substrates with different orientations via metal-organic chemical vapor deposition (MOCVD) using (MeCp)(COD)Ir as the source reagent. The surface morphology and structural properties of the as-deposited NCs were characterized using field emission scanning electron microscopy (FESEM), and X-ray diffractometry (XRD). FESEM micrographs reveal that vertically aligned NCs were grown on SA(100), the NCs on SA(012) and SA(110) contained, respectively, single- and double-aligned directions with a tilt angle of 35° from the normal to the substrates, while NCs parallel in-plane alignment were gown on SA(001). The XRD results indicate that the IrO2 NCs are (001), (101), and (100) oriented on SA(100), SA(012)/SA(110) and SA(001) substrates, respectively. A strong substrate effect on the alignment of the IrO2 NCs growth has been demonstrated and the probable mechanism for the formation of the NCs is discussed. [Copyright &y& Elsevier]

Abstract: Well-aligned 1D RuO2 nanocrystals (NCs) have been grown on sapphire (SA)(100), SA(001) and LiNbO3 (LNO)(100) substrates via reactive magnetron sputtering using a Ru metal target. The surface morphology, structural and spectroscopic properties of the as-deposited NCs are characterized using field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and micro-Raman spectroscopy (RS). FESEM micrographs show that NCs grown on SA(100)/LNO(100) are vertically aligned, while NCs grown on SA(001) show in-plane alignment with mosaic structure. The XRD results indicate that the NCs are (001) and (100) oriented on SA(100)/LNO(100) and SA(001) substrates, respectively. A strong substrate effect on the alignment of the RuO2 NCs deposition has been observed and the probable mechanism for the formation of these NCs has been discussed. The usefulness of the Raman spectroscopy as a structural characterization technique of NCs has been demonstrated. [Copyright &y& Elsevier]