Iridium dioxide (IrO 2 ) nanorods with pointed tips have been grown on Si(100) and transition-metal-coated-Si(100) substrates, via metal-organic chemical vapor deposition (MOCVD), using (MeCp)Ir(COD) as the source reagent. The as-deposited nanorods were characterized using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). FESEM micrographs revealed that the majority of the nanorods are a wedge shape in cross section and converge at top; occasionally several of them pack into a column of a spiral tip. The vertical alignment and packing density are significantly improved by prior deposition of a thin layer of Ti on Si. TEM and XRD results indicate that the sputtered Ti thin layer erects the nanorods in the c-axis direction. XPS spectra show that iridium in IrO 2 nanorods also exist in a higher oxidation state.

Raman spectroscopy (RS) has been used as a technique for the characterization of well-aligned IrO

We have used density functional theory (DFT) calculations to investigate the oxidation of ammonia (NH3) on a RuO2(110) surface. We characterized the possible reaction pathways for the dehydrogenation of NH x species (x = 1−3) and the formation of the oxidation products N2, NO, and H2O. The presence of oxygen atoms on coordinatively unsaturated sites (Ocus) promoted the oxidation of NH3 on the surface. The oxidation of NH3 is possible on both stoichiometric and oxygen-rich RuO2(110) surfaces; in the absence of Ocus (stoichiometric surface), however, NH3 molecules prefer desorption over oxidation. Moreover, the Ocus atoms are the major oxidants in this process; the formations of H2O and NO from bridge oxygen atoms (Obr) are both unfavorable reactions. According to our energetic analysis, in the NH x dehydrogenation pathways, H atom migration from NH2-cus to Obr has the highest barrier by 0.86 eV; it is much lower than the interaction energy of NH3 on the RuO2(110) surface. In terms of nitrogen-atom-containing products, NO, N2, and N2O are all possible products of the oxidation of NH3. The formation of the gaseous oxidation products H2O and NO is determined by their binding energies, whereas that of N2 is controlled by the diffusion of Ncus atoms on the surface. In addition, the selectivity toward the nitrogen-atom-containing products N2 and NO is dominated by the coverage of Ocus atoms on the surface; a higher coverage of Ocus atoms results in greater production of NO.

No abstract

No abstract

No abstract

Well-aligned densely-packed rutile TiO(2) nanocrystals (NCs) have been grown on sapphire (SA) (100) and (012) substrates via metal-organic chemical vapor deposition (MOCVD), using titanium-tetraisopropoxide (TTIP, Ti(OC(3)H(7))(4)) as a source reagent. The surface morphology as well as structural and spectroscopic properties of the as-deposited NCs were characterized using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected-area electron diffractometry (SAED), x-ray diffraction (XRD) and micro-Raman spectroscopy. FESEM micrographs reveal that vertically aligned NCs were grown on SA(100), whereas the NCs on the SA(012) were grown with a tilt angle of ∼33° from the normal to substrates. TEM and SAED measurements showed that the TiO(2) NCs on SA(100) with square cross section have their long axis directed along the [001] direction. The XRD results reveal TiO(2) NCs with either (002) orientation on SA(100) substrate or (101) orientation on SA(012) substrate. A strong substrate effect on the alignment of the growth of TiO(2) NCs has been demonstrated and the probable mechanism for the formation of these NCs has been discussed.

No abstract