Growth control and characterization of vertically aligned IrO2 nanorods

Iridium dioxide (IrO2) 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 IrO2 nanorods also exist in a higher oxidation state.