Selective growth of IrO₂ nanorods using metalorganic chemical vapor deposition

Area-selective growth of iridium dioxide (IrO₂) nanorods has been demonstrated via metalorganic chemical vapor deposition (MOCVD) using precursor (methylcyclopentadienyl)(1,5-cyclooctadiene)Ir on a sapphire (012) or (100) substrate which consists of patterned SiO₂ as the nongrowth surface. The optimal substrate temperature for selective growth is 450 ± 10°C at a chamber pressure of 20 mbar. Orientation of nanorods is dictated by the in-plane epitaxial relation between the IrO₂ crystal and sapphire, along with the IrO₂ growth habit in the [001] direction. The photolithography method is shown to be a superior patterning method since it gives a better resolution in preserving rod orientation at the growth and nongrowth boundary zone. The initial growth of IrO₂ nuclei is also studied. Selectivity, rod orientation, and other morphological features of the nanorod forest can find their origins in nucleation behavior during initial growth.