Selective growth of IrO₂nanorods using metalorganic chemical vapor deposition

Abstract

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.