Well-aligned IrO₂ nanocrystals

We review the results of synthesis of well-aligned IrO 2 nanocrystals (NCs) on sapphire (SA), LiNb O3 (LNO), LiTa O3 (LTO) substrates via reactive magnetron sputtering and metal-organicchemical vapor deposition. The surface morphology and structural properties of the as-deposited NCs were characterized. Field emission scanning electron microscopy micrographs reveal that NCs grown on SA(100)/LNO(100) are vertically aligned, while the NCs on SA(012)/LTO(012) and SA(110) contain singly and doubly tilted alignments, respectively, with a tilt angle of ∼35 ° from the normal to the substrates. NCs grown on SA(001) show in-plane alignment with mosaic structure. The X-ray diffraction results indicate that the NCs are (001), (101), and (100) oriented on SA(100)/LNO(100), SA(012)/LTO(012)/SA(110), and SA(001) substrates, respectively. A strong substrate effect on the alignment of the IrO 2 NCs deposition has been demonstrated. The roles of different substrates in the formation of various textures of nanocrystalline IrO 2 are studied and the possible mechanisms have been discussed.