Growth and characterization of vertically aligned IrO2 one dimensional nanocrystals on LiNbO3 (100) via reactive sputtering

We report the preparation of vertically aligned one dimensional (1D) IrO2 nanocrystals (NCs) on LiNbO3 (100) by reactive magnetron sputtering using Ir metal target. The effects of sputtering conditions such as distance between gun and substrate, pressure, power of radio frequency generator and substrate temperature have been presented and discussed. The surface morphology, structural and spectroscopic properties of the as-grown NCs were characterized in detail using field emission scanning electron microscopy (FESEM), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and micro-Raman scattering. FESEM micrographs reveal that vertically aligned NCs were grown on LiNbO3 (100) substrates. The XRD results indicate that the IrO2 NCs are (002) oriented on LiNbO3 (100). The probable mechanism for the formation of the vertically aligned 1D NCs has been discussed. The XPS examination shows the existence of extra features at higher-binding-energy sites of Ir 4f and O 1s which is a common property for IrO2 1D NCs. The red shift and asymmetric broadening of Raman lineshape have been analyzed and attributed to both the size effect and residual stress.