Growth and characterization of well-aligned densely-packed rutile TiO 2 nanocrystals on sapphire (100) and (012) substrates by reactive magnetron sputtering

Abstract

Well-aligned densely-packed rutile phase TiO 2 nanocrystals (NCs) have been grown on sapphire (100) and (012) substrates by reactive magnetron sputtering using Ti metal target. The surface morphology, structural and spectroscopic properties of the as-deposited NCs were characterized using field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and micro-Raman spectroscopy. FESEM micrographs reveal the growth of vertically aligned NCs on sapphire (100), whereas the NCs on sapphire (012) were grown with a tilt angle of ∼ 33° from the normal to substrate. The XRD results reveal TiO 2 NCs with either (002) orientation on sapphire (100) substrate or (101) orientation on sapphire (012) substrate. A strong substrate effect on the alignment of the TiO 2 NCs growth has been demonstrated and the probable mechanism for the formation of these NCs has been discussed. XPS analyses show the oxygen vs. titanium ratio of 2.0 ± 0.1 for the as-grown TiO 2 NCs. Raman spectra of NCs exhibit a slight redshift in the peak position and a small broadening in linewidth with respect to that of the bulk counterpart. The results indicate the formation of good quality of nanocrystalline rutile phase TiO 2.