abstract:Vertically aligned densely packed anatase- and rutile-phase TiO2 nanocrystals (NCs) have been grown by metal-organic chemical vapor deposition (MOCVD) on sapphire (SA)(100) substrates under different conditions, using titanium-tetraisopropoxide (Ti(OC3H7)4) as a source reagent. The surface morphology, structural and spectroscopic properties of the as-deposited NCs were characterized in detail using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and micro-Raman scattering. FESEM and TEM micrographs reveal the growth of vertically aligned NCs on SA(100) substrates. The XRD results indicate that the anatase- and rutile-TiO2 NCs are, respectively, (110) and (001) oriented on SA(100). Raman spectra show that pure anatase- and rutile- phase have been deposited. The roles of different growth conditions in the formation of different phases of the vertically aligned TiO2 NCs are studied and the probable mechanisms have been discussed.