Formation of vanadium oxides with various morphologies by chemical vapor deposition

Abstract We reported the formation of vanadium oxides with various morphologies, including V 2 O 5 rods, VO x microspheres, VO 2 microblocks etc., by chemical vapor deposition using vanadyl acetylacetonate (VO(acac) 2 ) powder as a vanadium precursor. The obtained samples were characterized by scanning electron microscopy (SEM), Raman scattering and X-ray diffraction (XRD). Results revealed that the morphologies and microstructures of vanadium oxides were significantly dependent on the depositing temperature. V 2 O 5 rods with a diameter of ∼250 nm, VO x microstructure with V 5+ and V 4+ cations and VO 2 microblocks were obtained at the depositing temperature of 500, 450–250 and 150 °C, respectively. VO 2 structures were formed at the beginning of growth process, and V 4+ cations were partially oxidized to V 5+ cations at the higher depositing temperature (250–450 °C). Various morphologies of VO x were attributed to the mixed microstructure of V 2 O 5 and VO 2 . The difference between V 4+ O and V 5+ O bonds induced the distortion and various structures in VO x . When the depositing temperature was as high as 500 °C, most of the V 4+ cations were oxidized to V 5+ cations and V 2 O 5 rods were obtained.