Enhanced Absorption and Photoemission from TiO2 Nanowire/Graphene Oxide Thin-Film Heterostructure

Vertically oriented TiO2 nanowires (NWs) have been fabricated on graphene oxide (GO) thin film (TF) using a catalytic free growth technique called glancing-angle deposition. GO TF was spin coated on Si substrate at different rotation speeds and the surface roughness measured by atomic force microscopy. Field-emission scanning electron microscopy confirmed formation of a heterostructure consisting of GO TF with thickness of similar to 300 nm and TiO2 NWs with length of similar to 800 nm. Selected-area electron diffraction analysis in transmission electron microscopy showed that the TiO2 NWs grown on the GO TF were amorphous in nature, as confirmed by x-ray diffraction analysis. A bandgap close to similar to 4.1 eV was obtained for GO TF, whereas a main band transition edge at 3.3 eV was obtained for a TiO2 NW/GO TF heterostructure sample, related to TiO2. Two subband transitions at 2.9 eV and 2.4 eV were also observed for the heterostructure sample, corresponding to oxygen and Ti3+ defect transitions for the TiO2 NWs. Enhanced photoluminescence and absorption were observed for the heterostructure sample as compared with the GO TF sample.