Evolution of titanium dioxide one-dimensional nanostructures from surface-reaction-limited pulsed chemical vapor deposition

This paper reviews the recent development of surface-reaction-limited pulsed chemical vapor deposition (SPCVD) technique for the growth of TiO2 one-dimensional nanostructures. SPCVD uses separated TiCl4 and H2O precursor pulses, and the anisotropic growth of TiO2 crystals is attributed to the combined effects of surface recombination and HCl restructuring at high temperature during elongated purging time. Therefore, the crystal growth is effectively decoupled from precursor vapor concentration, which allows uniform growth of TiO2 nanorods (NRs) inside highly confined spaces. The phase of TiO2 NRs can be tuned from anatase to rutile by raising the deposition temperature. Au catalysts are able to enhance the growth rate and led to bifurcated nanowire (NW) morphology. A high density three-dimensional (3D) NW architecture was created by SPCVD growing TiO2 NRs inside dense Si NW forests. Such 3D structures offer both large surface area and excellent charge transport property, which substantially improved the efficiency of photoelectrochemical devices.