Characteristics Study of Radio Frequency Sputtered TiO2 Films on ZnO Nanorods Grown by Hydrothermal Method

In this study, we aimed at exploring a layer of radio frequency (RF) sputtered titanium dioxide (TiO2) film on a sputtered ZnO film treated by hydrothermal reaction and then conducted characterization of the film. The main objective was to discuss characteristics of the fabricated TiO2 films under conditions of different annealing temperature, film thickness, and oxygen flow rate. After measurement of four-point probe for the fabricated TiO2 films under the same film thickness or oxygen flow rate, their sheet resistance all became smaller through high-temperature annealing at 500 degrees C, and the thicker the TiO2 film was, the higher the sheet resistance was. Under conditions of fixed TiO2 film thickness and annealing temperature, with increasing oxygen flow rate, the sheet resistances of sample thin films increased initially and then decreased. The sheet resistances became highest at oxygen flow rate of 4 sccm. Results, measured from field emission scanning electron microscope (FE-SEM), showed that the structure arrangement of TiO2 nanorods was affected by TiO2 film thickness, oxygen flow rate and annealing temperature. The stacking and blending situations between nanorods became severer for higher oxygen flow rate and annealing temperature above 400 degrees C. In addition, grains formed on film surface apparently spread more outwards as the film became thicker.