Fig. 4
Micro-structural properties [21–24]. a–c XRD patterns and d–f TEM images (inset: high-resolution TEM images and diffraction patterns) of TiO2, WO3, and ITO NHs. All as-deposited NHs are amorphous films, while they become highly crystalline after annealing (TiO2 NHs: 500 °C for 30 min, WO3 NHs: 500 °C for 1 h, ITO NHs: 550 °C for 1 min)