Abstract
Nanocomposite multi-layer TiO
2
/V
2
O
5
/TiO
2
thin films were prepared via electron-beam evaporation using high-purity targets (TiO
2
and V
2
O
5
purity > 99.9%) at substrate temperatures of 270 °C (TiO
2
) and 25 °C (V
2
O
5
) under a partial pressure of oxygen of 2 × 10
−4
mbar to maintain the stoichiometry. Rutherford backscattering spectrometry was used to confirm the layer structure and the optimal stoichiometry of the thin films, with a particle size of 20 to 40 nm. The thin films showed an optical transmittance of ~78% in the visible region and a reflectance of ~90% in the infrared. A decrease in transmittance was observed due to the greater cumulative thickness of the three layers and multiple reflections at the interface of the layers. The optical bandgap of the TiO
2
mono-layer was ~3.49 eV, whereas that of the multi-layer TiO
2
/V
2
O
5
/TiO
2
reached ~3.51 eV. The increase in the optical bandgap was due to the inter-diffusion of the layers at an elevated substrate temperature during the deposition. The intrinsic, structural, and morphological features of the TiO
2
/V
2
O
5
/TiO
2
thin films suggest their efficient use as a solar water heater system.