Intrinsic Properties of Multi-Layer TiO2/V2O5/TiO2 Coatings Prepared via E-Beam Evaporation

Abstract

Nanocomposite multi-layer TiO2/V2O5/TiO2 thin films were prepared via electron-beam evaporation using high-purity targets (TiO2 and V2O5 purity > 99.9%) at substrate temperatures of 270 °C (TiO2) and 25 °C (V2O5) 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 TiO2 mono-layer was ~3.49 eV, whereas that of the multi-layer TiO2/V2O5/TiO2 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 TiO2/V2O5/TiO2 thin films suggest their efficient use as a solar water heater system.

Comparison of Sputtered and Evaporated Vanadium Pentoxide Thin Films for Resistive Microbolometer Application

“…V 2 O 5 thin film possesses an orthorhombic structure with a unit cell volume of 0.092 nm 3 . The broad diffractions are showing that the crystallite size of V 2 O 5 lies in the nanometer scale range.…”

“…IR sensors, e.g., bolometers, thermopiles and pyroelectric sensors are highly sensitive detectors that are, nowadays, easily produced due to developments in manufacturing processes [2]. In general, microbolometers consist of highly sensitive materials that are able to detect insignificant changes in temperature by drastically changing their electrical resistivity [3,4]. They are made of three basic layers; the heat-insulating layer, the thermally sensitive layer, and the thermal absorber layer [5].…”