D. Vernardou

Electrochemical properties of vanadium oxide coatings grown by hydrothermal synthesis on FTO substrates

Vanadium oxide coatings were hydrothermally grown on fluorine doped tin dioxide glass substrates at 95 °C and further annealed at 100 and 300 °C. The coatings were characterized by X-ray diffraction, Raman spectroscopy, atomic force microscopy, UV-vis transmittance and cyclic voltammetry. Crystalline vanadium(V) oxide with the highest surface area ratio was observed for thermal treatment at 300 °C. In addition, the same sample presented the highest intercalation charge and enhanced durability compared with the others. The importance of achieving single-phase crystalline oxide for the improvement of the coatings performance was highlighted.

Field Emission Properties of Low-Temperature, Hydrothermally Grown Tungsten Oxide

Tungsten oxide layers have been prepared on conductive glass substrates using aqueous chemical growth from a sodium tungstate precursor at low-temperature hydrothermal conditions. The deposits were then tested as cold electron emitters. Traceable layers could be deposited only within a narrow pH range of 1.5-2 at a time length not exceeding 4 h. Transmittance in the visible spectrum was found to decrease with deposition time. The presence of both monoclinic and hexagonal phases was always detected. At the longest deposition times and highest precursor concentrations, morphologies comprise randomly oriented spikes or rods. The overall emission performance is found to improve with growth time and precursor concentration. The role of morphology on the emission properties of the films is discussed.

Hydrothermally grown β-V2O5 electrode at 95 °C

The hydrothermal growth of crystalline β-V2O5 microstructures was performed on fluorine doped tin dioxide glass substrates using oxalic acid to adjust the pH of the solution for various deposition periods. It was observed that the sample grown for 48 h at pH 2 exhibited the best electrochemical response in terms of the highest specific charge and capacitance, being 772 C g(-1) and 386 F g(-1) respectively. The importance of achieving high crystalline quality samples and increased surface area toward the improvement of the electrochemical performance of β-V2O5 is highlighted.

Advancements, Challenges and Prospects of Chemical Vapour Pressure at Atmospheric Pressure on Vanadium Dioxide Structures

Vanadium (IV) oxide (VO2) layers have received extensive interest for applications in smart windows to batteries and gas sensors due to the multi-phases of the oxide. Among the methods utilized for their growth, chemical vapour deposition is a technology that is proven to be industrially competitive because of its simplicity when performed at atmospheric pressure (APCVD). APCVD’s success has shown that it is possible to create tough and stable materials in which their stoichiometry may be precisely controlled. Initially, we give a brief overview of the basic processes taking place during this procedure. Then, we present recent progress on experimental procedures for isolating different polymorphs of VO2. We outline emerging techniques and processes that yield in optimum characteristics for potentially useful layers. Finally, we discuss the possibility to grow 2D VO2 by APCVD.