Electrical and optical properties of highly oriented nanocrystalline vanadium pentoxide

摘要

Highly oriented nanocrystalline hydrated vanadium pentoxide, V_2O_5.nH_2O, were grown epitaxially on a glass substrate along the c-axis to form a film of 200 nm thick. The films were prepared by dissolving V_2O_5 powder in hydrogen peroxide, H_2O_2, solution. X-ray diffraction, transmission electron micrograph and electron diffraction were used to identify the structure of the obtained nanocrystals. Homogenous nanocrystals of 7.0 ± 1.0 nm in size were obtained and were closed packed and are distributed evenly. Electrical conductivity and thermoelectric power were measured in the temperature range 300-480 K for the as prepared films parallel to the substrate surface; i.e. normal to the c-axis. The obtained results showed an n-type semiconducting behavior within the whole temperature range. It is also clear to see that a reversible abnormality at about 340 K is realized during the cooling electrical conductivity measurements. On the other hand, optical transmission and reflection were used to evaluate different optical parameters such as; optical band gap, nature of donor levels and different absorption bands parameters. Both the electrical and optical data are correlated and accordingly the conduction mechanism is verified. Electronic parameters such as effective mass, carriers' type and concentration and drift mobility were evaluated.