Pulsed electrodeposition and characterisation of tungsten diselenide thin films

The transition metal semiconductor tungsten diselenide (WSe2) films have been pulsed electrodeposited on titanium and SnO2:F coated glass substrates from an ammoniacal solution of H2WO4 and SeO2 under galvanostatic conditions. The initial layers of the film were of Se followed by an increasing amount of W in the deposit. Some intermediate layers have a composition equivalent to tungsten diselenide. An induced co-deposition mechanism for the WSe2 film deposition has been suggested. The growth kinetics of the film was studied and the deposition parameters such as electrolyte concentration, bath temperature, deposition time, deposition current, pH of the electrolyte and duty cycle of the current are optimized. X-ray diffraction (XRD) analysis showed the presence of highly textured WSe2 film with hexagonal structure. EDAX spectrum shows that the films are stoichiometric and SEM pictures show uniform, pinhole free and uniform granular shaped grains. The optical absorption spectra show that the material has an indirect band gap value of 1.42 eV. The electrical conductivity measurements were carried out and the semiconductor parameters such as activation energy, trapped energy state and the barrier height were evaluated.