Influence of metal work function and incorporation of Sr atom on WO3 thin films for MIS and MIM structured SBDs

In this work, two different structure of Cu/Sr-WO3/p-Si metal-insulator-semiconductor (MIS) and Cu/Sr-WO3/FTO metal-insulator-metal (MIM) Schottky barrier diodes (SBDs) fabricated with an insulating layer of pure tungsten trioxide (WO3) and Sr-WO3 thin films have been reported. The Sr-WO3 layer was coated separately, with different concentrations (0, 4, 8 and 12 wt %) of strontium (Sr) via jet nebulizer spray pyrolysis technique (JNSP) on the p-type silica wafer (p-Si) and fluorine doped tin oxide (FTO) substrates which are been optimized at 400 °C. The XRD analysis reveals the multiphase crystalline structures for 12 wt % of Sr-WO3 film with higher average crystallite size. FE-SEM images show the randomly oriented sub-microsized slab and seashell like structures. Higher surface roughness with improved grain size for 12 wt % of Sr-WO3 film. The presence of W, O and Sr atoms was confirmed by EDX spectra. In optical studies, Maximum absorption with minimum optical band gap was observed for 12 wt % of Sr-WO3 composite film. There was a linear increase in the electrical conductivity of the films with higher wt. % of Sr. Evidently the activation energy decreased with Sr concentration which is in accordance with the bandgap values. The fitting results of the measured I-V, reveal that MIS (SBDs) under illumination condition have minimum ideality factor (n = 2.39) and maximum barrier height (Φb = 0.57) values for higher concentration (12 wt %) of Sr film compared to MIM SBDs.