Impact of Phase Transformation in WO3 Thin Films at Higher Temperature and its Compelling Interfacial Role in Cu/WO3/p–Si Structured Schottky Barrier Diodes

Abstract

Inter-connected network grains of tungsten trioxide (WO3) thin films were deposited on glass using a jet nebulizer spray pyrolysis (JNSP) technique by varying the substrate temperature at 350, 400, 450 and 500 °C. Phase transformation (monoclinic to orthorhombic) was observed during the film growth through X-ray diffraction (XRD) analysis. Field emission scanning electron microscope (FE-SEM) images revealed a better grain growth with smooth surface for 400 °C. The WO3 film deposited at 400 °C exhibits minimum band gap and maximum optical conductivity of 3.2 eV and 5.8 × 1014 (Ω.cm)−1. From the current-voltage (I–V) characteristics, the mean electrical conductivity is found to increase gradually and the activation energy reduced at higher substrate temperature. Cu/WO3/p–Si structured Schottky barrier diodes (SBDs) have been fabricated with different substrate temperature and it was tested under variable device temperatures ranging from 30 to 170 °C. The experimental results of all SBDs indicated a linear reduction in the ideality factor (n) with a small increment in effective barrier height (ΦB) with increase in device temperature, which is due to lateral inhomogeneity’s at the interface. Moreover, the minimum n value of 2.89 and their corresponding ΦB of 0.71 eV were recorded for device temperature at 170 °C. Compared with other SBDs, the device fabricated at 400 °C demonstrated a better thermal stability and device performance.