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

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 degrees 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 degrees C. The WO3 film deposited at 400 degrees C exhibits minimum band gap and maximum optical conductivity of 3.2 eV and 5.8 x 10(14) (Omega.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 degrees C. The experimental results of all SBDs indicated a linear reduction in the ideality factor (n) with a small increment in effective barrier height (Phi(B)) 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 Phi(B) of 0.71 eV were recorded for device temperature at 170 degrees C. Compared with other SBDs, the device fabricated at 400 degrees C demonstrated a better thermal stability and device performance.