Effect on Photo-Absorbance and Optical Energy-Gap of Al2O3 Thin Film After Deposition of Ag Thin Film

In the present work, the experimental fabrication of aluminium oxide (Al2O3) thin film (TF) on an n-Si substrate has been done using the E-beam physical vapour deposition technique followed by the deposition of silver (Ag) thin film on that Al2O3 TF using E-beam physical vapour deposition technique. The Field emission scanning electron microscopy (FESEM) as morphological characterization shows the top view of as-deposited Al2O3 TF/n-Si substrate and the top view of the Ag TF/Al2O3/n-Si substrate which confirms the formation of the thin film. Energy Diffraction Analysis for X-Ray (EDAX) analysis confirms the presence of desired molecules as silicon (Si), silver (Ag), aluminium (Al), and oxygen (O) on the samples. XRD analysis of both the samples reveals that the deposited Ag TF has a smaller crystallite size compared to Al2O3 TF. UV–VIS Spectroscopy analysis shows improvement in photon absorption for Ag TF/Al2O3 TF sample compared to bare Al2O3 TF sample. It was found from the Tauc Plot that the main band transition of Ag TF/Al2O3 TF is close to bandgap 3.5 eV. Similarly, the main direct band transition of Al2O3 TF was obtained close to 4.15 eV. It was found that the Ag TF/Al2O3 TF shows ~ 1.2 fold photon absorption enhancement in the visible region and ~ 1.4 fold photon absorption enhancement in the UV region compared to as-deposited Al2O3 TF under open-air room temperature. So the Ag TF/Al2O3 TF structure can be used for efficient UV–VIS photo detection purposes.