Study of structural and electro-optical properties of Al/PbO/p-Si thin films produced by CBD and SILAR methods

In this study, Al/PbO/p-Si thin films were produced using two highly economical and practical methods: chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR). The structural and optical properties of the produced thin films were examined in detail and the results were compared according to the production methods. XRD analysis revealed the prominent presence of the tetragonal (alpha-PbO) and orthorhombic (beta-PbO) phases of PbO. The crystallite sizes of PbO thin films were calculated using Debye-Scherrer and Williamson-Hall methods. It was determined that the PbO thin film produced by the CBD method had larger average crystallite sizes compared to those produced by the SILAR method (CBD D = 42.93 nm, SILAR D = 35.67 nm from Scherrer's formula). The formation of the PbO2 crystal phase in the PbO thin film produced by the SILAR method caused the lattice strain to increase from 2.93 x 10-4 to 4.03 x 10-4. It was also observed that the thin film produced by the SILAR method was better crystallized and exhibited less amorphization than the CBD method. The PbO thin film produced by the CBD method exhibited a tightly bound, porous structure composed of rod-shaped or irregularly layered grains. SEM results showed that the surface of the PbO thin film produced by the SILAR method was found to consist of dense micro-spherical aggregates, and had smaller porosities and particle formations than that produced by the CBD method. From the UV-visible light transmittance spectra, the band gap energy was determined for CBD and SILAR and found to be 3.61 eV and 3.75 eV, respectively. Moreover, the electrical and interface properties of the Al/PbO/p-Si MOS Schottky diode, formed using CBD and SILAR methods on p-type silicon (p-Si) substrate, were analyzed in detail. Important parameters such as current-voltage (I-V), differential resistance (Rj), and interface state density (Nss) were examined under dark and illuminated conditions. As a novel result, the electronic performance of the Al/PbO/p-Si MOS Schottky diode produced by the SILAR method is higher than that produced by the CBD method.