Tailoring physical properties and evaluating photosensing performance of lead sulfide thin films using AACVD

Controlling the deposition temperature is an effective method for tailoring the physical properties of lead sulfide (PbS) thin films, which are essential for photo-sensing devices. In this study, PbS films were deposited using a single-source precursor of lead xanthate via the aerosol-assisted chemical vapor deposition (AACVD) technique. The deposition temperatures were varied at 200, 250, and 300 °C, while all other parameters remained constant. Various diagnostic techniques were employed to analyze the films' properties. Thermogravimetric analysis (TGA) indicated significant weight loss at 131 °C. X-ray diffraction (XRD) confirmed the formation of cubic PbS films in the galena phase, with alignment along the (200) direction across all temperatures. The crystallite size, determined using the Halder-Wagner equation, decreased with increasing temperature. Additionally, the lattice constant decreased as deposition temperature increased, with micro-strain values shifting from 1.03 to -0.93, indicating a transition from tensile to compressive strain. Field emission scanning electron microscopy (FE-SEM) revealed that higher deposition temperatures produced more regular grain shapes, achieving complete cubic morphology at 300 °C. Average grain sizes were estimated to be 161 nm, 250 nm, and 292 nm corresponding to the respective deposition temperatures. Band gap energies measured were 2.24 eV at 200 °C, 2.21 eV at 250 °C, and returning to 2.24 eV at 300 °C. The conductivity type of PbS films transitioned from p-type at 200 °C to n-type at higher temperatures. Activation energies were found to be 0.198 eV, 0.151 eV, and 0.211 eV for films deposited at 200 °C, 250 °C, and 300 °C, respectively. The photo-sensing properties of all films were evaluated at wavelengths of 397.5 nm and 459.5 nm under applied potentials of 0.2 V, 0.4 V, and 0.6 V. The rise time was observed to be within a few seconds, while the decay time was notably longer.