Chemical bath deposition of high structural and morphological quality PbSe thin films with potential optoelectronic properties for infrared detection applications

Abstract

Lead selenide (PbSe) thin films deposited by aqueous-based chemical methods have recently reached considerable importance for the production of different low cost and good quality optoelectronic devices. Applications in infrared devices as well as in low cost photovoltaic technologies as efficient absorbent layers have been extensively studied. In this work, the synthesis of homogeneous, polycrystalline, low-roughness, electrically conductive and narrow band gap PbSe thin films by using Chemical Bath Deposition (CBD) on glass substrates is reported. The effects of using different NaOH concentrations on the films physical and chemical properties were studied. Structural analysis realized by X-Ray Diffraction (XRD) technique showed the polycrystalline nature of the films, particularly observing a preferred <100> texture. Atomic Force Microscopy (AFM) studies revealed a compact and homogeneous growth of the thin films. A well-defined microstructure and low roughness (varying between 5 and 35 [nm]) were generally observed. Scanning Electron Microscopy (SEM) imaging studies showed the good growth quality of the thin films, observing well-defined film-to-substrate interfaces. Film thickness values between 138 ± 9 and 277 ± 20 [nm] were estimated. Chemical composition analysis realized by Energy Dispersive X-Ray Spectroscopy (EDS) exposed the non-stoichiometric nature of the PbSe films. An atomic concentration predominance of Se with respect to Pb in all samples was observed, suggesting a possible p-type conductivity. Infrared spectrophotometry measurements indicated energy band gaps in the Mid-Infrared Range (MIR), estimating values from 0.326 up to 0.393 [eV]. The thin films generally presented high electrical conductivities with respect to the typical ranges for semiconductors, estimating values in the order of 101 [(Ω·cm)−1]. Results show that the low cost and simple synthesis CBD based procedures can be used to produce high structural and morphological quality PbSe thin films with attractive optoelectronic properties (narrow band gap and electrically conductive) for the potential development of devices in infrared detection industry.