P-Type Nanostructure Pbs Thin Films Prepared By the Silar Method

Abstract

In this paper, we report on the structural, optical and electrical properties of nanocrystalline lead sulfide (PbS) thin films as a p-type semiconductor deposited on glass substrates at three different pH of the cationic precursor pH (pH = 10.22, 10.60 and 11.02) by the successive ionic layer adsorption and reaction (SILAR) method. The structure and morphology of the films are characterized by means of X-ray diffractions (XRD) patterns, micro-Raman spectroscopy, field-emission scanning electron microcopy (FE-SEM) and energy dispersive X-ray spectrometry (EDXS). The band gap and electrical properties are investigated by ultraviolet visible (UV-vis) diffuse reflectance spectroscopy and impedance spectroscopy. XRD patterns and micro-Raman spectra indicate that the deposited films have a cubic structure. EDXS data are used for analyses of chemical compositional of thin films. Micro-Raman spectra show the presence of eight vibrational active Raman modes for PbS thin films. FE-SEM images show a reduction in average grain size with the increment of pH values leads to the band gap width of the film increased from 1.73 eV to 2.37 eV whereas, the particle size decreases approximately from 133 nm to 13 nm a result of quantum confinement effect. Furthermore, room-temperature Hall measurements reveal an increase in electrical resistivity from 1.1x10(3) Omega cm to 4.8x10(6) Omega cm and a decrease in electrical conductivity 8.8x10-4 (Omega cm)(-1) to 2.1x10(-7) (Omega cm)(-1) as well as carrier mobility from 720.1 cm(2) V-1 s(-1) to 2.1 cm(2) V-1 s(-1) and carrier concentration from 1.9x10(15) cm(-3) to 4.2x10(12) cm(-3) with increasing cationic precursor pH. Hall effect measurements and hot-probe experiments show that all films have p-type conductivity.