Effect of film thickness and texture morphology on the physical properties of lead sulfide thin films

Abstract

Lead sulfide (PbS) thin films were prepared onto ultra-clean quartz substrate by the electron beam gun (EBG) evaporation method. The thicknesses of the thin films were 50, 100, 150and 200 nm. Theywere annealed at 423 K for 2 h. Field emission scanning electron microscopy (FESEM) images of the thin films showed their texture morphologyat the surface of the quartz substrate. X-ray diffraction (XRD) patterns of the thin films showed that theyhave a cubic phase and rock-salt structureafter annealing. The average crystallite size for the thin films was in the range of 32-100 nm. Optical measurements confirmed that crystalline thin films have a direct band gap that increases by decreasing the film thickness. This blue shift of the band gap of thin films compared to the bulk structure can be attributed to the quantum confinement effects in the nanoparticles. A decrease in conductivity by increasing the temperature confirmed the positive temperature coefficient of resistance in the thin films that showed the dominant conduction mechanism is via a band-like transition. The density of localized states at the Fermi level increases by increasing the film thickness. Current-voltage behavior of the thin films showed an increase in both dark current and photocurrent by increasing the crystallite size which is discussed, based on the presence of trap states and barriers in nanostructures.

Photochromic Response and Steady‐State Photoconductivity of Fibrous‐Reticulated α‐MoO3 Thin Films Prepared by Modified Spray Pyrolysis Technique

“…Consequently, the mean diameter of fibrous particles slightly increases for 761 nm to 1.013 µm by increasing the thickness of the α‐MoO 3 multilayered thin film, that is well consistent with the XRD results. The increase in particle size may be due to the increase in the preferential orientation growth occurred along the (0k0) planes, showing a well agreement with several previous works . Nevertheless, the sizes of the crystal particles measured from the SEM micrographs were found to be larger than those calculated using the XRD results, referring to polycrystalline nature.…”

“…The increase in particle size may be due to the increase in the preferential orientation growth occurred along the (0k0) planes, showing a well agreement with several previous works. [27][28][29] Nevertheless, the sizes of the crystal particles measured from the SEM micrographs were found to be larger than those calculated using the XRD results, referring to polycrystalline nature. By the inspection of the obtained micrographs at higher magnification (see Figure 6), it can be revealed that the such a fibrous particle is composed of very small primary and agglomerated granules.…”

“…Similar results have been previously reported in several works. [27,28] However, Illyaskutty et al [29] have reported that the preferential orientation shall give a lower interfacial energy and a higher nucleation rate, causing accommodation of atoms particularly in that direction (0k0).…”

CHARACTERIZATION OF PbS FILM PRODUCED BY CHEMICAL BATH DEPOSITION AT ROOM TEMPERATURE

“…PbS samples have been deposited by different methods such as electrodeposition [10], spray pyrolysis [17], SILAR [18], rf sputtering [11], chemical vapour deposition [19] and chemical bath deposition (CBD) [9,20,21]. CBD is a technique in which semiconductor films are deposited onto substrates immersed in dilute solutions.…”

“…The optical band gap of PbS film in nanocrystalline form can be widened to the visible region. PbS crystallizes in the rock salt type structure [9][10][11]. The pressure can induce a phase transition of PbS from cubic to orthorhombic [12].…”