Nanocrystalline PbS Thin Films Research Articles

Optical and photoconductivity properties of Mn doped nanocrystalline PbS thin films deposited by chemical bath deposition method

Mn doped nanocrystalline PbS thin films were deposited onto glass substrates by chemical bath deposition (CBD) method. All the deposited thin films were found to be crystalline having cubic phase structure. The optical properties of the Mn doped nanocrystalline PbS thin films have been studied. They have high absorbance in the UV-visible region. The linear nature of (αhν)2 vs (hν) plots of PbS thin films confirmed that the transition is direct and the optical band gap energy of PbS films is found to increase from 1.90 eV to 2.28 eV with decreasing crystallite size from 21 nm to 11 nm and the optical band gap values are higher than the bulk value (0.40 eV). The optical band gap of Mn doped PbS films are found to increase with increase in dopant concentrations. The Photoconductive rise time and decay time determined from the prepared films are found to decrease with increase in doping concentrations.

Effects of Thickness on Optical and Structural Properties of Lead Sulphide(PbS) Thin Film Prepared by Chemical Bath Deposition

Nanocrystalline PbS thin films were deposited on glass substrates with various deposition times using chemical bath deposition technique. PbS thin films were prepared by using a solution of Lead nitrate and thiourea by using NaOH salt as a complexing agent and ammonia solution as a pH adjuster at 65 0 C. The study was carried out for thickness in the range of (0.16-1.03m). The structural properties were carried out by X-ray diffraction (XRD). The X-ray diffraction patterns reveal that the films exhibit the cubic face centered structure. The crystalline sizes of the films increased with increasing film thickness. The morphological properties were studied by SEM and showed that films were well adherent to the substrate, uniform, small crystal size and covered the entire substrate surface completely. The optical properties of these films have been studied and show that PbS thin films have the values of energy gap varied between (0.88-1.34 eV) with increasing film thickness. Keywords: XRD, band gap, PbS thin film DOI: 10.7176/JNSR/13-9-01 Publication date: May 31 st 2022

Structural and Optical Properties of Nanocrystalline Pbs Thin Films Prepared by Microwave-Assisted Chemical Bath Deposition

Structural and Optical Properties of Nanocrystalline Pbs Thin Films Prepared by Microwave-Assisted Chemical Bath Deposition

Effects of Thickness on Optical and Structural Properties of Lead Sulphide (PbS) Thin Film Prepared by Chemical Bath Deposition (CBD)

Nanocrystalline PbS thin films were deposited on glass substrates with various deposition times using chemical bath deposition technique. PbS thin films were prepared by using a solution of Lead nitrate and thiourea by using NaOH salt as a complexing agent and ammonia solution as a pH adjuster at 65 0 C. The study was carried out for thickness in the range of (0.16-1.03m). The structural properties were carried out by X-ray diffraction (XRD). The X-ray diffraction patterns reveal that the films exhibit the cubic face centered structure. The crystalline sizes of the films increased with increasing film thickness. The morphological properties were studied by SEM and showed that films were well adherent to the substrate, uniform, small crystal size and covered the entire substrate surface completely. The optical properties of these films have been studied and show that PbS thin films have the values of energy gap varied between (0.88-1.34 eV) with increasing film thickness. Keywords: CBD, XRD, band gap, PbS thin film DOI: 10.7176/CMR/12-7-01 Publication date: September 30 th 2020

Electrical and photo-electrical properties of spin-coated nanocrystalline PbS thin films evaluated using thermoelectric effect

Nanocrystalline (NC) PbS films have the potential to be used as tunable photodetectors and solar cells, but their electrical properties are not yet understood. The electrical and photo-electrical properties of NC PbS thin films deposited by spin-coating have been investigated. The films are p-type and photoconducting. Electrical conductivity (σ), thermoelectric power (αth), hole concentration (p), and mobility (μ) of the films in dark and under illumination were measured in the temperature range of 77–300 K. These parameters behaved differently in the low temperature region (LTR) of 77–150 K and the high temperature region (HTR) of 250–300 K. In LTR, dark p was constant (∼1014 cm−3) while thermally activated in HTR. In LTR, dark μ varied as T1.5 due to impurity scattering, while in HTR, μ varied as T−(4.2–9.2) due to lattice scattering. Under light, p was ∼1018 cm−3 in LTR while thermal quenching occurred in HTR suggesting the existence of electron traps below the conduction band, which act as sensitization centers. The quenching energy was 130–90 meV, which varied with film thickness. The μ of illuminated PbS films decreased with temperature as T−n due to lattice scattering. The NC PbS films showed high photoconductivity in LTR with a light to dark conductivity ratio of 103. Photoconductivity is explained on the basis of trapping of minority carriers by sensitization centers.

Effect of thickness on structural and optical properties of spin-coated nanocrystalline PbS thin films

This paper reports the influence of thickness on structural and optical properties of spin-coated NC PbS films. NC PbS films were deposited on glass by spin-coating precursor layers from molecular ink and then heating in air at 100 °C. Thicknesses of films investigated were 250–500 nm deposited by layer-by-layer coating. The films were shiny, smooth, uniform and continuous. X-ray diffraction (XRD) studies show that the films are nanocrystalline with crystallite size of about 10 nm irrespective of thickness. Atomic force microscopy (AFM) show that as thickness increases, roughness increases from 1.4 to 5.1 nm and grain sizes increases from 9 to 30 nm. Optical parameters of PbS films were determined by measuring transmittance and reflectance spectra from 400 to 2400 nm. The absorption coefficient of films were better than 105 cm−1. The band gap of films decreased from 2.02 to 1.64 eV and Urbach energy decreased from 0.32 to 0.205 eV as the thickness increased. The refractive indices (at 900 nm) of NC PbS films increased from 1.44 to 2.17 while extinction coefficient (at 500 nm) also increased from 0.54 to 1.04 as the film thickness increased from 250 to 500 nm. Interestingly, the refractive indices of NC PbS films is much below the bulk value of 4.2. The real and imaginary dielectric constants of films also increased with increase in thickness. Thickness variation of dispersion parameters of refractive indices were evaluated with Wemple and DiDomenico single oscillator model. Oscillator energy decreased from 3.9 to 2.7 eV while dispersion energy was conststant at 3.8 eV.

AFM investigation and optical band gap study of chemically deposited PbS thin films

The interest into deposition of nanocrystalline PbS thin films, the potential of designing and tailoring both the topographical features and the band gap energy (Eg) by controlling growth parameters, has significant technological importance. Nanocrystalline thin films of lead sulfide were grown onto glass substrates by chemical bath deposition (CBD) method. The experiments were carried out by varying deposition temperature. We report on the modification of structural and optical properties as a function of deposition temperature. The morphological changes of the films were analyzed by using SEM and AFM. AFM was also used to calculate average roughness of the films. XRD spectra indicated preferred growth of cubic phase of PbS films in (200) direction with increasing deposition time. Optical properties have been studied by UV-Spectrophotometer. From the diffused reflectance spectra we have calculated the optical Eg shift from 0.649-0.636 eV with increasing deposition time.

Nanocrystalline PbS Thin Films as Photodetectors

Nanocrystalline PbS Thin Films as Photodetectors

Direct-Coated Photoconducting Nanocrystalline PbS Thin Films with Tunable Band Gap

Nanocrystalline PbS thin films are deposited on glass by direct coating from a precursor solution of lead acetate and thiourea in methanol. A single coating has a thickness of 50 nm and greater thicknesses are obtained from layer by layer deposition. The films are smooth and shiny with roughness (rms) of about 1.5 nm. X-ray diffraction studies show that films are cubic PbS with crystallite size about 10 nm. The films are p-type with dark electrical conductivities in the range of 0.4–0.5 S/cm. These films are basically photoconducting. Photoconductivity monotonically increases with increase in thickness. The band gap of the films strongly depends on the thickness of the films. The band gap decreases from 2.4 eV to 1.6 eV as the thickness is increased from 50 nm to 450 nm. The tunability of the band gap is useful for technical applications, such as solar cells and photodetectors.

Electrical characteristics of (n)Si/(p)PbS heterojunction prepared by chemical bath deposition technique

Zn doped nanocrystalline PbS thin films is deposited on single crystal (n)-Si substrate by chemical bath deposition to form (n)Si/(p)PbS heterojunction structure. In order to study the current transport mechanism in (n)Si/(p)PbS heterojunction, the forward current–voltage characteristics is measured within the temperature 300 K – 340 K and capacitance–voltage characteristics is measured at a frequency of 1 kHz at 300 K. The forward current is greatly enhanced with increasing temperature whereas the reverse current is increased nominally. Junction parameters such as ideality factors, barrier heights, saturation current density, Richardson constant, etc. are determined from the I–V characteristics. The ideality factors are found to decrease with increase in temperature. The J–V characteristics under illumination showed poor photovoltaic effect of the junction. The higher value of ideality factor and poor photovoltaic conversion efficiency are due to the presence of interfacial layer, large series resistance and high defect density.

Preparation and Characterization of Nanocrystalline PbS Thin Films Produced by Chemical Bath Deposition

Preparation and Characterization of Nanocrystalline PbS Thin Films Produced by Chemical Bath Deposition

Effect of TEA on photoluminescence properties of PbS nanocrystalline thin films

In this work, the PbS nanocrystalline thin films were prepared by chemical bath deposition method on the glass and unpolished Si(100) substrates. Triethanolamine was used as additive in the aqueous solution, which resulted in the enhancement of the luminescence of nanocrystalline PbS thin films. The introduction of triethanolamine reduced the grain size and increased the optical band gap of the PbS nanoparticles. The crystalline size of PbS films deposited at two different bath temperatures of 25 °C (PbS-25) and 40 °C (PbS-40) and at different deposition times was estimated to be around 5–50 nm by XRD analyses. The films at 60 °C (PbS-60) were prepared and studied. The structural, morphological and optical properties of the obtained films were investigated. The energy-dispersive X-ray of the typical PbS film was presented, which confirmed the formation of PbS. The mechanism of growth of the PbS crystallites at different bath temperatures was described. The confinement was reflected in absorption and photoluminescence spectra. The variation of the photoluminescence intensity of PbS nanocrystals with triethanolamine molarity, deposition time and bath temperature was investigated. The PbS thin films were found to exhibit PL in both the ultraviolet and visible regions via quantum size effects, surface states and excitation wavelength variation. The luminescence of Si(100) substrate and PbS nanocrystalline films deposited on Si(100) were compared, and the results revealed that the PbS nanocrystals altered and notably enhanced the emission features of the Si(100) substrate. The multi-peak fitting using Gaussian function was employed for the photoluminescence spectrum of PbS on Si(100) substrate.

Effect of lead ion concentration on the structural and optical properties of nano-crystalline PbS thin films

PbS thin films have received considerable attention because of their potential applications in opto-electronics applications. Spontaneous reaction of lead acetate and thiourea in aqueous hydrazine hydrate has been used for depositing PbS thin films on glass substrates. Structural and optical properties of PbS thin films are greatly influenced by the morality of the reactants and crystal defects in the lattice. Our work focuses on the variation in lead ion concentration and its effect on the structural and optical properties of PbS thin films. The deposited films were analyzed using XRD, SEM, spectrophotometer and dark resistance measurement. XRD patterns indicated the formation of major phase of nano crystalline PbS with minor presence of lead oxide phase. We also noticed that peak intensity ratio of I111/I200 varied by changing the Pb ion concentration. The film thickness and dark resistance increased whereas optical band gap decreased with the decreasing Pb ion concentration. SEM scans showed that the grain size is less than 100 nm and is not affected by varying Pb ion concentration.

Comparative studies on the structural, morphological, optical, and electrical properties of nanocrystalline PbS thin films grown by chemical bath deposition using two different bath compositions

High-quality lead sulfide (PbS) thin films were synthesized by chemical bath deposition from two baths with different compositions. One of them (bath-І) contained an aqueous solution of lead acetate, thiourea, sodium hydroxide, and the second (bath-ІІ) had additional triethanolamine. The introduction of triethanolamine reduced the grain size and increased the optical band gap of the PbS nanoparticles. The structure, morphology, and optical properties of the obtained films were investigated and compared with respect to the deposition time. X-ray diffraction data were used to obtain the crystallite size, lattice constant, and strain of the films. Atomic force microscopy results show that the roughness and rms-surface slope of the samples obtained from bath-I (PbS-I) were higher than those of bath-II (PbS-II) samples. PbS thin films with high reflectance (~61%) in the near-infrared region, which is important in our solar system, were obtained. The band gap, extinction coefficient, and refractive index of the samples were calculated. Furthermore, Raman analysis was performed and electrical properties of the samples were studied.

Synthesis and Study of the Structural and Electrical Conductivity for Nanocrystalline PbS Thin Films

Synthesis and Study of the Structural and Electrical Conductivity for Nanocrystalline PbS Thin Films

Structural and optical properties of nanocrystalline lead sulfide thin films prepared by microwave-assisted chemical bath deposition

Nanocrystalline PbS thin films have been successfully deposited on glass substrate from lead nitrate (Pb2+ ions) and thiourea (S2− ions) precursors using MACB technique. The effects of molar concentration (0.02, 0.05, 0.075 and 0.1M) on the structure and microstructure evolution were studied using X-ray diffraction (XRD), scanning electron microscopy, and atomic force microscopy. The optical properties were investigated using UV–vis spectrophotometer. Crystal size values obtained from XRD were compared with these calculated using atomic force microscopy (AFM). The values of optical band gaps were found to decrease as the ion source molar concentration increase.

Retracted] Chemical Bath Deposition of PbS:Hg2+ Nanocrystalline Thin Films

Nanocrystalline PbS thin films were prepared by Chemical Bath Deposition (CBD) at 40 ± 2°C onto glass substrates and their structural and optical properties modified by in‐situ doping with Hg. The morphological changes of the layers were analyzed using SEM and the X‐rays spectra showing growth on the zinc blende (ZB) face. The grain size determined by using X‐rays spectra for undoped samples was found to be ~36 nm, whereas with the doped sample was 32–20 nm. Optical absorption spectra were used to calculate the Eg, showing a shift in the range 1.4–2.4 eV. Raman spectroscopy exhibited an absorption band ~135 cm−1 displaying only a PbS ZB structure.

Growth of Nanocrystalline PbS Thin Films by Solid-Vapor Deposition

Solidvapor deposition was used to synthesize nanocrystalline PbS thin films on a Si (100) substrate. Lead sulfide (PbS) powder was first prepared and then heated to 1050 °C in a tube furnace. The resulting vapor was carried to the substrate zone by an argon flow. The structure of the nanocrystalline PbS thin films was determined by X-ray diffraction (XRD). The grain size of the PbS thin films and powder was also estimated by XRD. The surface morphology and stoichiometric ratio of these ingots were observed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy. The SEM image revealed that the film had a uniform surface morphology over the entire substrate. The optical absorbance of the deposited films and powder were measured by Fourier-transform infrared spectroscopy. The optical band gap Eg of the samples was calculated using the Tauc formula. The absorption of the thin films was found to be higher than that of the powder and lower for the entire wavenumber range (15005000 nm). The Eg values of the films determined were 3647 nm (0.34 eV), and that of the powder was 3100 nm (0.40 eV).

Characterization of Nanocrystalline Lead Sulphide Thin Films Prepared by Chemical Bath Deposition Technique

Nanocrystalline PbS thin films were deposited on clean glass substrates by chemical bath deposition technique using lead acetate and thiourea as Pb2+ and S2− ions source, respectively. PbS films of five different molarities (0.05–0.150M) were prepared at pH (10.5 and 11) and deposition temperature (318 and 333 K). The structural characterization of the films was carried out by X-ray diffraction (XRD), X-ray fluorescence (XRF) and scanning electron microscopy (SEM).The structural parameters such as crystallite size, lattice constant, dislocation density and micro strain have been evaluated from the XRD spectra. The average crystallite sizes were found between 13 and 21 nm. XRF gave the presence of Pb and S in the prepared films. The surface morphology of the films was known from the SEM photographs.

Characterization of nanocrystalline PbS thin films prepared using microwave-assisted chemical bath deposition

Nanocrystalline lead sulfide (PbS) thin films were synthesized on glass substrates using microwave-assisted chemical bath deposition (CBD) method. Various deposition periods of time ranging from 30 to 120min were used. Results demonstrated that the thickness of the thin films increased with longer deposition time. X-ray diffraction (XRD) measurement revealed that all thin films have cubic rock salt (NaCl) type structure. The surface morphology studied using scanning electron microscopy (SEM) showed that the films have uniform surface morphology over the entire substrate and were of good quality. AFM images confirm that the films have a smooth surface with good adherence to the substrate, a narrow particle size distribution, and that the surface roughness increased with increasing deposition time. Energy gap Eg decreases as the deposition time increases. Electrical measurements revealed that all films were p-type and that the conductivity decreased as the deposition time increased.