PbS Thin Films Research Articles

Improved microstructure and performance of PbS thin films via in-situ thermal decomposition of lead xanthate precursors using self-assembling monolayer

Microstructure control is critical to achieve thin film-based devices with high performance. The surface properties of the substrates on which thin films grow are expected to greatly influence the morphology and the resulting performance. Generally, homogeneous, dense and highly crystalline films are required. However, “island” like structures are usually obtained mainly due to the non-uniform nucleation. In this article, the self-assembling monolayer (SAM) strategy was applied to efficiently realize the uniform nucleation and modulate the microstructure of lead sulfide (PbS) thin films, which were fabricated on the modified ZnO-coated substrates with 3-mercaptopropionic acid (MPA) SAM via in-situ thermal decomposition of lead xanthate precursors. The results showed that PbS thin films with reduced pin-holes and uniform crystalline grains were fabricated with the incorporation of MPA SAM. More importantly, PbS thin films modulated by MPA showed better photoelectric response.

Tuning the physical properties of PbS thin films towards optoelectronic applications through Ni doping

Ni-doped PbS (PbS:Ni) thin films were deposited on glass substrates by cost-effective spray pyrolysis technique with different concentrations of Ni (0, 2, 4, 6 and 8 at.%). XRD studies reveal that all the films exhibit face centered cubic structure. The preferential orientation of the undoped PbS film is along the (2 0 0) plane and for the doped films the preferential orientation is along the (1 1 1) plane. Optical studies show that the film transparency increases with increase in Ni doping concentration and the optical band gap exhibit a red shift from 2.26eV to 2.06eV. Electrical studies show that all the as deposited PbS:Ni thin films have resistivity in the order of 10−1Ω-cm. Raman studies reveal that the peak at 161cm−1 might have been originated from the combination of longitudinal and transverse acoustic phonon modes in PbS crystals. Increased transparency and nominal resistivity values obtained make PbS:Ni thin films suitable for optoelectronic applications especially in solar cells.

Synthesis and characterization of highly ordered nanosized PbS thin films: modified silar

Synthesis and characterization of highly ordered nanosized PbS thin films: modified silar

Ligand Background of the Reaction Mixture as a Factor of the CdS – PbS thin Films Formation by Chemical Bath Deposition

Ligand Background of the Reaction Mixture as a Factor of the CdS – PbS thin Films Formation by Chemical Bath Deposition

RETRACTED: Synthesis, morphological, optical and structural properties of PbSSe2− nanocrystals

Abstract Herein Se 2− -doped PbS thin films obtained by using the green chemical bath approach are reported. Morphological, optical and structural properties were investigated by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and optical absorption. Three impurity levels were prepared by changing the relative volume of the solution containing Se 2− ions in the PbS growing solution. XRD showed growth of all films with the zinc-blende phase. Changes in the grain size (∼27–14 nm) and band gap energy (∼1.4–2.24 eV) were observed. The absorbance in doped films, showing excitonic peaks are due to higher energy transitions from 1 S e → 1 S h . Gibbs energy calculation for the Se 2− doping PbS process was also investigated.

Structural, optical and electrical properties of PbS and PbSe quantum dot thin films

PbS and PbSe were prepared by hot injection method. The powders were used for preparing the corresponding films by using thermal evaporation technique. The structural, optical and electrical properties of PbS and PbSe thin films were investigated. The structural properties of PbS and PbSe were investigated by X-ray diffraction, transmission electron microscopy and energy dispersive X-ray techniques (EDX). PbS and PbSe films were found to have cubic rock salt structure. The particles size ranged from 1.32 to 2.26 nm for PbS and 1.28–2.48 nm for PbSe. EDX results showed that PbS films have rich sulphur content, while PbSe films have rich lead content. The optical constants (absorption coefficient and the refractive index) of the films were determined in the wavelength range 200–2500 nm. The optical energy band gap of PbS and PbSe films was determined as 3.25 and 2.20 eV, respectively. The refractive index, the optical dielectric constant and the ratio of charge carriers concentration to its effective mass were determined. The electrical resistivity, charge carriers concentration and carriers mobility of PbS at room temperature were determined as 0.55 Ω cm, 1.7 × 1016 cm−3 and 656 cm2 V−1 s−1, respectively, and for PbSe films they were determined as 0.4 Ω cm, 9 × 1015 cm−3 and 1735 cm2 V−1 s−1, respectively. These electrical parameters were investigated as a function of temperature.

Characterization of PbS thin films obtained by chemical bath at low temperature using sodium citrate as complexing agent

ABSTRACTThe deposition of PbS thin films by the chemical bath deposition method using sodium citrate as non-toxic complexing agent is presented. As-deposited PbS films and those annealed at 200 and 300 °C in argon atmosphere were formed by tightly compact spherical particles homogeneously distributed along the substrates. The XRD analysis shows that all the films had a galena type cubic crystalline structure. The crystallite size of the as-deposited film was 17 nm which decreased to 14 nm when the film was annealed to 300 °C. Thermal treatments to the films produced a shift of the optical band gap from 1.34 to 1.49 eV. Furthermore, the as-deposited PbS films were photosensitive showing a conductivity of 10-2 Ω-1 cm-1 under illumination. Such a conductivity increased to 10-1 Ω-1 cm-1 with the thermal treatment at 200 °C. The evaluation of the PbS film using a CdS thin film partner as window in the solar cell configuration showed an open circuit voltage of 88 mV and a short current density of 3.5 mA/cm2.

Effect of double substitutions of Cd and Cu on optical band gap and electrical properties of non-colloidal PbS thin films

Controllable band gap has been pursued to absorb a proper range of light by p-type absorber semiconductors for better performance photovoltaic devices. Here we introduce double substitutions with Cd and Cu for non-colloidal p-type PbS thin films to cover a broader range of optical band gap from 1.22 to 1.78 eV. Thin films of (Pb1−xCdx)1−yCuyS (x = 0–0.3 and y = 0–0.3) were grown by a single step chemical bath deposition process at a low temperature of 70 °C. The incorporation of Cd resulted in a wider band gap but changed the type of semiconductor into n-type above x = 0.2. Only the proper substitutions with both Cd and Cu induced an optimal band gap of 1.63 eV, which means a substantial improvement compared to 1.22 eV for pure PbS thin film, while maintaining p-type conductivity. Interestingly, excessive Cu substitutions beyond y = 0.2 inhibited crystallization significantly and generated an undesirably high carrier concentration.

Swift heavy ion-irradiation effects on microstructure, surface morphology and optical properties of PbS thin films

Chemically deposited PbS nanocrystalline thin films are irradiated by 100 MeV Si8+ swift heavy ions of fluences 1 × 1011, 1 × 1012 and 1 × 1013 ions/cm2. Detailed investigation on the effects of irradiation on microstructure is carried out by X-ray diffraction line profile analysis applying Williamson–Hall and modified Williamson–Hall methods, and transmission electron microscope observation, while atomic force microscope is used for studying the modifications in surface morphology. The band gaps are obtained from electronic absorption spectroscopy measurements, and photoluminescence spectra are recorded by spectrofluorometer. The pristine and irradiated films are polycrystalline in nature with spherical crystallites having face-centered cubic phase. The crystallite size of the pristine film is 20 nm, while films irradiated with ion fluences 1 × 1011, 1 × 1012 and 1 × 1013 ions/cm2 are 21, 20 and 20 nm, respectively. The lattice strain (dislocation density) of the pristine film is 8.9 × 10−3 (6.6 × 1016 m−2), while films irradiated with ion fluences 1 × 1011, 1 × 1012 and 1 × 1013 ions/cm2 are 8.6 × 10−3 (6.1 × 1016 m−2), 8.7 × 10−3 (6.4 × 1016 m−2) and 9.1 × 10−3 (7.0 × 1016 m−2), respectively. The dislocations present in both the pristine and irradiated films are edge in nature. The surface morphology changes significantly with elongation of the particles, increase in particle size and interparticle separation and slight decrease in rms roughness after irradiation. The band gap of the pristine film is 2.51 eV which remains unaltered after irradiation. Photoluminescence intensity increases significantly after irradiation which can be useful in enhancing the performance of different photonic devices such as light-emitting diodes, lasers and luminescence-based sensors.

Structural and Optical Characterization of Chemically Deposited PbS Thin Films

PbS thin films were deposited on glass substrates by a chemical bath deposition method. The effect of varying the film thickness on the structural and optical properties has been investigated. XRD analysis reveals the crystallinity of the deposited PbS films with (200) preferred crystal orientation. Increasing the film thickness enhances the crystallinity of the films as well as decreases the strain and dislocation density. The surface morphology features were dramatically changed from small spherical grains to bead-like shape. The absence of impurities in the deposited films was confirmed by energy dispersive x-ray spectrometry (EDX) measurements. The optical constants of the deposited films were calculated and a small decrease in the band gap energy was observed with increasing the film thickness.

Nanocrystalline PbS Thin Films as Photodetectors

Nanocrystalline PbS Thin Films as Photodetectors

Influencing the structural, microstructural and optical properties of PbS nanocrystalline thin films by Mg2+ doping

The aim of the current work is study the effect of Mg2+ doping (0–4%) on lead sulfide (PbS) thin films prepared using a simplest and cost effective chemical bath deposition (CBD) technique on glass substrates at ambient temperature and pressure. The effect of Mg2+ content on structural, morphological and optical properties of PbS thin films was studied. Powder X-ray diffraction and Atomic Force Microscopic results showed that all the deposited thin films exhibits both nanostructured and polycrystalline nature with cubic structure. The remarkable effect on optical transmittance and band gap was observed due to Mg2+ doping for all the films. The optical energy band gap values were found to enhance with increasing the Mg2+ content in PbS thin films. Further, the refractive index was calculated and a relationship with energy band gap was investigated and also the high frequency dielectric constant (ε∞) was determined using the energy band gap values as a function of the Mg2+ content.

Chemically synthesized PbS Nano particulate thin films for a rapid NO2 gas sensor

Abstract Rapid NO2 gas sensor has been developed based on PbS nanoparticulate thin films synthesized by Successive Ionic Layer Adsorption and Reaction (SILAR) method at different precursor concentrations. The structural and morphological properties were investigated by means of X-ray diffraction and field emission scanning electron microscope. NO2 gas sensing properties of PbS thin films deposited at different concentrations were tested. PbS film with 0.25 M precursor concentration showed the highest sensitivity. In order to optimize the operating temperature, the sensitivity of the sensor to 50 ppm NO2 gas was measured at different operating temperatures, from 50 to 200 °C. The gas sensitivity increased with an increase in operating temperature and achieved the maximum value at 150 °C, followed by a decrease in sensitivity with further increase of the operating temperature. The sensitivity was about 35 % for 50 ppm NO2 at 150 °C with rapid response time of 6 s. T90 and T10 recovery time was 97 s at this gas concentration.

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.

Deposition of morphology-tailored PbS thin films by surfactant-enhanced aerosol assisted chemical vapor deposition

In this work, we report the results of deposition of PbS thin films using single molecular precursor, bis(O-isobutylxanthato)lead(II), in the presence of additives namely: sodium dodecyl sulfate (SDS), Tween and Triton x-100, via aerosol assisted chemical vapor deposition (AACVD). The as-deposited PbS thin films are highly crystalline and exhibited superior adhesion to glass substrates. Powder X-ray diffraction (XRD) analysis confirmed the formation of pure cubic phase of PbS. Thin films deposited using 0.4mM Triton X-100 as additive resulted in wire like structures while 0.8mM Triton X-100 deposited thin films comprised of predominantly shoe shaped structures. Further, increase in concentration (1.2mM) of Triton X-100 deposited films having rod like morphology. The scanning electron microscopy (SEM) confirmed that in the presence of SDS, thin films consist of spherical shaped crystallites. Energy dispersive X-ray spectroscopy (EDX) and X-ray photon electron microscopy (XPS) of as-deposited PbS thin films was used to study chemical composition of thin films.

Sulfide precursor concentration and lead source effect on PbS thin films properties

Lead sulfide (PbS) thin films were synthesized using chemical bath deposition (CBD). Bath solutions are formed of various concentrations of thiourea, sulfide source, ranged from 0.6 to 1.2 M and two different salts as Pb source (lead acetate and lead nitrate). From the growth mechanism, we inferred that PbS is formed through the ion by ion process when using acetate lead source, while, using nitrate source yields to films growth through the complex-decomposition process. Due to the difference in the involved growth process, lead acetate produces films with larger crystallite size (from 4 to 16 nm), smooth and dense films. However, lead nitrate produces rough films with smaller crystallite size (from 1 to 4 nm). Increasing the thiourea concentration results in crystallinity improvement when using lead acetate and, oppositely, in crystallinity degradation when using lead nitrate. Due to the quantum effect caused by the small crystallite sizes, the films optical gap is varied from 0.5 to 0.9 eV.

Synthesis and Optical Properties of Lead Sulfide And Copper Sulfide Thin Films Deposited By Chemical Bath Deposition Method

We report the synthesis and Optical properties of crystalline Copper sulfide and Lead sulfide thin films deposited on glass substrate using the chemical bath deposition method [CBD] at room temperature for 22 hours 23 minutes and 72 hours respectively. Copper sulfide was synthesized using copper sulphate and thiourea, while Lead nitrate and thiourea were used for the synthesis of lead sulfide thin films. Optical properties of the thin films were studied by spectrophotometer in the wavelength range of 200 nm - 800 nm. Band gap [Eg], absorbance [A] and absorption coefficients [α] were examined as a function of wavelength and photon energy. Further analysis revealed that Cu2S and PbS thin films had a band gap of 2.324 eV and 2.586 eV respectively, suitable for solar cell applications.

Temperature dependent behaviour of lead sulfide quantum dot solar cells and films

The temperature dependent behaviour of PbS QD solar cells and thin films was investigated, and guidelines for further improvement of the power conversion efficiency are given.

Enhanced SWIR absorption in chemical bath deposited PbS thin films alloyed with thorium and oxygen

We report on chemically deposited thin films of PbS alloyed with thorium. Material properties, including the optical band gap, are shown to strongly depend on film composition, presenting a clear bowing behavior and enhanced SWIR absorption.

In situ monitoring the role of citrate in chemical bath deposition of PbS thin films

We report the formation of size tunable PbS nanocubes induced by the presence of trisodium citrate during growth of PbS thin films by chemical bath deposition. The presence of citrate induces growth by the cluster mechanism which is monitored by XRD and HRSEM, along with real time light scattering and optical absorption measurements.