Search

Generation of hydrogen fuel via the photocatalytic water splitting mechanism using semiconductor nanoparticles under sunlight irradiation is highly important. Moreover, the development of nanophotocatalysts for polluted water treatment is significant. In this regard, we synthesized CdS, CdS:Er (2 at%), and CdS:Er (4 at%) nanoparticles by a simple reflux route. According to the comprehensive structural analysis, Er3+ ions were incorporated into the CdS host lattice at the substitutional and interstitial sites, without altering the original structure. Photocatalytic measurements revealed that the degradation efficiency of 2 at% Er-doped CdS nanoparticles reached 100% within 100 min of visible light irradiation. In addition, CdS:Er (2 at%) nanoparticles exhibited enhanced photocatalytic hydrogen generation ability under simulated sunlight irradiation. Hence, from the obtained results, we concluded that CdS:Er (2 at%) nanoparticles are promising semiconductor photocatalytic materials for wastewater treatment as well as hydrogen fuel generation.

The design and development of one-dimensional nanostructures have been gaining considerable interest owing to the exceptional optoelectronic and catalytic properties of these structures. Thus, herein, wurtzite phase polycrystalline one-dimensional nanostructures of pristine and Co-substituted ZnO nanorods were fabricated using the hydrothermal method. Co ion substitution into the ZnO lattice was confirmed by structural analysis. Furthermore, an X-ray photoelectron spectroscopic survey suggested that Co ion inclusion in the host Zn2+ site occurred with a Co2+ oxidization state. The quenching of band gap with the Co inclusion into ZnO host sites was determined through optical studies. Room temperature hysteresis curves demonstrated the superparamagnetic nature of the synthesized ZnO and Co-doped ZnO nanorods. The photocatalytic activity of the synthesized nanorods was estimated by the exclusion of Rhodamine-B degradation under artificial solar light illumination. Distinctly, 66.5% photocatalytic degradation efficiency was achieved in Co-doped ZnO nanorods over 100 min; however, only 64.13% efficiency was observed for bare ZnO nanorods over 120 min. The enhanced photocatalytic activity in the Co-doped ZnO sample could be due to the creation of huge trapping sites, massive surface area, and generation and consequent separation of electron and hole pairs.

Lead sulfide is a potential infrared (IR) photodetector material because of its favorable optoelectronic properties. The physical and chemical properties of PbS can be modified by a systematic doping of elements. In this study, we have doped 1–3 at% of Sn into PbS by a chemical bath deposition method. The undoped PbS films exhibited cubic crystal structure with a lattice parameter of $$\hbox{a} = 0.594\,\hbox{nm}$$ , an uneven grain growth, a direct optical band gap of 0.44 eV and a hole mobility of $$8.9\,\hbox{cm}^{2}\,\hbox{V}^{-1}\,\hbox{s}^{-1}$$ . The Sn-doping has improved the microstructure and slightly decreased the band gap of PbS. The hole mobility of PbS films has increased to $$20\,\hbox{cm}^{2}\,\hbox{V}^{-1}\,\hbox{s}^{-1}$$ with Sn-doping (1–2 at%). Thus, the PbS films grown by Sn-doping with improved microstructure, decreased band gap, and increased electrical properties are beneficial for IR photodetector applications.

CdS, Cd0.98Gd0.02S, and Cd0.96Gd0.04S quantum dots (QDs) have been fabricated by solvothermal method and found to form in cubic phase. Raman spectra displayed first as well as second order longitudinal modes of CdS QDs. Transmission electron microscopy images depict the nearly spheroid particles of size in the range of 3.8–6.2 nm. Reflectance spectra showed that the absorption edge of the Cd0.98Gd0.02S and Cd0.96Gd0.04S QDs was red-shifted compared to that of CdS QDs. Electron paramagnetic resonance spectra of Cd0.98Gd0.02S and Cd0.96Gd0.04S reveal resonance signals at g ≈ 2.16 and 2.93 corresponding to the gadolinium (III) ions located at sites with frail as well as intermediate crystal field. Exploration of the magnetic property reveals that the Cd0.98Gd0.02S and Cd0.96Gd0.04S QDs show signs of superparamagnetism. The photocatalytic activity of CdS and Cd0.96Gd0.04S QDs was studied on malachite green oxalate dye under artificial solar light irradiation. The decomposition rate of CdS and Cd0.96Gd0.04S QDs evaluated on the malachite green oxalate dye is as follows: Cd0.96Gd0.04S > CdS.

Pristine and Co-doped ZnS quantum dots (QDs) were fabricated via a hydrothermal technique. Morphology studies showed that the fabricated QDs were nearly spheroidal with narrow size distribution. X-ray diffraction and Raman spectroscopy analyses demonstrated that the Co ions effectively penetrated the host matrix without changing its cubic phase. A minimal blue shift was found in the pristine ZnS QDs after doping with Co. The pristine and Co-doped samples exhibited similar blue emission, while increased (two times) photoluminescence intensity was observed for the Co-doped sample. X-ray photoelectron spectroscopy analysis showed trivalent Co ions in the ZnS lattice. The diamagnetic ZnS QDs were turned into ferromagnetic through Co-doping. The Co-doped ZnS QDs portrayed higher photocatalytic degradation (PCD) of Rhodamine B dye under artificial solar simulator irradiation than pristine ZnS. Hence, the Co-doped ZnS QDs may find applications in luminescent, spintronic and photocatalytic devices.

CdS and CdS:Eu quantum dots (QDs) with relatively uniform size and a narrow size distribution were fabricated by a solvothermal method. X-ray diffraction and Raman spectroscopy analyses revealed that the synthesized samples were polycrystalline with a cubic structure. An almost spheroidal morphology with slight polydispersity was observed in both low and high-resolution transmission electron microscopy images. The optical band gap of the CdS and CdS:Eu QDs was found to be 3.1–3.3 eV. An X-ray photoelectron spectroscopy analysis disclosed the existence of Eu with a trivalent state and the obtained composition values are nearer to stoichiometry. The CdS:Eu QDs displayed room-temperature ferromagnetism. The CdS:Eu QDs showed enhanced photocatalytic activity compared to CdS during malachite green oxalate dye degradation under artificial solar illumination. Hence, Eu doping is a promising path for facilitating better photocatalytic activity and ferromagnetism of CdS.

In this study, $$\text {Cu}_{2}\text {ZnSnS}_{4}$$ (CZTS) thin films were grown on Mo-coated glass substrates by thermal evaporation of the precursor layers followed by annealing in a graphite box. The effect of annealing on the grain growth and morphology of the CZTS thin films was investigated at two different temperatures and $$\text {S}_{2}$$ partial pressures. X-ray diffraction and Raman spectroscopy analyses confirmed the formation of CZTS films with a kesterite structure with (112) preferred orientation. The grain growth was significantly enhanced by annealing the stacks at $$550\,^\circ {\text{C}}$$ for 30 min at a $$\text {S}_{2}$$ partial pressure of $$1.2 \times 10^{4}\,\text{Pa}$$ . The grain size was found to be in the range of $$1.0{-}2.0\,\upmu \text {m}$$ . The same grain size was obtained by carrying out the annealing at $$580\,^\circ {\text{C}}$$ and a $$\text {S}_{2}$$ partial pressure of $$1.96 \times 10^{4}\,\text{Pa}$$ just for 10 min. This grain size was much larger than the grain size of CZTS films obtained from annealing the stacks in two-zone tubular furnaces.

Zinc Sulfide (ZnS) quantum dots (QDs) with enhanced fluorescence efficiency and photocatalytic activity have been attained through Ga doping for the first time. Ga-doped ZnS QDs were synthesized via a solvothermal method using Polyethylene glycol (PEG) as a stabilizer. Transmission electron microscopy studies disclosed that the obtained QDs were slightly polydispersed with an average size of 5.5–3.8 nm. The results of X-ray diffraction and Raman and X-ray photoelectron spectroscopy stipulated that the Ga ions were successfully incorporated into the ZnS crystal lattice without amending their internal structure. A blue shift was noticed in the ZnS QDs when doped with Ga. The photoluminescence spectra of all the QDs displayed the same blue emission and enhanced fluorescence efficiency with increase in Ga doping content. The photocatalytic degradation of the phenol red dye under UV-light illumination was enhanced with increasing Ga doping concentration. Thus, the Ga-doped ZnS QDs are potential and favorable candidates for both photoluminescent and photocatalytic device applications.

SnS is a promising material for use in thin-film solar cells because of its suitable optoelectronic properties. So far, SnS thin films with a cubic crystal structure, prepared by chemical bath deposition, with long deposition times and low film thicknesses have been reported. Herein, we report the rapid fabrication of cubic SnS films by increasing the concentration of ammonia(aq) in the solution. SnS films deposited with low ammonia(aq) (0.1875 M) took 6 h to form 400 nm film, and the films were mixedphase. Increasing the concentration from 0.375 to 0.5625 M increased the film thickness from 600 to 1000 nm, with a deposition time of 6 h, and the formation of single-phase SnS. Further increase in the concentration from 0.75 to 0.9375 M decreased the deposition time to 4 h and increased the film thickness (1100–1300 nm). Again, increasing the concentration further to 1.125 M decreased the deposition time to 2 h and film thickness to 900 nm. Thus, increasing the concentration of ammonia(aq) increases the thickness of cubic SnS formed and decreases the deposition time. This work proposes a very useful technique for producing good-quality cubic SnS thin films in a short deposition time of 2–4 h.

In this study, we attempted to synthesize ZnO nanoparticles with various Eu3+ doping concentrations by a simple coprecipitation method for multifunctional applications. Morphology studies of the synthesized samples revealed the presence of hexagonal-shaped and monodispersed particles. A slight shift in the X-ray diffraction patterns of the Eu3+-doped ZnO samples confirmed the successful incorporation of the dopant ions into the host crystal. A change in the E2 (high)-mode intensity was ample evidence of intrinsic defects associated with the oxygen atoms. Diffuse reflectance spectroscopy studies provided sufficient evidence of tuning of the bandgap of ZnO by Eu3+ doping, with a typical red shift. X-ray photoelectron spectroscopy studies revealed the presence of Eu with a +3 state in the ZnO lattice. All the doped ZnO nanoparticles exhibited typical room-temperature ferromagnetism (RTFM). The Eu3+-doped samples displayed a higher photocatalytic degradation (PCD) of RhB dye under UV light illumination compared with the undoped ZnO nanoparticles. Thus, Eu3+ doping is an effective approach for enhancing the RTFM and PCD properties of ZnO for spintronic and photocatalytic applications.

In the present investigation, we made an endeavor to fabricate the ZnO nanoparticles and achieved the tunable properties with Nd doping. The Nd-doped ZnO nanoparticles were characterized via X-ray diffraction (XRD), Raman, and X-ray photoelectron spectroscopy (XPS) studies that confirmed the successful doping of Nd ions in the ZnO crystal lattice without amending its hexagonal phase. The particle morphology revealed nearly spherical particles with uniform size distribution. The band gap of these samples was determined using diffuse-reflectance spectra (DRS) and was found to vary from 3.17 to 3.21 eV with increasing Nd concentration. A broad and intense emission band at 1083 nm for Nd doped ZnO nanoparticles is observed and is assigned to corresponding emission transition 4F3/2 → 4I11/2 of Nd3+ ions. Furthermore, the magnetic studies indicate that the Nd doping altered the magnetic behavior of nanocrystalline ZnO particles from diamagnetic to ferromagnetic at 300 K and that the magnetization of these samples decreased with increasing Nd concentration. The tunable optical band gap as well as room-temperature ferromagnetism of these samples may find applications in both optoelectronics and spintronics.

Herein, the growth of large-grained and compact Sb2S3 thin films with good electrical properties by Sn doping using a chemical bath deposition (CBD) and annealing approach is detailed. Sn-doped Sb2S3 thin films were prepared using the CBD method with SbCl3, SnCl2.2H2O, and Na2S2O3 as source materials, and ethylenediamine tetraacetic acid (EDTA) as the complexing agent at 40 ° C for 3 h followed by annealing at 250 °C for 30 min under Ar ambience. Un-doped Sb2S3 films exhibited an orthorhombic crystal structure with lattice parameters of a= 1.142 nm, b= 0.381 nm, and c= 1.124 nm, crystalline grain sizes of 100 nm, a direct optical band gap of 1.70 eV, p-type electrical conductivity with high electrical resistivity, and low hole mobility. With Sn doping, a significant increase in the grain size of the films from 6 to > 10 μ m was observed with increasing Sn content from 1.0 to 5.5 at% followed by a decrease in the grain size. The direct optical band gap of the films was 1.71–1.72 eV. By varying Sn at%, the electrical resistivity of the films decreased, and hole mobility increased from 117 to 205 cm2 V−1 s−1 up to 5.5 at% and decreased to 166 cm2 V−1 s−1 at 7.2 at%. With the addition of 1.0–5.5 at% Sn in the Sb2S3 films, the grain growth and electrical properties of the films were drastically enhanced, which is beneficial for the fabrication of planar heterojunction solar cells.

In recent years, CuSbS2 has attracted significant research interest because of its direct optical band gap of 1.5 eV, high optical absorption coefficient, p-type electrical conductivity, and composition involving earth-abundant and non-toxic precursor elements. We prepared CuSbS2 thin films by annealing chemically grown Sb2S3 and sputter deposited Cu (Sb2S3/Cu) stacks in a graphite box, and studied the effect of the Cu/Sb ratio on the growth and properties of these films by varying the thickness of Cu while keeping the thickness of Sb2S3 constant. The Cu/Sb ratio significantly impacted the phase purity, grain growth, and morphology of the CuSbS2 films. The CuSbS2 films prepared with a Cu/Sb ratio of 0.78 showed some unreacted Sb2S3 and nonuniform grain growth. Upon increasing the Cu/Sb ratio from 0.85 to 0.97, the Sb2S3 phase was consumed completely, and phase-pure CuSbS2 with homogeneous grain formation was obtained. These films exhibited an orthorhombic crystal structure with the (410) preferred orientation. Further increase in the Cu/Sb ratio from 1.28 to 1.52 resulted in a change in the growth direction along the (200) plane and the formation of several micron-sized grains with a compact morphology and Cu3SbS4 secondary phase. The direct optical band gap of the films decreased from 1.52 to 1.48 eV when Cu/Sb ratio was increased from 0.91 to 1.28. The films exhibited p-type electrical conductivity and their electrical resistivity decreased with increasing Cu/Sb ratio. From this investigation it was clear that deviation in the Cu/Sb ratio from the stoichiometric proportion leads to inhomogeneous grain growth of CuSbS2 films, which affect the performance of devices using these films.

In this paper, we report the fabrication of Cu4SnS4 thin films by annealing chemically deposited SnS–CuS precursors at 823 K for 90 min, and we studied the effect of the (N2 + S2) pressure during annealing on the growth and properties of the Cu4SnS4 films. Films prepared at a (N2 + S2) pressure of 1.3 kPa exhibited an orthorhombic crystal structure with lattice parameters of a = 1.371 nm, b = 0.766 nm, and c = 0.643 nm, a grain size of 3–6 μm, a direct optical band gap of 1.0 eV, p-type electrical conductivity, and a hole mobility of 69.5 cm2 V−1 s−1. Increasing the (N2 + S2) pressure from 1.3 kPa to 66.7 kPa increased the grain size to more than 6 μm and the hole mobility to 150 cm2 V−1 s−1 at 26.7 kPa and then decreased to 86 cm2 V−1 s−1 at 66.7 kPa. Further increasing the (N2 + S2) pressure to 101.3 kPa resulted in the formation of a monoclinic Cu2SnS3 secondary phase. This study reveals that an annealing temperature of 823 K and a (N2 + S2) pressure of 1.3–66.7 kPa are the optimized conditions to obtain large-grained Cu4SnS4 films free of secondary phases with good optical and electrical properties.

Terbium (0, 2, and 4 at%)-doped ZnS quantum dots (QDs) were synthesized via a solvothermal method. The crystal structures of the synthesized QDs were determined to be zinc blend by X-ray powder diffraction (XRD) and Raman analyses. Transmission electron microscopy (TEM) studies revealed that particles with a mean size of 2–4 nm were formed. An X-ray photo electron spectroscopy (XPS) examination disclosed the existence of terbium with a trivalent state in the ZnS host lattice. The absorption bands of all QDs were located around 325 nm (3.81 eV) and were higher than that of the bulk ZnS band gap (3.67 eV), consistent with the quantum confinement effect. The photoluminescence spectra of the terbium-doped samples displayed five emission peaks at 467 nm (5D4→7F3), 491 nm (5D4 → 7F6), 460 nm (5D4 – 7F5), 484 nm (5D4 – 7F4), and 530 nm (5D4 – 7F3), respectively. The terbium-doped QDs exhibited a higher photocatalytic activity during the degradation of crystal violet dye under UV-light illumination compared to the undoped ZnS QDs. These interesting properties of terbium-doped ZnS QDs are potentially useful for both luminescent and photocatalysis applications.

A two-step chemical bath deposition (CBD) method that involves the deposition of films at two different bath temperatures is developed to enhance the grain growth and hole mobility of lead sulfide (PbS) thin films. The films deposited at three different conditions; first at 60 °C for 2 h, second at 30 °C for 1 h and at 60 °C for the subsequent 1 h, and finally at 60 °C for 1 h and at 30 °C for the subsequent hour. The deposition of PbS at only 60 °C for 2 h leads to the formation of cubic crystals with different sizes and hole mobility of 43.8 cm2V−1s−1. The deposition at a low temperature of 30 °C for the initial 1 h followed by the deposition at a high temperature of 60 °C for the subsequent hour increases the grain size and hole mobility to 62.2 cm2V−1s−1. However, the deposition of PbS at a high temperature of 60 °C for 1 h followed by the deposition at a low temperature of 30 °C for the subsequent hour decreases the grain size and hole mobility to 32.1 cm2V−1s−1. The PbS film deposited at low temperature in the first step acts as a seed layer for the growth of large-grained PbS in the second step. Thus, the two-step CBD method enhances the grain growth and hole mobility of PbS films. Hence, the two-step CBD method is very much useful for the growth of PbS for its applications in optoelectronic devices.

Lead sulphide (PbS), is an excellent material for optoelectronic devices owing to its tunable optical and electrical properties. PbS is largely synthesized by chemical bath deposition (CBD) method using different complexing agents. We have grown PbS thin films by CBD method using ethylenediamine tetraacetic acid (EDTA) as the complexing agent. The effects of EDTA concentration and the bath temperature were chosen for the investigation to fabricate highly crystalline PbS films. The concentration of EDTA has been varied from 0 to 40 mM and kept the other precursors as constant in the solution. The addition of 10 mM EDTA to the solution has increased the PbS film thickness to 1 . 3 μ m . EDTA has promoted the growth of (200) oriented PbS cubic crystals with decreased hole mobilities due to the reduced grain sizes. Its direct optical band gap energy decreases from 0.42 to 0.41 eV on increasing the EDTA concentration. The PbS films deposited at different bath temperatures (40–60 °C) at an optimized EDTA concentration of 10 mM showed an enhancement in the crystallinity and modified the PbS growth direction to (111) plane. The grain size predominantly increased and the shape of the grains has turned into perfect cubic crystals aligned semi-vertical to the substrate. The electrical resistivity of the films decreased from 0.79 to 0.25 Ω cm, and the hole mobilities improved from 18.3 to 46.6 cm2 V−1 s−1 on increasing the bath temperature from 30 to 60 °C. In contrast with other complexing agents, EDTA has shown favourable conditions for the growth of large-grained PbS thin films with improved hole mobilities, which is beneficial for its use in IR photodetectors.

The tunable room-temperature ferromagnetism (RTFM) of ZnO nanoparticles through Dy doping were fabricated through a simple co-precipitation method for spintronic device applications. The synthesized samples were analyzed by studying their structural, morphological, optical, chemical, and magnetic properties. X-ray diffraction, selected area electron diffraction, and X-ray photoelectron spectroscopy results display that the Dy3+ have successfully entered for a few of the Zn2+ as a substitute in the ZnO crystal lattice without altering their hexagonal structure. Morphology studies of the suspensions consist of monodisperse and slightly hexagonal shaped nanoparticles. The tunable optical band gap was observed in the ZnO samples via Dy doping, confirmed by diffuse reflectance spectroscopy studies. Declaration of RTFM of the ZnO:Dy has been established with the noticed hysteresis in M–H loops and these studies indicate that the saturation magnetization of the ZnO sample as a function of Dy content. Amalgamating with the above results, it is suggested that, the observed RTFM in the ZnO:Dy nanoparticles may be interpreted by the contribution of the magnetic moments from the unpaired 4f electrons of Dy3+ ions.

Famatinite (Cu 3 SbS 4 ) thin films were prepared by annealing chemically grown Sb 2 S 3 –CuS stacks in a graphite box at 370–430 °C for 30 min under sulfur and N 2 atmospheres. The films grown at 370 °C contain a minor CuSbS 2 phase with dominant Cu 3 SbS 4 . Those films prepared at 400 °C and 430 °C are single-phase Cu 3 SbS 4 with a tetragonal structure and lattice parameters a = 0.537 nm and b = 1.087 nm and a crystallite size of 25 nm. The grain size of the films increases as the annealing temperature is increased to 400 °C and subsequently decreases. The film morphology is compact and void-free with a grain size of 300–800 nm at 400 °C. The band gap of the films is 0.89 eV. The films exhibited p-type electrical conductivity and a relatively high hole mobility of 14.70 cm 2 V −1 s −1 at 400 °C. Their attractive optoelectronic properties suggest that these films are suitable as solar cell absorber layers.

Monoclinic $$\text {Cu}_{2}\text {SnS}_{3}$$ (CTS) thin films are prepared by annealing chemically deposited SnS–CuS precursors at 520-580 $$^{\circ }\text {C}$$ in a graphite box under atmospheric ( $$\text {N}_{2}+\text {S}_{2}$$ ) pressure, and the effects of annealing temperature and time on the grain growth and morphology of the films are investigated. The films prepared at 520 and 550 $$^{\circ }{\text{C }}$$ show improvement in grain size and the formation of uniform and compact grains with increasing annealing time. The films prepared at 580 $$^{\circ }\text {C}$$ exhibit good grain growth with grain sizes $$\sim 1.0{-}3.0\,\upmu \text {m}$$ ; however, the grain size does not increase with annealing time. Further, annealing time of 120 min at 550 and 580 $$^{\circ }\text {C}$$ leads to material loss. A small amount of $$\text {Cu}_{4}\text {SnS}_{4}$$ is detected in the films. In addition, annealing the films at 550 and 580 $$^{\circ }\text {C}$$ for 90 min with decreased CuS thickness results in a reduction of $$\text {Cu}_{4}\text {SnS}_{4}$$ phase, homogeneous grain growth with grain sizes of $$2.0{-}3.5\,\upmu \text {m}$$ throughout the film thickness, and hole mobilities in the range of $$6.0{-}5.3\,\text {cm}^{2}\,\text {V}^{-1}\,\text {s}^{-1}$$ . These results demonstrate the effectiveness of this annealing approach for producing high quality CTS films with micron-sized grains, which is useful for improving the efficiency of CTS-based thin film solar cells.

$$\hbox {Cu}_{2}\hbox {ZnSnS}_{4}$$ (CZTS) thin films were prepared by co-evaporation of Cu, ZnS, Sn and S and subsequent annealing. The effect of annealing temperature and duration on the growth of CZTS films were investigated. Thickness of these films was ~ 1.0 µm. X-ray diffraction (XRD) and Raman spectra analyses were used for phase identification. XRD analysis indicated the presence of minor CuS, $$\hbox {Cu}_{1.9375}$$ S, SnS phases in case of as-deposited films, emergence of strong CZTS phase with minor $$\hbox {SnS}_{2}$$ phase in films annealed at 550 $$^{\circ }\hbox {C}$$ for 10 min, and only formation of kesterite CZTS phase with (112) preferred orientation in films annealed at 550 $$^{\circ }\hbox {C}$$ for 30 min and 60 min as well as in films annealed at 580 $$^{\circ }\hbox {C}$$ for all durations. Energy dispersive spectroscopic analysis revealed that the films are Cu-poor CZTS in all these cases. Raman spectroscopy analysis, used to identify structurally coherent phases, $$\hbox {Cu}_{2}\hbox {SnS}_{3}$$ and ZnS, confirmed the absence of $$\hbox {Cu}_{2}\hbox {SnS}_{3}$$ phase in films annealed at 550 $$^{\circ }\hbox {C}$$ for 30, 60 min and in films annealed at 580 $$^{\circ }\hbox {C}$$ for all durations. Scanning electron microscopic studies showed improvement in particulate size from $$\sim 100-$$ 400 to 200−800 nm with increase in annealing duration at 550 $$^{\circ }\hbox {C}$$ , while such an improvement in particulate size is only observed up to 30 min at 580 $$^{\circ }\hbox {C}$$ . The direct band gap of CZTS films, determined from optical absorption studies, varied from 1.40 to 1.48 eV, based on annealing conditions. The electrical conductivity of these films was found to vary from 0.05 to 0.2 $${\Omega ^{ - 1}}{\text{c}}{{\text{m}}^{ - 1}}$$ .

We report the growth of SnS 2 thin films by annealing chemically deposited cubic SnS films under a sulfur atmosphere in a graphite box. The chemically deposited SnS films were annealed in the temperature range of 200–550 °C to understand its influence on the conversion of SnS into SnS 2 . In the X-ray diffraction analysis, the as-deposited SnS films annealed in the temperature range of 200–250 °C showed the formation of a minor SnS 2 phase along with the dominant SnS phase. The films annealed at 300 °C contained mixed phases of SnS and SnS 2 . Increasing the annealing temperature from 350 to 500 °C led to the formation of only the dominant SnS 2 phase. Further increasing the annealing temperature to 550 °C gave rise to the formation of a highly oriented SnS 2 film with hexagonal structure having (001) as the preferred orientation. The crystallite size of the SnS 2 films was found to increase from 17 nm to 25 nm with increasing annealing temperature from 350 °C to 550 °C. The lattice parameters were found to be a = 0.365 nm and c = 0.592 nm. Raman spectroscopy analysis confirmed the formation of single phase SnS 2 films at annealing temperatures above 350 °C. The morphological studies showed the conversion of the round shaped grains into flake-like ones on annealing at temperatures above 350 °C. These flakes increased in size on increasing the annealing temperature from 350 °C to 500 °C. The direct optical band gap of these SnS 2 films was found to be 2.58 eV.

High-quality Cu4SnS4 thin films are prepared by annealing chemical bath-deposited SnS–CuS stacks in a graphite box. The effects of annealing temperature on the grain growth and morphology of these films are investigated in this study. Results showed that the films prepared at 500–580 °C yielded an orthorhombic crystal structure with lattice parameters a = 1.371 nm, b = 0.766 nm and c = 0.643 nm, a crystallite size of 260 nm, an increased grain size from 2 μm to greater than 6 μm, a direct optical band gap of 1.0 eV, and p-type electrical conductivity. The films prepared at 550 °C and 580 °C exhibited a relatively high hole mobility of 150 cm2V−1s−1. These properties suggest that the films developed in this study can yield reasonable device efficiency when used as solar cell absorber layers.

Undoped, Gd doped, and (Gd, Mn) co-doped ZnO nanoparticles were fabricated via a hydrothermal method and their structural, morphological, optical, and magnetic properties were examined. X-ray diffraction and Raman spectroscopy studies confirmed that the Gd and Mn ions successfully entered the ZnO hexagonal lattice as substitute ions without changing the internal structure of the lattice. Morphology studies revealed that the synthesized nanoparticles were monodisperse and closely hexagonal shaped. The reflectance spectra showed a red shift of the absorption edge in both doped and co-doped samples. The diamagnetic ZnO sample was altered into a ferromagnetic material when doped with Gd ions, but this behavior was suppressed when Mn ions were co-doped into the matrix.

Thin films of $$\hbox {Cu}_{2}\hbox {ZnSnS}_{4}$$ (CZTS), a promising solar cell absorber, were grown by thermal evaporation of ZnS, Sn and Cu precursors and subsequent annealing in sulphur atmosphere. Two aspects are chosen for investigation: (i) the effect of substrate temperature ( $$T_{\mathrm{S}})$$ used for the deposition of precursors and (ii) ( $$\hbox {N}_{2}{+}\hbox {S}_{2})$$ pressure during annealing, to study their impact on the growth of CZTS films. X-ray diffraction analysis of these films revealed the structure to be kesterite with (112) preferred orientation. Crystallite size is found to slightly increase with increase in $$T_{\mathrm{S}}$$ as well as pressure during annealing. From optical absorption studies, the direct optical band gap of CZTS films is found to be $${\sim }$$ 1.45 eV. Room temperature electrical resistivity of the films obtained on annealing the stacks at 10 and 100 mbar pressures is found to be in the ranges 25–55 and 5–25 $$\Omega $$ cm, respectively, depending on $$T_{\mathrm{S}}$$ . Films prepared by annealing the stack deposited at 300 $${^{\circ }}$$ C under 100 mbar pressure for 90 min are slightly Cu-poor and Zn-rich with compact grain morphology.

Dilute magnetic semiconductors with extended ferromagnetic properties are heavily sought for use in next-generation spintronic devices. In this work, we show that co-doping 3 at% Al into Zn 0.44 Gd 0.03 O 0.50 nanoparticles can change their magnetic nature from weak to well-defined ferromagnetism (FM) at room temperature. X-ray diffraction (XRD), selected area electron diffraction (SAED), and Raman spectroscopy show that the Gd and Al atoms replaced the Zn atoms in the ZnO crystal lattice without forming other impurity phases. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analyses of the suspensions revealed the high crystallinity and monodispersity of the 34–44 nm nanoparticles. The undoped and Gd-doped ZnO samples showed diamagnetism and weak FM, while the (Gd, Al) co-doped samples exhibited robust room temperature FM. The enhanced FM of the Zn 0.44 Gd 0.03 Al 0.03 O 0.50 sample can be achieved by increasing the carrier concentration via Al co-doping.

Cu 3 SbS 4 is a promising material for thin film heterojunction solar cells owing to its suitable optical and electrical properties. In this paper, we report the preparation of Cu 3 SbS 4 thin films by annealing the Sb 2 S 3 /CuS stacks, produced by chemical bath deposition, in a graphite box held at different temperatures. The influence of annealing temperature on the growth and properties of these films is investigated. These films are systematically analyzed by evaluating their structural, microstructural, optical and electrical properties using suitable characterization techniques. X-ray diffraction analysis showed that these films exhibit tetragonal crystal structure with the lattice parameters a=0.537 nm and b=1.087 nm. Their crystallite size increases with increasing annealing temperature of the stacks. Raman spectroscopy analysis of these films exhibited modes at 132, 247, 273, 317, 344, 358 and 635 cm −1 due to Cu 3 SbS 4 phase. X-ray photoelectron spectroscopy analysis revealed that the films prepared by annealing the stack at 350 °C exhibit a Cu-poor and Sb-rich composition with +1, +5 and −2 oxidation states of Cu, Sb and S, respectively. Morphological studies showed an improvement in the grain size of the films on increasing the annealing temperature. The direct optical band gap of these films was in the range of 0.82–0.85 eV. Hall measurements showed that the films are p-type in nature and their electrical resistivity, hole mobility and hole concentration are in the ranges of 0.14–1.20 Ω-cm, 0.05–2.11 cm 2 V −1 s −1 and 9.4×10 20 –1.4×10 19 cm −3 , respectively. These structural, morphological, optical and electrical properties suggest that Cu 3 SbS 4 could be used as an absorber layer for bottom cell in multi-junction solar cells.

We report a detailed investigation of the effect of post-deposition annealing on the growth and physical properties of chemically grown cubic SnS films. Chemically deposited cubic SnS films were subjected to annealing in a graphite box with loaded elemental sulfur under N 2 at 150−350 °C for 10, 30, and 60 min in order to understand the grain growth and morphology of the films. Films annealed at 150−250 °C for 10 min showed improved grain size and a more uniform grain morphology. Films annealed at 150−250 °C for 30 and 60 min showed a decrease in the grain size and non-uniform grain morphology for the cubic SnS phase. Films annealed at 300 and 350 °C for 10 min revealed the formation of minor secondary phase SnS 2 , and the grain morphology changed from round shape to flake-like. Longer annealing at 300 and 350 °C improved the extent of the SnS 2 phase, and it was found to be the dominant phase after annealing at 350 °C for 60 min. The direct optical band gap of SnS films is 1.75−1.67 eV, depending on the annealing temperature and time. The films exhibited p-type electrical conductivity. The films annealed at 250 °C for 10 min showed a higher hole mobility of 77.7 cm 2 V −1 s −1 . Thus, lower annealing temperatures and shorter annealing times are favorable conditions to produce high-quality cubic SnS films.

Impurity free cobalt 3d and erbium 4f co-doped ZnS nanoparticles (NPs) were synthesized using a chemical reflux technique. The as-synthesized NPs exhibited high crystallinity and a narrow particle-size distribution. X-ray diffraction and optical analysis showed that cobalt (II) and erbium (III) ions substituted the zinc (II) ions in tetrahedral sites. The tunable bandgap for ZnS NPs was attained through mono- and co-doping. The cobalt and erbium co-doped NPs displayed a robust magnetization with an enhanced coercivity at room temperature compared with the cobalt-doped ZnS NPs; this was due to the exchange interaction between the cobalt (II) electrons as well as the localized carriers incited through the erbium (III) co-doping. The sense captured with the regulating bandgap and ferromagnetic property in a single substance opens a new platform for advanced applications in optoelectronics and spintronic devices.

Recently, thin films of cubic SnS emerges as a promising solar cell absorber layer owing to its suitable optical and electrical properties. In this paper, we report the growth of cubic SnS thin films by a chemical bath deposition technique using ethylene diamine tetra-acetic acid (EDTA) as the complexing agent. Optimization of EDTA concentration has been carried out to increase the film thickness and to obtain compact and uniform cubic SnS films with good grain size. SnS films with a thickness in the range 500− 620 nm could be obtained with increasing the EDTA concentration in the solution for a deposition time of 6 h. The X-ray diffraction analysis of these films revealed the presence of cubic SnS with (222) and (400) as the preferred orientations. The lattice parameter of these films is found to be a = 1.158 nm and their crystallite size increases from 46 nm to 60 nm with increase in the EDTA concentration from 0.075 M to 0.125 M. Raman spectroscopy analysis revealed the presence of a minor SnS 2 secondary phase in these films. X-ray photoelectron spectroscopy analysis revealed that Sn and S exhibit oxidation states of +2 and −2, respectively in these films. Scanning electron microscopic studies showed that the grain size first increased with increasing EDTA concentration from 0.075 M to 0.10 M and then decreased when the EDTA concentration is further increased to 0.125 M in the solution. The films deposited with an EDTA concentration of 0.10 M are compact and uniform with an average grain size of ∼1 μ m. The direct optical band gap of these films, estimated from their spectral transmittance (T λ ) and reflectance (R λ ) data, is found to increase from 1.67 eV to 1.73 eV with increase in the EDTA concentration from 0.075 M to 0.125 M in the solution. Hall Effect measurements showed that the films are p-type in nature. The films deposited with 0.10 M EDTA concentration exhibited higher hole mobility of 28.6 cm 2 V −1 s 1 , resistivity of 1.53 × 10 5 Ω cm and carrier concentration of 2.86 × 10 12 cm −3 . The above properties suggest that the films deposited from solution with 0.10 M EDTA concentration could be useful as solar cell absorber layer to obtain reasonable device efficiency.

Cubic SnS is a promising absorber material for thin film heterojunction solar cells. In this paper, we report the fabrication of cubic SnS films by chemical bath deposition technique. The effects of bath temperature and Na 2 S 2 O 3 concentration on the properties of the films were investigated. Films deposited at different bath temperatures showed a slightly Sn-rich composition. An increase in the bath temperature from 25 °C to 65 °C caused increase in the crystallite size from 17 nm to 70 nm. An increase in the bath temperature to up to 45 °C resulted in an improvement in the grain size, whereas a further increase in the bath temperature resulted in a slight decrease in the grain size. The band gap of the films decreased from 1.74 eV to 1.68 eV with increasing bath temperature. The films deposited from solutions on increasing the Na 2 S 2 O 3 concentration showed a slight improvement in the atomic percentage of S. The films deposited with a Na 2 S 2 O 3 concentration of 0.125 M showed a compact and uniform morphology with a grain size of ∼1 μm. With an increase in the Na 2 S 2 O 3 concentration from 0.125 M to 0.175 M in the solution, the band gap of the films increased from 1.73 eV to 1.82 eV. The films exhibited p-type electrical conductivity. The films deposited with the Na 2 S 2 O 3 concentration of 0.125 M showed a higher hole mobility of 75.1 cm 2 V −1 s −1 . Thus, the above results showed that a bath temperature of 45 °C and Na 2 S 2 O 3 concentration of 0.125 M are the optimum conditions for obtaining near-stoichiometric cubic SnS films with good structural, microstructural, optical and electrical properties.

ZnS:Tb3+ (0, 1, 3, and 5 at.%) NPs were synthesized via a hydrothermal method using polyethylene glycol as a stabilizer. The prepared samples were characterized systematically using various characterization techniques, such as energy dispersive X-ray spectroscopy, high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry .The XRD studies showed that all of the samples exhibited a cubic structure without any secondary phases. The formation of ultrafine (

$$\hbox {Cu}_{3}\hbox {SnS}_{4}$$ thin films were deposited onto soda-lime glass substrates held at $$360\,^{\circ }$$ C using spray pyrolysis technique. The influence of thiourea concentration on the growth and properties of these films is studied by varying the thiourea concentration (0.04–0.09 M) and keeping cupric chloride (0.015 M) and stannic chloride (0.005 M) concentrations as constant in solution. These films were analyzed by studying their elemental composition, structural, microstructural, optical and electrical properties using appropriate characterization techniques. X-ray diffraction and Raman spectroscopy analyses revealed that the films deposited from solutions with 0.04 and 0.05 M thiourea concentrations contain CuS and $$\hbox {Cu}_{2}\hbox {SnS}_{3}$$ (CTS) phases, respectively. Nanocrystalline $$\hbox {Cu}_{3}\hbox {SnS}_{4}$$ films with cubic structure could be obtained by increasing the thiourea concentration from 0.07 to 0.09 M in the starting solution. The lattice parameter and crystallite size of these films are found to be 0.540 and 6 nm, respectively. The direct optical band gap of these films is found to decrease from 1.75 to 1.70 eV with increasing the thiourea concentration from 0.07 to 0.09 M in the solution. The room temperature electrical resistivity of these films is found to lie in the range $$1.9\times 10^{-3}$$ – $$0.9\times 10^{-3}\Omega$$ cm.

This paper reports the structural as well as the magnetic properties of ZnS:Eu 3+ (0, 1, 2, 3, and 4 at%) nanoparticles prepared by a hydrothermal method. The compositional, structural and magnetic properties of ZnS:Eu 3+ nanoparticles were investigated by energy dispersive X-ray spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM) measurements. XRD studies confirmed that all the samples had a cubic structure with good crystallinity. TEM showed that the particles were polycrystalline with a mean size of 5–8 nm. XPS revealed the oxidation state of the Eu in the ZnS lattice to be +3. All the Eu 3+ -doped ZnS nanoparticles exhibited room temperature ferromagnetic behavior as a function of doping concentration. The observed RTFM may be interpreted by the contribution of the magnetic moments from the unpaired 4 f electrons of Eu 3+ in the ZnS:Eu 3+ nanoparticles. The interesting magnetic properties of ZnS:Eu 3+ nanoparticles may be further explored for new generation spintronic devices.

The present study describes the elemental and structural as well as the room temperature magnetic properties of pure ZnS, Zn0.96Eu0.04S, and Zn0.95Eu0.04Tb0.01S NPs. The energy dispersive X-ray spectroscopy (EDAX) perceived the existence of zinc, terbium, europium, and sulfur in the prepared samples in expected stoichiometry ratio. X-ray diffraction (XRD) studies revealed that all the prepared NPs had a cubic structure. Transmission electron microscopy (TEM) studies showed the creation of wispy particles with an average size in the range of 5–8 nm. Magnetization (M) versus applied magnetic field (H) studies indicated that the pure ZnS NPs exhibited diamagnetic behavior, whereas both Zn0.96Eu0.04S and Zn0.95Eu0.04Tb0.01S NPs evinced the ferromagnetic nature at room temperature. However, suppression in ferromagnetism was observed in Zn0.95Eu0.04Tb0.01S compared to Zn0.96Eu0.04S nanoparticles due to the interactions between the Eu–Eu ions, Tb–Tb ions, and Eu–Tb ions. The above experimental results suggesting that both doped and co-doped ZnS nanoparticles are useful for spintronic device applications.

The compositional, structural, optical and magnetic properties of ZnS , Zn 0.98 Co 0.02 S, Zn 0.98 Sm 0.02 S and Zn 0.96 Co 0.02 Sm 0.02 S nanoparticles synthesized by a hydrothermal method are presented and discussed. X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) studies revealed that all the samples exhibited cubic structure without any impurity phases. X-ray photoelectron spectroscopy (XPS) results revealed that the Co and Sm ions existed in +2 and +3 states in these samples. The photoluminescence (PL) spectra of all the samples exhibited a broad emission in the visible region. The room temperature magnetization versus applied magnetic field ( M – H ) curves demonstrated that the Sm+Co doped nanoparticles exhibited enhanced ferromagnetic behavior compare to Co and Sm individually doped ZnS nanoparticles, which is probably due to the exchange interaction between conductive electrons with local spin polarized electrons on the Co 2+ or Sm 3+ ions. This study intensifies the understanding of the novel performances of co-doped ZnS nanoparticles and also provides possibilities to fabricate future spintronic devices.

Cu 2 SnS 3 (CTS) is a promising candidate for thin film solar cells due to its suitable optical and electrical properties. In this paper, we report the growth of CTS thin films by co-evaporation of Cu, Sn and S onto soda-lime glass substrates held at 350 °C. The effect of annealing temperature on the growth and properties of these films is investigated by studying their structural, microstructural, optical and electrical properties using appropriate characterization techniques. XRD and Raman analyses revealed that the co-evaporated films contain CTS, CuS and Cu 4 SnS 4 phases. On annealing these films at 520 °C for 10 min, Cu 1.9375 S emerges as a secondary phase, CTS being dominant phase. Further increase in the annealing temperature from 550 °C−580 °C leads to the elimination of Cu 1.9375 S phase completely. The films are found to be near-stoichiometric and polycrystalline CTS with monoclinic structure having ( 1 ¯ 31)/(200) preferred orientation. The crystallite size of the annealed CTS films is found to be 70 nm. The surface morphology of the films annealed at 550 °C for 10 min is found to be compact with grain size in the range 100 nm−500 nm. The direct optical band gap of these films is found to be 0.97 eV.