ZnS Films Research Articles

ZnS Thin Films Prepared Using Spray Pyrolysis Technique

It is well known that spray pyrolysis of an aqueous solution of thiourea and zinc acetate onto a glass substrate at spray rates of (3 mlmin-1) may successfully synthesize thin coatings of zinc sulfide. The impact of several substrate temperatures (150, 200, 300, and 400 oC) on the structural and optical characteristics was also discussed in this research. Field emission scanning electron microscopy (FESEM), UV-Vis-NIR spectrometry, and X-ray diffraction (XRD) were used to characterize the films. On each one of the deposited ZnS sheets, a cubic structure was seen. On the other hand, the temperature of the substrate appeared to affect the crystallinity and morphology. It was discovered that as the substrate temperature was lowered, the bandgap value of ZnS films somewhat rose. Furthermore, it is most likely that the Zn(S,O) production inside the solid solution is responsible for the fluctuations seen in the 3.5-3.8 eV region.

Visible color camouflage and infrared, laser band stealth, compatible with dual-band radiative heat dissipation

Infrared stealth technology garners significant attention due to its value in military applications. With the rise of multi-band detection technologies, the infrared stealth target is easily detected. Therefore, it is urgent to study multi-band camouflage devices. Here, this paper proposes a multi-band camouflage device composed of ZnS, Ge, TiO2, crystalline Ge2Sb2Te5 (cGST) and Ag multilayer films, which can realize multi-band camouflage across visible, mid-wave infrared (MWIR, ε3∼5 μm = 0.22), long-wave infrared (LWIR, ε8∼14 μm = 0.16), and laser (R1.06 μm = 0.01) spectra. In addition, effective radiative heat dissipation was realized in two non-atmospheric transparent windows (ε2.5–3 μm = 0.51 and ε5∼8 μm = 0.65). Among them, visible camouflage in different background environments can be realized independently by adjusting the thickness of the ZnS film to produce different structural colors. Notably, this emissivity spectrum remains robust even as the incident angle increases to 60°. These results can guarantee the realization of multi-band infrared camouflage, laser camouflage and radiation heat dissipation. This study not only addresses high-efficiency infrared camouflage and thermal management but also achieves outstanding visible and laser camouflage performance, offering a comprehensive guidance for advancing multi-band camouflage technology.

Metamaterial structure design based on genetic algorithm and phase change material GST for multispectral camouflage

This study proposes a multispectral camouflage tunable multilayer film metamaterial (TMFM) with thermal management function based on genetic algorithm (GA), which is composed of ZnS/YbF3/Ge/Ge2Sb2Te5 (GST)/Au multilayer film. Through numerical analysis, we assess its efficacy in visible-infrared compatibility camouflage and radiative heat dissipation. Within the visible light band, different structural colors can be produced by adjusting the thickness of the ZnS film. The average emissivity within the 3–5 μm and 8–14 μm infrared bands is measured at 0.04 and 0.14, respectively. The low emissivity facilitates effective thermal management. Moreover, an average emissivity of 0.52 within the 5–8 μm range is instrumental in achieving efficient radiation heat dissipation. Laser stealth capability is further enhanced, with an emissivity reaching 0.70 at 10.6 μm. Therefore, this metamaterial structure has broad application prospects in both military and civilian industrial fields.

Design of ZnS nanospheres antireflective structure for mid and far infrared applications

Developing high-performance mid and far infrared antireflection films is a significant requirement in the field of infrared optics. This study successfully prepared AR films composed of ZnS nanospheres for mid and far infrared bands using a combination of hydrothermal and sol-gel methods. Initially, ZnS nanospheres with uniform size and good monodispersity were synthesized via the hydrothermal method and subsequently coated on CdSe substrate through dip coating. The refractive index of the ZnS film is adjusted between 1.36 and 1.52. A significant AR effect was observed in ZnS nanospheres film on CdSe substrate at 3–5 μm and 8–14 μm, and the reflectance is approximately 3 % which is about 25 % lower than that of the uncoated sample. Upon coating with a TiO2 protective layer, the reflectivity further decreased to about 0.6 % and the film demonstrated excellent weather resistance and mechanical properties. This work provides a novel approach for the preparation and regulation of mid and far infrared AR film, significantly contributing to the development of optical film.

Improvements of multifunctional spintronic and optoelectronic applications of nanostructured Eu-doped ZnS thin films through magnetic and linear, nonlinear optical investigations

This study describes the spintronic and optoelectronic improvements upon Eu substitution in Zn atomic site of the nanostructure ZnS thin films. The electron beam deposition technique has been used to deposit a series of Zn1-xEuxS thin films on a glass substrate with different Eu dopants (x = 0, 0.01, 0.03, 0.05, and 0.08). The nanostructure nature of the Eu-doped ZnS thin film has been confirmed from structural and morphology studies performed by the X-ray diffraction (XRD) and atomic force microscope (AFM) measurements. XRD investigations further show a hexagonal-type structure with no detectable extra phases with the lattice parameter c increasing, while a decrease linearly with increasing Eu-dopant in the ZnS hosted lattice. The microstructures analysis reveals a reduction in the mean crystallite size and increasing in the lattice strain of the films with rising Eu doping. The Fourier transform infrared spectra display the existence of chemical bonds in the thin films whereas photoluminescence reveals near-band edge emission. The linear optical parameters were obtained from the analysis of the transmission data measured by the spectrophotometer technique. The results reveal that the band gap energy (EgOpt) reduces by raising ohe Eu doping ratio, which is ascribed to the structural deformation (strain and/or defects) confirmed from structural analysis, density of localized states and PL measurements. The index of refraction n was calculated using the Swanepoel method. The values were found to increase as the level of Eu doping grows, which is associated with the rise in polarizability. Wemple and DiDomenico's (WDD) model was utilized to compute the dispersive and oscillator energies (Eo, and Ed), the nonlinear absorption coefficient βc, nonlinear refractive index n2, and nonlinear optical susceptibility χ3. The results demonstrate that the adjustability of EgOpt , Eo, and Ed of ZnS: Eu films is conducted to improve the nonlinear optical characteristics, providing it well-suited for optoelectronic device implementations. On the other hand, ZnS doped with Eu film displays inherent ferromagnetic properties at room temperature, as evidenced by the results of the magnetic investigation. This finding could be attributed to the presence of sulphur defects (vacancies), as supported by photoluminescence (PL) measurements, which lead to the creation of the bound magnetic polaron. These discoveries indicate the potential of utilizing Eu-doped ZnS film in the effective development of spintronic devices.

Binary ZnS–ZnO films as an alternative buffer layer for solar cell applications

In this research, binary ZnS–ZnO films were fabricated by a two-step process, offering an alternative buffer layer solution for photovoltaic solar cell applications. ZnS films were attained through thermal evaporation, after which they were annealed in air at separate temperatures resulting in films containing both ZnS and ZnO phases. Structural, electrical, ellipsometric, optical, and surface properties were examined in detail to elucidate their applicability as a buffer layer in photovoltaic applications. X-ray diffraction patterns revealed that the films exhibit cubic ZnS and hexagonal ZnO crystal structures, wherein crystallite size is augmented with higher annealing temperatures. ZnS films exhibited a needle-shaped surface morphology, as confirmed through atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) images. Annealing caused noteworthy modifications on the surfaces of the films. Additionally, absorption spectra denote two distinct absorption regions forming as a result of the annealing process, possibly indicating the emergence of ZnS and ZnO phases. Photoluminescence analyses demonstrate that binary ZnS–ZnO films exhibit greater emission intensities than single-phase ZnS films. Additionally, the annealing process caused the electrical resistivity of films to reduce from 1.28 × 105 to 3.84 × 101 Ω cm. These results suggest that binary ZnS–ZnO films produced via annealing can be considered as promising buffer layers in potential photovoltaic solar cell applications.

Effect of Ag incorporation on the microstructure and properties of ZnS thin films

In this study, ZnS thin films doped with different content of Ag were deposited on quartz glass substrates by RF magnetron sputtering technique and were annealed at 600 °C in sulfur vapor. The crystal structure, grain size, surface morphology, composition, optical properties and defects of the doped ZnS thin films were analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), UV–Vis spectroscopy and positron annihilation doppler broadening spectroscopy (DBS). The results showed that all films exhibited the cubic sphalerite structure with a preferred orientation along the (111) crystal plane, and the composition of the doped films were more consistent with the stoichiometric ratio compared to the undoped film. The grain size gradually increased as the Ag content grew, indicating the improvement of crystallinity of the ZnS thin films. Besides, the bandgap values of these ZnS films with good optical transparency in the visible region were decreased from 3.87eV to 3.53eV as the Ag content grew. DBS results also showed that the defect concentration of ZnS films gradually decreased from the surface to the inner layer, and the film defects decreased with the increase of Ag content. However, the types of defects changed when the Ag content increased. Furthermore, the results showed Ag also has an effect on the porosity of ZnS thin films.

Highly responsive and selective ozone sensor based on Ga doped ZnS-ZnO composite sprayed films.

Ozone detection is currently the subject of wide scientific and technological research, motivated by its harmful impact on human safety, environment and health. With the aim of searching for new highly sensitive materials for ozone detection, Ga-doped ZnS and ZnS-ZnO films were deposited by a spray pyrolysis technique. The obtained films were annealed at 400 °C for two hours. The ozone sensing properties were investigated by measuring the sensor resistance for several ozone concentrations ranging from 30 to 120 ppb. The sensor response reveals a dependence on the gallium concentration. The best response was obtained with 4% doping gallium. The sensitivity is 4.5 ppb-1 at 260 °C and the response to 30 ppb ozone is 150. Moreover, the sensor shows high performance such as good selectivity and fast rapidity.

DFT theoretical and experimental investigations of the effect of Cu doping within SILAR deposited ZnS

In this work, the effect of copper doping within ZnS on glass substrates was studied using integrated theory and experiments. Experimentally the pure ZnS and Cu-doped ZnS, for a variety of Cu concentrations (2 %, 4 %, 6 %), were grown, on a glass substrate, using the SILAR technique with 30 deposition cycles. Theoretically, the full potential linearized enhanced plane wave (FP-LAPW) approach based on density functional theory (DFT), using the TB-mBJ and PBE_GGA approximations, was employed to study the structural, electronic, and optical properties of copper-doped ZnS. The structural, morphological, and optical properties of deposited films were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and ultraviolet–visible-Near Infrared spectroscopy. XRD patterns demonstrate that all films were polycrystalline which corresponds to the hexagonal wurtzite with the (103), (104), and (105) directions as the preferred orientation. The crystalline particle size of the samples decreased, suggesting a change in crystallinity with Cu doping. The surface morphology showed that pure ZnS and Cu-doped ZnS present a rough, granular surface. EDX analysis confirms the expected dopant element presence in ZnS film. UV spectrophotometry experiments reveal that Cu incorporation causes a slight decrease in the optical gap energy from 3.74 to 3.67 eV, which confirms that the Cu atom reduces the band gap of this material.

Characterization of ZnS films on different substrates by pulsed laser deposition

ZnS films were deposited on Si and quartz substrates via pulsed laser deposition, and the structure, morphology and photoelectric characteristics of as-deposited and annealed ZnS films were compared. X-ray diffractometer results show that ZnS films are polycrystalline, and the intensity of peak at 28.4° on Si is larger, with a narrower FWHM. atomic force microscope topographies show that the surface of ZnS films becomes rough after annealing, and the roughness on quartz is obviously larger than that on Si. The transmittance of ZnS films in the visible light region reaches 80%, which indicates that ZnS is suitable for making transparent conductive films. PL spectra show that there are two luminescence peaks at 425 and 445 nm related to the intrinsic defect levels of ZnS. Due to the small lattice mismatch, PL intensity on Si is significantly weaker than that on quartz. I–V characteristics of ZnS/p-Si heterojunctions show typical p–n junction diode-like rectification behavior.

Effect of Lanthanum Doping on Properties of ZnS Thin Films for Water Splitting

A chemical bath deposition technique was used to create the transparent, finely adherent ZnS and Lanthanum doped ZnS thin films on a glass substrate. The films were obtained in a water bath with reaction solutions containing Zinc, Lanthanum precursors, and trisodium citrate as a complexing agent. The amorphous nature of the films was confirmed by an X-ray diffractometer and the porosity of the films was checked by field emission scanning electron microscope. The presence of Lanthanum in ZnS films was confirmed by EDS. To find the band gap UV-Visible spectroscopy analysis was carried out. The impurity phase and the Raman modes were recognized by Raman spectroscopy. Further studies on the water splitting and photocatalytic degradation of organic dyes using La-ZnS nanomaterials are underway in our laboratory.

Fabrication of n-ZnS/p-SnS, n-ZnO/p-SnS, and n-SnO2/p-SnS heterojunctions by 2-step SILAR process for photodetector applications

In this work, we present the fabrication and detailed analysis of three functional heterojunctions based on SnS. Unlike most of the previous reports, all semiconductor layers in the heterojunctions were deposited using the low-cost SILAR technique. The ZnS, ZnO, and SnO2 films, each with a thickness of 400 nm, were grown on a previously deposited 800 nm SnS layer, forming n-ZnS/p-SnS, n-ZnO/p-SnS, and n-SnO2/p-SnS heterojunctions. Current-voltage characteristics confirmed the successful formation of p-n junctions. Various models were used to estimate junction parameters such as diode ideality factor, barrier height, and series resistance. The fabricated diodes exhibited a prominent photo response under illumination. Photodetection figures of merit were estimated for all the devices. n-ZnS/p-SnS showed 0.003μA response current, with 0.27 sensitivity. The responsivity observed was around 0.6 μA /W with LDR of 2.09 dB. The specific detectivity was 106 Jones. Similarly, n-ZnO/p-SnS showed 0.021μA response current, with 0.38 sensitivity. The responsivity observed was around 4.2 μA /W with LDR of 2.80 dB. The specific detectivity was 106 Jones. However, n-SnO2/p-SnS showed remarkable figures of merit such as 2.4 μA response current, with 8.40 sensitivity. The responsivity observed was around 488 μA/W with LDR of 19.47 dB. The specific detectivity was 109 Jones. The rise and decay time of the photocurrent were 5 and 7 s, respectively.

Influence of molar concentration on structural, morphological, optical and luminescence of polyvinyl alcohol-capped nanostructured ZnS films

Nanostructured ZnS films of various molar concentrations have been deposited using chemical bath deposition (CBD) method on glass substrates in the matrix of polyvinyl alcohol (PVA). Structural analysis of the samples with the help of X-ray diffraction (XRD) shows that the films are of cubic phase structure and diffraction peaks shift toward higher diffraction angle with the increase of molar concentration. Crystallite size is obtained using Scherrer’s formula, Williamson–Hall (WH) plot as well as size–strain plot (SSP), and reveals decrease in size with increasing molar concentration. Surface morphology and surface texture of the samples are observed with the help of atomic force microscopy (AFM) and high-resolution transmission electron microcopy (HRTEM) which exhibit the roughly spherical shape of the particles as well as formation of cluster by a large number of ZnS nanoparticles. Observation from selected area electron diffraction (SAED) pattern also confirms the cubic phase of nanostructured ZnS samples. Surface topographic study using scanning electron microscopy (SEM) also shows particle agglomeration forming nanoclusters and energy-dispersive X-ray spectroscopy observation reveals that the films are composed of zinc and sulfur. With the increase of molar concentration, the optical bandgap energy increases whereas the refractive index as well as dielectric constant decrease, and in comparison to ZnS bulk counterpart, the samples are found to be blue-shifted. Samples exhibit blue emission photoluminescence (PL) band and second-order Raman scattering. Fourier-transform infrared (FTIR) technique is utilized to detect the presence of stabilizing agent.

Effect of copper and silver as a middle layer on the structural, electrical, photocatalytic, and optical properties of ZnS/metal/ZnS films for optoelectronics applications

In this work, we utilized the thermal vacuum evaporation technique to fabricate ZnS single-layer thin films, ZnS/Cu/ZnS (ZCZ), and ZnS/Ag/ZnS (ZAZ) multilayer thin films. The influence of the middle layer of metals like copper and silver on the physical properties of ZnS/metal/ZnS multilayers is investigated. The results of the X-ray investigation demonstrate that the samples are polycrystalline, with a cubic ZnS structure and texture (111) at 2 = 29.1°. The optical investigation using Tauc’s approach yields energy gap values of 3.76 eV, 3.68 eV, and 3.6 eV for ZnS, ZCZ, and ZAZ films, respectively. CO2 gas sensing efficiency of ZnS, ZCZ, and ZAZ films were found to be at different operating temperatures. The optimal temperatures for ZnS, ZCZ, and ZAZ thin films were determined to be 483 K, 693 K, and 693 K, respectively. Under ultraviolet (UV) irradiation, the photocatalytic activity of ZnS, ZCZ, and ZAZ films for the degradation of methylene blue were studied. The results suggest that the metal intermediate layer is significant in improving the photocatalytic capabilities of ZnS films. When compared to ZnS single layer film (degradation efficiency of 15% after 180 min of UV irradiation), ZAZ multilayer film demonstrates the highest photocatalytic activity (degradation efficiency of 50% after 180 min of UV irradiation). The mechanism of the metal middle layer’s improved UV photoactivity is briefly discussed.

Fabrication and optical-electrical characteristics of ZnS/ZnO films by pulsed laser deposition

Zinc sulfide/Zinc oxide (ZnS/ZnO) films were prepared on silicon (Si) wafers at different temperatures via pulsed laser deposition, and the structure, morphology and optical characteristics were investigated. As the growth temperature increases, the crystallization quality of ZnS and ZnO films improves, and the surface morphology of ZnS/ZnO films becomes more uniform and dense, accompanied by grain growth. Photoluminescence spectra of ZnS/ZnO films show that there are two emission peaks located at about 380 and 500 nm. With the increase of growth temperature, the luminescence intensity of the two peaks increases first and then decreases, and the reduction of ultraviolet luminescence is more obvious, accompanied by the blueshift of the peak position. ZnS films have played a major role in the green luminescence of ZnS/ZnO films. The average transmittance of ZnS/ZnO films is about 75% in the visible light region. With the increase of growth temperature, the transmittance increases gradually, accompanied by the absorption edge moving towards the short wavelength. Current-voltage characteristics of ZnS/ZnO/Si heterojunctions show similar rectifying behavior with common p-n junction diodes. This indicates that ZnS/ZnO films have potential applications in optoelectronic devices.

Effect of the tri-sodium citrate as a complexing agent in the deposition of ZnS by SILAR

Using the SILAR method Zinc sulfide coatings were deposited on glass slices. The physical properties and the chemical mechanism throughout the variation in concentration of tri-sodium citrate (TSC) as a chelating agent in the synthesis of thin films were investigated. Results shows that ZnS thin films exhibit an average transmittance of 16% in visible light spectra region and a zinc blende structure. The ZnS films synthesized using TSC as a complexing agent, present a smaller average particle size, an average transmittance of 85%, and an adsorption edge at 300–340 nm. Based on our experimental data and analysis, we conclude that the contribution of the oxychloride species, a subproduct in the chemical deposition, is suggested to be related as an impurity level former in the synthesis of ZnS thin films. TSC as a complexing agent in the SILAR technique is a non-toxic option to reduce the generation of the oxychloride species and synthesize a wide band gap semiconductor. Moreover, the use of complexing agents could be extended to other types of semiconductors deposited by SILAR.

Formation and characterization of ZnS and CdZnS films using open-air chemical vapor deposition for buffer layers of compound semiconductor solar cells

ZnS and CdZnS (a mixed crystal phase of ZnS and CdS) were formed using the open-air CVD method. Cadmium diethyldithiocarbamate (C10H20CdN2S4) and zinc diethyldithiocarbamate (C10H20ZnN2S4) were used as the source materials for CdS and ZnS, respectively. By changing the ratio of source materials, it was found that the bandgap and the lattice constant of the CdZnS film were continuously changing without a miscibility gap. Furthermore, the bandgap of the obtained ZnS films was less than the reported bandgap of ZnS (3.68 eV) due to incorporation of oxygen. X-ray diffraction analysis revealed that the increase of Zn in CdZnS film generated a crystalline disorder. When the substrate temperature was changed from 421 °C to 464 °C, the deposition rate increased fourfold for the CdS and ZnS films. The impact of substrate temperature on the bandgap and lattice constant was found to be less pronounced.

Electrically erasable writing properties of ZnS films by conductive atomic force microscopy

Resistive switching cycles were realized in Au/ZnS/substrate (indium–tin oxide (ITO), Cu, Si) structures, and electrically erasable writing operations were achieved in the Au/ZnS/Si structure using conductive atomic force microcopy. High-resolution transmission electron microscopy revealed that high resistance state was a mixture of amorphous and nanocrystalline state, while the frequency response of alternating current conductivity indicated that the low resistance state (LRS) was only nanocrystalline. Electric field and thermal effects contributed to the distribution of conductive defects in the ZnS film, and nearest-neighbor hopping conduction controlled the electrical resistance of the Au/ZnS/ITO structure. X-ray photoemission spectroscopy analysis of conductive defects of ZnS films in the LRS revealed that they were zinc-rich or sulfur-poor. This study confirms the intrinsic resistive switching characteristic of ZnS films, which can serve as nonoxide materials for nonvolatile memory application.

Analysis of surface properties of Mg doped ZnS and ZnSe thin films through x-ray photoelectron spectroscopy

The surface properties of the spray-deposited Mg-doped ZnS and ZnSe films were investigated using X-ray photoelectron spectroscopy (XPS). The energy levels of the core electrons in ZnMgS and ZnMgSe, their peak positions, area ratios, and full width at half maximum were determined. Chemical shifts in Auger peaks, which are highly sensitive to changes in the chemical environment were used in the analysis. Compositional analysis indicated selenium deficiency in the ZnMgSe films. XPS peak of magnesium 2p showed a shift from 50.46 eV for ZnMgSe film to 50.63 eV for ZnMgS film and Mg 2s peak shift from 86.56 eV for ZnMgSe to 87.64 eV for ZnMgS films. A careful justification for the formation of oxides in the ZnMgSe films is also given. Ionicity for both films is about 0.51. Peak shifts in the Auger and core-level peaks are used to analyze the material's bonding strength, oxidation states, and bonding types.

Linear and third-order nonlinear optical properties of spray pyrolysis deposited Mn doped ZnS nanostructured thin films for optoelectronic device applications

The undoped and 10 wt% of Mn-doped ZnS thin films have been deposited on a glass substrate at 350 °C using the spray pyrolysis technique. The structural, morphological, linear and third-order nonlinear (NLO) properties are reported. The XRD pattern showed that ZnS thin film has a cubic structure. The FESEM images show the uniformity of coating and improvement in the smoothness of the surface after adding the Mn dopant to the ZnS lattice. Using a UV–VIS spectrophotometer the optical energy band gap of ZnS film was found to be 3.71 eV and for 10 wt% of Mn-ZnS is 3.76 eV. By the method of Z-scan, the materials demonstrated good nonlinear absorption (NLA), nonlinear refraction (NLR) and third-order NLO susceptibilities. The magnitude of third-order NLO susceptibilities (χ)(3) 10-6 esu, NLA coefficient (β) 10-5 mW−1 and nonlinear refraction (n2) 10-8 cm2/W. The positive findings of NLO of Mn: ZnS thin film as optoelectronic devices and optical switching applications.