ZnS Films Research Articles

The choice of Zn or ZnS layer in the stacked precursors for preparation of Cu2ZnSnS4 (CZTS) thin films

Cu2ZnSnS4 (CZTS) thin films are commonly used as an absorber layer in the thin film solar cell structure. In this study, CZTS thin films were produced by sulfurization of stacked precursor films that is prepared by deposition of Cu, Zn, SnS, ZnS films on glass substrate using sputtering method. The sequential sputter deposition was performed to obtain two distinct stacked precursors, Cu/SnS/Zn/Cu and Cu/SnS/ZnS/Cu respectively. Afterwards, annealing process was implemented at various reaction temperatures (500–575 °C) for 1 min utilizing rapid thermal processing (RTP). The EDX measurements revealed that all the prepared CZTS samples had Cu-poor and Zn-rich composition that are non-stoichiometric chemical composition. This non-stoichiometric composition is important for high efficient CZTS based solar cells. XRD measurements revealed that all patterns are dominated by diffraction planes of kesterite CZTS. The CuS, Cu2S and SnS2 secondary phases also were detected in the XRD pattern of some CZTS films. Raman spectroscopy measurements verified formation of kesterite CZTS phase for all films and picked out CTS phase for some samples prepared using Cu/SnS/Zn/Cu precursor films. The surface microstructure of the films that were obtained through SEM displayed polycrystalline surface structure. Room temperature PL emission spectra of the films showed broad peak at around 1.37–1.38 eV, which is near to the optical band gap of kesterite CZTS structure. Electrical characterization of the samples demonstrated that B-525 CZTS thin film has more suitable electrical resistivity and carrier concentration values for CZTS based solar cell applications.

Activating hemimorphite using a sulfidation-flotation process with sodium sulfosalicylate as the complexing agent

In this paper, the effects of sodium sulfosalicylate on hemimorphite activation were studied. Sulfosalicylic acid ions enhanced the sulfidation-flotation process, which increased the flotation recovery by 49.70%, and after lead ion assisted activation, the flotation recovery subsequently increased by 13.11%. Time-of-flight secondary ion spectrometry (TOF-SIMS) surface analysis revealed that the surface structure of the hemimorphite was greatly damaged by sodium sulfosalicylate, which could promote ZnS film formation for obtaining hemimorphite hydrophobicity. The ZnS film thickness on the hemimorphite surface was approximately 41.78 nm with direct sulfidation. After activating sulfidation, excellent flotation effects were obtained as the ZnS film reached about 418.19 nm. 3D images showed a heterogeneous and homogeneous ZnS film on the hemimorphite surface after direct sulfidation and activating sulfidation, respectively. The X-ray photoelectron spectroscopy (XPS)-based analysis of the substances on the hemimorphite surface further indicated that the atomic concentration of sulfur on the surface of the activating sulfidation hemimorphite nearly double that of the direct sulfidation hemimorphite (1.57% versus 2.38%, respectively). After activating sulfidation, the XPS spectra indicated that a deep complexation reaction occurred with sodium sulfosalicylate on the hemimorphite surface with various elements and significantly influenced elemental distribution on the hemimorphite surface.

An In-Depth Study of Zn Metal Surface Chemistry for Advanced Aqueous Zn-Ion Batteries.

Although Zn metal has been regarded as the most promising anode for aqueous batteries, it persistently suffers from serious side reactions and dendrite growth in mild electrolyte. Spontaneous Zn corrosion and hydrogen evolution damage the shelf life and calendar life of Zn-based batteries, severely affecting their industrial applications. Herein, a robust and homogeneous ZnS interphase is built in situ on the Zn surface by a vapor-solid strategy to enhance Zn reversibility. The thickness of the ZnS film is controlled via the treatment temperature, and the performance of the protected Zn electrode is optimized. The dense ZnS artificial layer obtained at 350 °C not only suppresses Zn corrosion by forming a physical barrier on the Zn surface, but also inhibits dendrite growth via guiding the Zn plating/stripping underneath the artificial layer. Accordingly, a side reaction-free and dendrite-free Zn electrode is developed, the effectiveness of which is also convincing in a MnO2 /ZnS@Zn full-cell with 87.6% capacity retention after 2500 cycles.

Distinct and enhanced ultraviolet to visible ZnS-porous silicon (PS):p-Si hybrid metal-semiconductor-metal (MSM) photodetector

Present article reports distinct and enhanced ultraviolet to visible light sensing property of metal-semiconductor-metal (MSM) based ZnS-PS:p-Si hybrid heterostructure. PS:p-Si heterostructure is prepared using electrochemical anodization technique by alternate variation of etching current density within the limit of 17.2–22.1 mA cm−2. ZnS (99.99% purity) in powder form is deposited on PS:p-Si surface via thermal evaporation technique under a chamber pressure of 2 × 10−5 m bar. To achieve MSM configuration Au electrode of ∼8 nm and Al electrode of ∼22 nm thickness are successively coated on top of ZnS-PS:p-Si surface using a shadow mask with dimension of 6 × 6 mm. Morphological features of the heterostructure are observed and analysed using cross section FESEM. This gives thickness of the deposited ZnS layer as around ∼110 nm on ∼540 nm thick PS:p-Si structure. These also confirm uniform interface between the two i.e, ZnS and PS:p-Si layers. Cross sectional EDX analysis indicates diffusion of ZnS particles into the PS layer. Optical analysis observed via UV–Visible spectroscopy gives bandgap (obtained through Tauc plot) of the bare ZnS film to be 3.4 eV with 70–90% transparency in the visible region (390–700 nm). Optical reflectance spectrum of the prepared heterostructure shows decreased reflectivity compared to that of the bare PS:p-Si structure which is itself 20–30% less compared to bulk silicon. Spectral response measured for the wavelength range of 200–500 nm gives distinct and enhanced responsivity peak values of ∼0.94 and ∼1.12 AW−1 at 365 nm (UV) and 400 nm (visible) compared to ∼0.5 AW−1 (maximum at 400 nm) of bare PS:p-Si MSM structure for bias voltage of −4 V. The response and recovery times of the heterostructure are found to be 0.54 ± (4.3×10-4) s, 0.38±9.5×10-5 s and 0.50±2.8×10-4 s, 0.35±6.5×10-5 s under UV and visible irradiations.

Achieving desired quality of ZnS buffer layer by optimization using air annealing for solar cell applications

The possibility of maximum transmittance at lower thickness of light transmitting ZnS layer and its optimization by air-annealing as an alternative to hazardous and expensive CdS is reported in this communication in order to achieve better buffer layer for solar cells. Thin films of ZnS were deposited using e-beam evaporation on glass and ITO substrates and subjected to air-annealing followed by characterizations for physical properties. XRD patterns revealed amorphous behavior which transformed into cubic (111) plane with change of substrate and annealing whereas surface topography reveals hill and deep valley like structures. Optimal transmittance of maximum 95% in visible region, direct band gap of 3.38 eV and maximum electrical conductivity were observed for 200°C annealed films. The study refers that films annealed at 200°C are claimed to be suitable for buffer layer applications.

Effect of bath temperature on morphological and optical properties of ZnS films prepared by electrochemical deposition technique

Effect of bath temperature on morphological and optical properties of ZnS films prepared by electrochemical deposition technique

Impact of Hydrogen flow rate on physical properties of ZnS thin films: As potential buffer layer in solar cells

The exceptional need of potential Cd-free buffer layer in thin film solar cell devices motivated us to study the role of post-deposition Hydrogen annealing for the optimization of physical properties of ZnS thin films. The deposited films of thickness 200 nm were hydrogenated within the flow rate range of 50.0–150.0 sccm at 200 °C. XRD analysis revealed transformation of amorphous into cubic phase with maximum crystallinity at 150.0 sccm for films deposited on glass substrate while into wurtzite structure for films on ITO substrate with enhanced crystallinity. A mixed phase (cubic and hexagonal) at 150.0 sccm also appeared. Electrical behaviour (I–V) exhibits ohmic nature with maximum carrier concentration at 100.0 sccm. The blue shift in absorption edge and maximum of 95% transmittance were recorded in the visible region with optical energy band gap of 3.41 eV at 150.0 sccm. The reduction in surface roughness is observed in surface topographical analysis while the photoluminescence (PL) study indicated a sharp peak at 2.95 eV with strongest emission for 150.0 sccm attributed to reduction of defects at interstitial sites and passivation of grain boundaries. These results are useful to understand the Hydrogen related impurities in ZnS films and the improvement caused by hydrogenation to physical properties suited for buffer layer in solar cells.

Novel ultraviolet photodetector with ultrahigh photosensitivity employing SILAR-deposited ZnS film on MgZnO

Abstract A novel MgZnO/ZnS heterojunction-based ultraviolet (UV) photodetector (PD) with high performance is fabricated by a facile sol-gel process and a successive ionic layer adsorption and reaction (SILAR) method. ZnS is coated onto the MgZnO film as an interface modification layer, which overcomes the drawbacks of the pristine MgZnO photosensitive layer, such as lower carrier mobility and more traps in the material, and greatly enhances UV-light absorption. The type-II heterostructure constructed by work function differences near the interface facilitate the separation of photogenerated carriers. Compared with the MgZnO PD, the optimized heterojunction PD (MgZnO/ZnS-10) yields a dramatically decreased dark current (≈1 nA), a remarkable responsivity (900 A/W) and an ultrahigh photo-to-dark current ratio (up to 2.3 × 105) under 325 nm light illumination at 5 V bias. These results provide a cost-efficient means for improving the properties of MgZnO PDs, and show the advantages of MgZnO/ZnS heterojunction PDs in UV detection. This study demonstrates that rational construction of novel heterojunctions holds great potential for fabricating high-performance photodetectors.

Enhancing the solar photocatalytic hydrogen generation of ZnS films by UV radiation treatment

This work reports the synthesis of transparent ZnS films for the hydrogen production using a low-cost chemical bath deposition method (CBD). Some ZnS films were subjected to UV treatment and became darker. According to the X-ray diffraction patterns, both, the transparent and dark films presented the same crystalline wurtzite phase. However, the morphological analysis by scanning electron microscopy (SEM) revealed that the dark ZnS films were formed by smaller ZnS grains (10–46 nm) in comparison with the transparent films (17–70 nm). The dark coloration of the films was caused by the presence of Zn vacancies, S vacancies and sulfate groups as confirmed by the XPS spectra and absorbance measurements. In fact, the presence of these defects and sulfates enhanced the absorbance and photocurrent in the dark ZnS films with respect to the transparent ZnS films. Consequently, the maximum hydrogen generation rate was 250% higher in the dark ZnS films (655 μmol∙h−1 g−1) in comparison to the transparent ZnS films (187 μmol∙h−1 g−1). In presence of a sacrificial agent (Na2SO3), the hydrogen generation rates increased up to 2903.6 and 5202.4 μmol∙h−1 g−1 for the transparent ZnS and dark ZnS films, respectively. The ZnS films studied here represent advance with respect to the previous powder-type binary/ternary photocatalyst nanocomposites, since they can be easily removed from water after the photocatalytic reaction (an advantage over the powders), they do not contain expensive/rare metals and their synthesis procedure is not as complex as these reported for binary/ternary nanocomposites.

Enhanced Transmittance and Photoelectrochemical 2D Nanostructured N-Type Semiconductor ZnS Thin Film Prepared by One-Step Electrodeposition in a Non-Vacuum-Processed CIGS Cell

Two-dimensional N-type semiconductor nanostructured ZnS films for use in optical semiconductor applications were fabricated via a comparatively facile and low-cost electrodeposition method. Electrodeposition was carried out at a current density of 1.5 mA cm–2 at 60°C. ZnS was produced and deposited on the cathode, and crystalline grains developed. Subsequently, islands of discontinuous N-type semiconductor nanoparticles grew, which decreased the cathode conductivity to control the thickness of the film within the nanometer range. To characterize the structure, composition and chemical state of the nano-film, scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were employed. The results showed that the ZnS nano-film was successfully prepared, with uniform and dense surface morphology and a wurtzite structure. The 4-min electrodeposition resulted in a ZnS nano-film with thickness of 89.15 nm. The band gap of the ZnS nano-film of the N-type semiconductor was 3.75 eV.

Influence of argon pressure on the crystalline phase formation of RF sputtered zinc sulfide thin films

Zinc Sulphide thin films on quartz substrates, were deposited using RF sputtering with variable argon pressures, to assess its effect on the crystallinity and surface morphology. Structural analysis by XRD reveals the formation of crystalline ZnS films, with preferential growth along hexagonal (1 0 3) direction, at a low argon pressure of 0.02 mbar and preferential growth along cubic (1 1 1) direction, at an argon pressure greater than 0.02 mbar. It has been found that crystallinity, is improved at argon pressure of 0.1 mbar. An exponential decrease in film thickness & RMS surface roughness is observed, increasing argon pressure.

TiO2/CuS core-shell nanorod arrays with aging-induced photoelectric conversion enhancement effect

Highly ordered three-dimensional (3D) heterojunctions are attractive for optoelectronic, photovoltaic and electronic devices due to their large interfacial contact and oriented charge transport. However, 3D heterojunctions of this type have rarely been reported because of the great difficulty in constructing an ordered structure at the nanoscale. In this study, a core-shell nanorod array of TiO2/CuS heterostructure is achieved by coating the TiO2 nanorods with conformal ZnS films and subsequently converting the ZnS into its CuS counterpart via ion exchange. The TiO2/CuS-based photovoltaic devices exhibit a gradually enhanced efficiency when aging in air up to 22 days. This is attributed to the progressive conversion from Cu deficient sulfide to CuS. This strategy could also be used to design other core-shell nanorod arrays based on metal oxide/sulfide heterojunctions.

Comparison of ZnS Film Growth on Glass and CIGS Substrates via Hydrazine-assisted Chemical Bath Deposition for Solar Cell Application

Comparison of ZnS Film Growth on Glass and CIGS Substrates via Hydrazine-assisted Chemical Bath Deposition for Solar Cell Application

Influence of Cd on structure, surface morphology, optical and electrical properties of nano crystalline ZnS films

Transparent nano crystalline Zn1-xCdxS films were grown on glass substrates at 0.0125 M precursor concentration using chemical spray pyrolysis technique. The suitable optimized temperatures were adjusted from 673 K to 573 K for different compositions. The films with x< 0.40 have exhibited cubic phase with the crystalline plane of (1 1 1) orientation and for x> 0.30 have shown a hexagonal phase with (0 0 2) prominent plane. The lattice constants, crystallite size and dislocation density in the samples were estimated using X-ray diffraction data. The morphology of the films with higher Zn content exhibits fibrous structure and it changes to grain like structure on decreasing Cd concentration. XPS and EDAX analysis confirms the presence of elements in the deposits. The optical transmittance and energy band gap increased with increasing deposition temperature, whereas, decreased with increasing Cd dopant. The NLO behavior of the deposits indicates free carrier absorption induced two photon absorption processes. All deposits have shown n-type electrical conductivity. The film resistivity decreases with increase in deposition temperature and Cd content. The obtained Zn1-xCdxS films are suitable for device application of gas sensor and optical limiter.

Synthesizing of ZnS and ZnO nanotubes films deposited by thermal evaporation: morphological, structural and optical properties

ZnS and ZnO Nanotubes films have been deposited on glass and Si (100) substrates via simple thermal evaporation technique using PbS as dopant. EDX technique has been studied to examine the element’s contents. 12 wt% PbS percentage was adjusted in the prepared films to produce ZnS and ZnO Nanotubes. The XRD pattern has shown the wurtzite structure of ZnS with (002) preferred orientation, which estimated from the diffraction pattern. Morphology and thickness of the films were discovered from surface and cross section of the films, respectively, using scanning electron microscopy (SEM) images. SEM images have proved the formation of the ZnS, ZnO Nanotubes and changes of the morphology when adding PbS compared with non doped films. AFM images has been taken for a ZnS and ZnO films deposited without doping (0 wt%), and shown dens structure and demonstrated the growth of spherical forms with nanostructure (Nanotubes not created). The transparency of the prepared films has been deduced from UV spectra, where the band gap is calculated. This study, clarify the role PbS doping on the morphology and shown the formation of Nanotubes for ZnS and ZnO deposited via simple technique.

Influence of the Cation on the Surface Electronic Band Structure and Magnetic Properties of Mn:ZnS and Mn:CdS Quantum Dot Thin Films

The effects of doping Mn into ZnS and CdS quantum dots (QDs) are reported. Scanning tunneling spectroscopy spectra show a reduction in the electronic band gap in both CdS and ZnS upon incorporation of the Mn dopant. Mn:ZnS exhibits a rigid band shift toward higher bias, which is reminiscent of a hole-doping effect. This rigid band shift in Mn:ZnS is argued, with the help of X-ray photoelectron spectroscopy, to be due to a hole-doping mechanism caused by the favorable formation of Zn vacancies and a reduction in S vacancies compared to that in undoped ZnS films. In CdS, no rigid band shift is observed even though the presence of Cd vacancies can be confirmed by photoemission and magnetic measurements. A strong sp–d hybridization is observed in the Mn:CdS film upon introduction of the Mn dopant. d0 ferromagnetism is observed in both undoped ZnS and CdS QD thin films at room temperature. Upon doping of Mn into ZnS, the magnetization is reduced, suggesting an antiparallel alignment of Mn–Mn or Mn–Zn vacancy n...

Effect of low temperature vulcanization time on the structure and optical properties of ZnS thin films

The ZnS films were prepared by vulcanizing the sputtered Zn films at 440°C for different vulcanization time. The crystal structure, surface morphology, microscopic defects and optical properties of the samples were measured by XRD, SEM, slow positron beam Doppler broadening spectroscopy and UV–visible spectrophotometer, respectively. The results show that the vulcanization time has significant effect on the crystallinity and optical properties of the samples. As the vulcanization time increases, the crystallinity of the samples will be improved. But excessive vulcanization time makes the sample crystallinity weak. The transmittance of all samples in the visible range is above 60%. The crystallinity of the sample after 6 h vulcanization is the best, and the band gap value is also up to 3.49 eV. The samples form hexagonal ZnS, whose surface free energy is the lower. The effect of grain specific surface area and S vapor atmosphere on grain growth is also discussed. The slow-positron beam Doppler broadening test results intuitively reveal the changes of microscopic defects in the ZnS film, which are consistent with the results of XRD and SEM analysis.

Combinatorial Tuning of Structural and Optoelectronic Properties in CuxZn1−xS

Summary P-type transparent conductors (TCs) are important enabling materials for optoelectronics and photovoltaics, but their performance still lags behind n-type counterparts. Recently, semiconductor CuxZn1−xS has demonstrated potential as a p-type TC, but it remains unclear how properties vary with composition. Here, we investigate CuxZn1−xS across the entire alloy space (0 ≤ x ≤ 1) using combinatorial sputtering and high-throughput characterization. First, we find a metastable wurtzite alloy at an intermediate composition between cubic endpoint compounds, contrasting with solid solutions or cubic composites (ZnS:CuyS) from the literature. Second, structural transformations correlate with shifts in hole conductivity and absorption; specifically, conductivity increases at the wurtzite phase transformation (x ≈ 0.19). Third, conductivity and optical transparency are optimized within a "TC regime" of 0.10

Role of low-cost non-toxic MgCl2 treatment on ZnS films: Optimization of physical properties for buffer layers

The polycrystalline thin films comprise grain boundaries which act as recombination centres that may be passivated by chloride treatment. The conventional CdS and CdCl2 are very famous as optical window and chloride treatment in solar cells respectively, while both are expensive and severely mutagenic. Therefore in this paper, we report MgCl2 treatment on ZnS films, which is a low-cost noncarcinogenic alternative. ZnS thin films were grown on glass and ITO substrates using e-beam evaporation method, treated with MgCl2 and further thermally annealed to optimize physical properties. Films are found amorphous in nature having transmittance of about 95% and band gap increased up to 3.95 eV with annealing. Surface roughness is increased and proper ohmic behaviour is found for 300 °C treated films and EDS pattern ensured the deposition of ZnS films. To minimize the environmental risk and to reduce cost, our results exhibit that CdS optical window may be easily substituted by MgCl2 treated ZnS buffer layer.

Enhancement of efficiency of second-harmonic generation from MoS2 monolayers in 1D Fibonacci photonic crystals

In this article, the increase of the efficiency of second-harmonic generation (SHG) from MoS2 monolayers embedded in different one-dimensional Fibonacci photonic crystal structures is investigated. The systems contain ZnS, SiO2, and MoS2 layers with the same thickness of ZnS and SiO2 films, which are arranged on the basis of different Fibonacci sequences. The transfer matrix method is used to calculate the forward and backward SHG efficiencies in the undepleted pump approximation. The thicknesses of the ZnS and SiO2 films are changed to obtain the maximum frequency conversion in different structures. Tuning the thicknesses causes the second-harmonic waves generated in each MoS2 monolayer to interfere constructively. Also, the fundamental and second-harmonic wavelengths are both located at the photonic band gap edges, where the density of electromagnetic modes and the nonlinear interaction time are enhanced. Our results show that the SHG efficiencies were increased in quasiperiodic photonic crystals with respect to the periodic structure with the same number of MoS2 layers. In Fibonacci photonic crystal structures there are more geometrical parameters that can be tuned to obtain the highest efficiencies. Furthermore, we used a Bragg mirror at one side of each structure to control the propagation direction of the generated second-harmonic waves and to decrease the backward waves, which led to enhancement of the forward waves.