Papers by Keyword: ZnS

Abstract: 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.

Abstract: Among the second-generation solar cells, thin-film solar cells based on CIGS, CZTS and CdTe are well known due to their higher efficiencies, low cost and simple fabrication techniques. In this proposed work, we are committed to developing CZTS and ZnS thin films for second-generation thin-film photovoltaics. CZTS and ZnS have energy band gap of 1.4-1.5 eV and 3.6 eV, while their light absorption coefficients are 10⁴ cm^-1 and 3.3×10⁴ cm^-1 respectively. In thin film solar cells, absorber layer consists of photovoltaic material that should have optimal bandgap close to 1.34 eV. Moreover, a wide band gap window layer acts as p-n junction with absorber layer. In this work, we are reporting the synthesis of CZTS and ZnS thin films via wet chemistry route using spin coating method. Deposition of thin films on SLG substrate were carried out at specific process parameters such as spinning speed, concentration of precursors and annealing temperature to get the optimized thin film suitable for photovoltaic applications. Surface morphology and elemental compositional analysis investigated through SEM and EDX spectroscopy respectively. Electrical and optical properties were examined via Hall effect measurements and UV-VIS NIR spectrophotometry respectively. In addition micro-chemical and functional group analysis were conducted by FRIT spectroscopy. Keywords: Thin film PV, wet-chemistry, CZTS, ZnS

Abstract: The deposition of Zinc Sulfide (ZnS) thin films is optimized using a radio-frequency (RF) magnetron sputtering technique with variable RF power to minimize deposition steps and lower the fabrication costs. Room temperature as-deposited film growth optimization is conducted by studying their structural, morphological, optical, and electrical properties. The target power and deposition rate were related by a slope of 0.1648 and a linear correlation coefficient (R) of 0.9893. Only one significant peak for the films in the XRD pattern indicated that the films are of a single crystalline structure. All the deposited thin films exhibited a ZB structure. It is observed that the micro-strain ranged from 36.00x10^-3 to 4.14x10^-3, and that of dislocation density ranged from 6.68 to 0.08 Line/cm². The optical energy band gaps of as-deposited ZnS films at different deposition power were found from 3.31 to 3.37 eV. The average transmittance percentage was increasing from 71.63% to 84.29%, above 400 nm wavelength. The films exhibited n-type conductivity with bulk carrier density in the order of 10¹² cm^-3. The carrier concentration and mobility ranged from 2.84x10¹¹ to 3.98x10¹² cm^-3 and 1.06 to 27.68 cm²/Vs, respectively. The minimum and maximum resistivity of 1.01x10⁴ and 2.52´10⁵ Ω-cm were noted for the film deposited at 90 and 60W power, respectively.

Abstract: In the present study, Zn_xSn_1-xS (x = 0, 0.25, 0.5, 0.75 and 1) thin film samples were deposited by ultrasonic spray pyrolysis technique on glass substrates at 350°C to investigate the effect of variation of Zn concentration (x) on the structural, morphological, optical and electrical properties of Zn_xSn_1-xS thin films. The films were deposited by varying Zn content in the starting solution. The films deposited were found to be amorphous having root mean square (RMS) roughness ranged from 18.2 to 93.5 nm. The optical characterization by UV-Vis spectroscopy showed that the transmittance and reflectance of all samples are lower than 12.2 % and 10 % respectively. The optical band gap was estimated from the reflectance and transmittance spectra are about 3.86 eV. The carrier mobility is ranged from 113 to 2600 cm²/v.s.

Abstract: Multi-angular branched ZnO microstructures with rods-shaped tips and nanopushpins with hexagonal cap on top have been synthesized by a simple thermal treatment process of compacted ZnS powder used as starting material and substrate. The structures have been grown at different temperatures (800, 900 and 1000 °C) for 60 min, in a constant nitrogen environment at atmospheric pressure via a catalyst-free process. XRD results of the as-grown products from ZnS powder show a significant reduction in the cubic zincblende phase to the hexagonal wurtzite phase with the increase of treatment temperature, as compared to the bulk value. Post-anneal analyses indicated that the transformation of morphologies of the as-grown structures also depends strongly on the treatment temperature. The proposed method represents an easy and economical way to grow complex structures of ZnO, with a relatively short time, furthermore, without the neediness of use an external substrate to grow. These new and interesting nanostructures have potential in applications such as optoelectronics.

Abstract: The nonlinear absorption and nonlinear refraction properties of water soluble ZnS semiconductor quantum dots are studied by using Z-scan technique with the action of 400 nm and 532 nm femtosecond laser pulses. The experimental results show that the three order nonlinear effect of ZnS semiconductor quantum dot is stronger in 400 nm laser pulse, and it is weaker in 532 nm laser pulse. The three order nonlinear polarization coefficient of ZnS semiconductor quantum dot is 4.58×10^-13 esu with the action of 400 nm laser pulse, it is 9.22×10^-14 esu with the action of 532nm laser pulse. The ZnS semiconductor quantum dot has a relatively good three order optical nonlinear effect with the action of 400nm wavelength laser pulse.

Abstract: Phosphorus-doped p-type ZnS NWs were synthesized by chemical deposition method. The as-synthesized NWs shows obvious p-type conduction with a hole concentration of 8.35 × 10¹⁷ cm^-3. ZnS-Si core-shell nanoheterojunction was fabricated by depositing Si thin film on the surface of ZnS NWs through a sputtering method. The core-shell nanostructure exhibited excellent photoresponse to white light and UV light. Under UV light illumination, a high performance with a responsibility of ~ 0.14 × 10³ AW^-1, a gain of ~ 0.69 × 10³ and a detectivity of ~ 1.2 × 10¹⁰ cmHz^1/2W^-1 were obtained based on the ZnS-Si core-shell nanoheterojunction. This new nanostructure is expected to play an important role in the next-generation optoelectronic devices.

Abstract: To increase the industrial applicability of hypereutectic Al-Si alloys, various methods have been used to refine primary silicon. The addition and refinement effects of phosphorus (P), rare earth metals (RE) on primary Si have been studied widely, But they have been testified be with some disadvantages, that is, the pollution to the environment of P and the high cost of RE, etc. Now, a new refiner - ZnS and the corresponding processing technology were researched. Microstructures of hypereutectic Al-Si alloy (Si wt. 24%) with fine primary Si were successfully obtained. And the primary Si can be refined from more than 80μm to 20μm. And the distribution of primary silicon is getting more uniform.

Abstract: Wurtzite three-dimensional ZnS nanostructure has been synthesised under low temperature (180°C) via solvothermal method in mixed solvents of ethylenediamine and ethylene glycol. The phase structure, morphology and optical properties have been characterized by X-ray (XRD), scanning electron microscope (SEM) and photoluminescence spectra (PL). Through the change of reaction time and the mixed solvent ratio, the properties of three-dimensional ZnS have been discussed in this paper.

Abstract: ZnS/TiO₂/Chitosan nanocomposite thin films were prepared by entrapping zinc ions and nanosized TiO2 in chitosan films under mild conditions. The surface structure and morphology of the film were characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Methyl Orange was selected to evaluate the photocatalytic activity under simulated solar irradiation. The HRTEM results show that TiO2 and ZnS were dispersed uniformly with diameters of 20–30 nm. The prepared film exhibits high photocatalytic activities. About 93.5% Methyl Orange(3.6×10-5 mol/L) were photodegraded by 0.6 g L−1 photocatalyst at pH 4.0 with 120 min irradiation. The influence of the reaction pH, stability and reusability of the film have also been investigated. It can be developed as a economically feasible and environmentally friendly photocatalyst for the practical industrial waste water treatment.