TRANSMISSION ELECTRON MICROSCOPY ANALYSIS OF COPPER ZINC SULPHIDE THIN FILMS

The compact and uniform Zinc Sulphide (ZnS) thin films were prepared by using chemical bath deposition (CBD) and ultrasonic chemical bath deposition (UCBD) techniques. Zinc Sulphate and Thiourea are used as precursors, whereas hydrazine hydrate played the role of complexant. The samples were further characterized to study physical, structural, optical, morphological, and compositional properties. XRD results confirmed the formation of nanocrystalline ZnS thin films with cubic structure. Optical absorption and photoluminescence study revealed the bandgap and defect levels present in the sample prepared by UCBD and CBD technique. Compact, very well adhesive films close to stoichiometry are obtained by both the techniques.

Zinc Sulphide is one of most studied semiconductor with wide band gap (3.5–3.9 eV) versatile material due to its physical and chemical properties. ZnS is a non-toxic material and a suitable candidate to be a buffer layer for heterojunction solar cells. In this study, Zinc Sulphide (ZnS) thin films were deposited by chemical bath deposition technique using Zinc Acetate Dihydrate [Zn (CH3COO)2. 2H2O] and Thiourea [CH4N2S]. The ZnS thin films samples were characterized by UV-Vis NIR Spectroscopy, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDX), Fourier-Transform Infrared Spectroscopy (FTIR) and Thin-Film Measurement Instrument. FTIR spectra confirmed the presence of ZnS bond in the crystalline thin film. XRD data confirmed the cubic structure of the deposited thin film only when the amount of Thiourea was increased and the complexing agent Hydrazine Hydrate was replaced with Tri-Sodium Citrate. Crystallite size and strain were estimated using Debye-Scherrer model and Williamson-Hall model and lattice constant was estimated using Nelson-Riley plot. Otherwise, XRD showed the amorphous phase. UV-Vis data confirmed ZnS thin films as enough transmittive and it showed higher bandgap. Thin-Film Measurement Instrument was used to measure the thickness of the ZnS thin films. Synthesized ZnS thin films exhibited promising characteristics for using as the buffer layer of the heterojunction solar cells. Highlights • ZnS thin films were prepared successfully by simple, low cost and environment friendly chemical bath deposition method. • XRD measurement confirmed both Amorphous and Crystalline phase of ZnS thin films. • By changing the precursor only can be achieved crystalline phase from amorphous phase of ZnS thin film. • The amount of precursor and deposition conditions can be optimized to produce crystalline ZnS thin film.

Zinc sulfide (ZnS) thin films have been prepared by chemical bath deposition followed by thermal annealing. The influence of sulphur (S) pressure on the morphological, structural and optical properties of the ZnS thin film has been investigated. The results show that the annealed ZnS thin films have more homogeneous morphology and better crystallinity compared with the as-deposited film. It was found that the crystallinity and mean grain size of ZnS films increase with the S pressure. Meanwhile, the transmittance of the film was significantly enhanced in the visible spectrum region with the increase of S vapor pressure, which may be attributed to the lower defects density of the film annealed at higher S vapor pressure. However, the optical band gap of ZnS thin films decrease with the increase of S pressure, which is associated with the larger grain size and higher crystallinity. The decreased band gap can adjust the conduction band offset of the buffer/absorber heterojunction in copper based semiconductor material (such as Cu(In,Ga)Se2, Cu(In,Ga)S2 or Cu2ZnSnS4)solar cell to a lower energy barrier to enhance the electron injection from absorber to ZnS buffer layer. According to the structural and optical properties analysis, the obtained ZnS thin films annealed at higher S pressure can potentially be used as better buffer layer of thin film solar cells.

Preparation and characteristics of chemical bath deposited ZnS thin films: Effects of different complexing agents

Zinc sulfide thin films were deposited on optical glass substrates by using chemical bath deposition (CBD) technique that contain solutions of thiourea, zinc acetate, ammonia and sodium citrate. The deposition time were varied from 18 hours to 39 hours. SEM, XRD, and UV-Vis-NIR were used to characterize the sample which shows that the films are thicker and the grains sizes are bigger as the deposition time increases. X-ray diffraction (XRD) pattern prove that ZnS thin films are in disordered since it does not revealing any peaks and the surface of ZnS thin films are amorphous. UV-Vis spectra showed that the deposited ZnS thin films have more than 100% transmittance in the visible region and direct band gap of deposited films are in range of 2.45 eV to 3.53 eV. Time increasing of deposition will slightly decrease the transmittance of the film.

Effect of different complexing agents on the properties of chemical-bath-deposited ZnS thin films

Zinc sulfide (ZnS) thin films deposited by chemical bath deposition (CBD) technique have proved their capability in a wide area of applications including electroluminescent and display devices, solar cells, sensors, and field emitters. These semiconducting thin films have attracted a much attention from the scientific community for industrial and research purposes. In this article, we provide a comprehensive review on the effect of various parameters on various properties of CBD-grown ZnS films. In the first part, we discuss the historical background of ZnS, its basic properties, and the advantages of the CBD technique. Detailed discussions on the film growth, structural and optical properties of ZnS thin films affected by various parameters, such as bath temperature and concentration, deposition time, stirring speed, complexing agents, pH value, humidity in the environment, and annealing conditions, are also presented. In later sections, brief information about the recent studies and findings is also added to explore the scope of research work in this field.

In this chapter, we describe the usefulness of chemical bath deposition (CBD) technique to produce high-quality thin films of cadmium sulfide for large-scale applications. In terms of operation, CBD offers unique blend of cost-effectiveness and rapid deposition rate of thin films with controlled morphology and crystallite size. Compared to other expensive thin films deposition techniques, this strategy involves the use of low-cost precursors, solvents and ambient conditions or mild temperature (up to 70 °C). Here, we explain the fundamentals of CBD with emphasis on growth mechanisms in CBD and influence of key parameters like temperature, reaction time, substrates type, and solvent to grow high conformal thin films for technological grade.

Influence of magnesium dopant on ZnS thin films by low-cost chemical bath deposition technique

Zinc sulphide (ZnS) thin films with nanoscale grains of about 8–113 nm were deposited on glass substrates by chemical bath deposition technique using aqueous solution of zinc acetate [Zn (CH3COO)2] and Thiourea. The structure, surface morphology and optical characteristics of the deposited films were investigated for photovoltaic device applications. The crystallinity of the thin films was characterised by X-ray diffraction and they all appeared to be polycrystalline. Scanning electron microscopy (SEM) studies gives the average grain size to be small (8–130 nm) with an uneven surface feature. Fourier transform infrared spectroscopy (FTIR) and UV–VIS measurements showed that the films had more than 65% transmittance in the wavelength larger than 350 nm. The fundamental absorption edge shifted to a shorter wavelength, which corresponds to an increase in the energy band gap ranging from 3.59 to 3.72 eV. The physical conditions were kept identical while growing all the samples. It was found that ZnS films are suitable for use as the buffer layer of CIS solar cells, and it is a viable alternative for replacing CdS in the photovoltaic cell structure.

Zinc Sulfide (ZnS) thin film was deposited on glass substrate using chemical bath deposition technique and Tin (Sn) doping was performed by adding Tin Chloride (SnCl 2 ) solution as Sn source. These films were further characterized by X-ray diffractometer (XRD) and UV-VIS-NIR spectrophotometer. ZnS thin film had single phase hexagonal structure and Sn doping replaces Zn atom without altering shape. Deposition temperature fixed at 70°C for 30 minutes and annealed for 15 minutes at 100°C. XRD intensity increase as the percentage of Sn doping increases, Optical properties like transmittance, dielectric constant, energy bandgap and absorbance had promising results. Transmittance in near-infrared region was greater than 83%, relatively stable absorbance of (5–11) %, energy bandgap from 3.60 eV to 3.84 eV, small fluctuation in dielectric constant and reduced refractive index. Optical bandgap and dielectric constant of ZnS thin film both have proportional relation with percentage of Tin doping.

Semiconducting Zinc Sulphide (ZnS) thin films were deposited on glass substrate using relatively simple Chemical Bath Deposition (CBD) technique. Nano crystalline ZnS thin films were fabricated in the study. Optical characterization of the films showed that the materials are transparent to visible light, opaque to ultraviolet radiation and near infra red radiation. The electrical conductivity decreases as the energy increases while the optical conductivity increases gradually over an energy range, and then sharply afterward. The XRD pattern showed that the deposited ZnS had distinct peaks at 31.59, 32.21, 44.76 and 46.73o respectively with 101, 110 and 111 preferred orientations. The energy band gap of ZnS film was found to be between 3.20–3.70eV with a direct band gap transition. These properties make ZnS thin films find useful applications as cover plates for solar energy panels and materials in the fabrication of semiconductor devices. In addition, the films were found to exhibit switching potentials.Keywords: Electrical, Optical, Solid state properties, ZnS

Aluminum antimonide (AlSb), a semiconductor compound, finds its applications in optoelectronics because of its tunable bandgap and promising properties achieved by tailoring suitable dopants. To explore the effects of doping, thin films of pure AlSb and 10% magnesium (Mg)-doped aluminum antimonide (MgAlSb) were synthesized through compound solution deposition on a glass substrate using a low-cost chemical bath deposition (CBD) technique at varying bath temperatures with deposition time intervals ranging from 60 to 180 min. Optical microscopy was used to evaluate the surface roughness and morphology of the synthesized films, revealing the surface roughness and thin film uniformity at different deposition times. The structural characteristics of AlSb and Mg-doped AlSb thin films were further examined using the X-ray diffraction technique, which validated the formation of AlSb and Mg-doped AlSb thin films. This research enables large-scale low-temperature deposition for a variety of conceivable applications in the coatings, materials penetration, energy, and photonic sectors due to the novel properties of this material.

Investigations on the physical properties of the polycrystalline ZnS thin films deposited by the chemical bath deposition method

The effect of deposition parameters of CdS thin films developed by Chemical Bath Deposition (CBD) technique was investigated in this paper. We studied the influence of pH control of the reaction solution on the structural and optical properties of chemically deposited CdS films. Different films thicknesses of CdS were deposited onto a glass substrate. The structural surface morphology of as-deposited CdS thin films was characterized by SEM, XRD, profilometer, and ultraviolet–visible spectroscopy. The physical conditions were kept identical while growing the samples. The investigation of the effect of the synthesis method on the change the ammonium hydroxide by buffer pH-11 contributed in increases the growth kinetics, resulting in thicker films. Over the years, thin films of II-VI semiconductor compounds are most promising for utilization in solar cells, out of which the cadmium sulfide (CdS) has received intensive attention, since its band gap lie very close to the range of maximum theoretically attainable energy conversion efficiency. CdS is an inorganic compound of yellow solid color, and due to its wide band gap, photoconductivity, and high electron affinity, is known to be an excellent heterojunction partner for p-type cadmium telluride, p-type copper indium diselenide. It has been widely used as a window material in high efficiency thin film solar cells based on cadmium telluride or copper indium diselenide [1-3]. In these devices, light penetrates the CdS layer and it is absorbed in the p-type semiconductor close to the pn junction. Also, CdS is an interesting crystal material in the area of photodetectors, semiconductor lasers, and non linear integrated optical devices. The importance of wide band gap materials is related to the possibility of fabricating light emitting diodes or laser heterostructures for emission in the visible spectral range. The CdS thin films were fabricated by CBD technique on glass substrate. The diffractogram of an