Nanocrystalline Cadmium Sulfide Thin Films Research Articles

Synthesis and characterization of cadmium sulfide (CdS) thin films by cyclic voltammetry technique

Abstract Nanostructure (II-VI) semiconductor Cadmium Sulfide (CdS) have interesting due to their in scientific circle and varieties of encouraging potentials in extensive applications such as transparent windows, photoluminescence devices, sensors, solar cells, etc. In this work, nanocrystalline CdS thin films (TFs) synthesized on the Indium tin oxide (ITO) coated glass substrate via cyclic voltammetry (CV) with a three-electrode deposition technique. X-Ray Diffractometer (XRD) used for the structural study of TFs and the topographical image characterized by using an Atomic Force Microscope (AFM). XRD patterns of the TFs were shown that nanocrystaline in nature with a cubic structure at (2 0 0) as the preferential orientation. Chemical compositions of the deposited TFs analysed by using Fourier Transform Infrared Spectroscopy (FT-IR). The optical properties of CdS TFs characterized by using a UV–Vis spectrophotometer showed that the optical band gap energy (Eg) decreases from 2.92 eV to 2.28 eV with increasing of deposition time from 15 min to 60 min respectively. Urbach energy increases from 117 meV to 151 meV with increasing of deposition time from 15 min to 60 min respectively.

Microstructural, optical and electrical properties of CdS thin films grown by spray pyrolysis technique as a function of substrate temperature

In this research, nanocrystalline cadmium sulfide thin films were produced by the spray pyrolysis technique on glass substrates. The effects of substrate temperature in the range 400–550 °C on the structural, morphological, optical, and electrical properties of the thin films were investigated. The thin films have been characterized by investigating their X-ray diffraction, field emission scanning electron microscope (FE-SEM), and optical absorption (UV–Vis) measurements. X-ray analysis revealed that thin films were a polycrystalline structure with the hexagonal phase in all cases and by increasing in substrate temperature, crystallite size decreases, and dislocation density increases. The FE-SEM images showed that the surface of the thin films is uniform, homogeneous and without cracks. The average sizes of the grains are at the range of 210–235 nm. The obtained values for optical band gap have been in the range of 2.18–2.41 eV, where the value of optical band gap for the thin films decreases by increasing substrate temperature. The Urbach energies of the thin films increase as the substrate temperature is increased. When substrate temperature increased from 400 to 550 °C, electrical resistivity increased from 531 to 2817 Ω cm, carrier concentration decreased from 15.96 × 1014 to 3.71 × 1014 cm−3, Hall mobility decreased from 7.37 to 5.98 cm2/V s. Hall effect analysis indicated that the thin films exhibited n-type conductivity.

Resonant Raman scattering in nanocrystalline thin CdS film

Resonant Raman scattering is highly desired for material study. It is experimentally not easy to reach the resonant scattering interaction between an incident photon and a material due to the limited available laser wavelengths. In this study, by employing silver plasmonic nanoparticles deposited on glass substrate and by in situ adjusting the cadmium sulfide (CdS) band gap through heat treatment, resonant Raman scattering condition (laser wavelength of 514.5 nm) was fully achieved in nanocrystalline CdS thin films. The dramatically enhanced Raman scattering allowed us to in situ monitor the phase transition that occurred during the heat treatment and to quantitatively characterize the fraction of the zincblende (cubic) CdS in the main base of wurtzite (hexagonal) CdS. Raman multi-phonon and the corresponding high-order scattering modes were observed due to the much enhanced surface nanoplasmonic electric field. Copyright © 2016 John Wiley & Sons, Ltd.

English

Nanocrystalline Cadmium sulfide (CdS) thin films were prepared by chemical bath deposition technique on a glass substrates at  a temperature of 80°C  and at different deposition times with composition of cadmium chloride (CdCl2), thiourea (CS (NH2)2), ammonia solution (NH4OH) and triethanolamine (TEA) solution. The characterization of thin films was carried out for the structural, morphological and optical properties using X-ray diffraction (XRD), Scanning electron microscope (SEM) and UV-VIS spectrophotometer. XRD studies show that the preferential orientation (002), analysis shows that the prepared samples have hexagonal crystal structure. Scanning electron microscopy (SEM) reveals small nanosized grains tied up in a fibrous-like porous structure uniformly distributed over the surface of the substrate for the CdS films. A UV-VIS optical spectroscopy study was carried out to determine the band gap of the nanocrystalline CdS thin films. The average band gap was found to be 2.25 eV, which is lower than the bulk value (2.4 eV). The increase in absorption coefficient with photon energy makes the deposited CdS thin film a suitable candidate for the fabrication of solar cells.   Key words: Nanocrystalline Cadmium sulfide (CdS), X-Ray diffraction, scanning electron microscopy, solar energy.

Characterization and antibacterial capabilities of nanocrystalline CdS thin films prepared by chemical bath deposition

Antibacterial capabilities of nanocrystalline cadmium sulfide (CdS) thin films have been developed against Gram-positive and Gram-negative bacteria in dark and sunlight at 60°C. For this purpose, a strain of Gram-positive Staphylococcus aureus, and two strains of Gram-negative bacteria (Pseudomonas aeruginosa, and Escherichia coli) were used. The nanocrystalline CdS thin films have been prepared using a chemical bath deposition (CBD) method at different thicknesses (50, 80 and 100nm). The different deposition parameters including the speed of rotation of substrate, temperature of chemical bath, pH of solution and time of the deposition were optimized. The Polyvinylpyrrollidone (PVP) was successfully used as capping agent in order to stop the agglomeration in the CdS thin films. It was found that, CdS thin films have remarkable antibacterial activity in dark and sunlight and it could be applied as antimicrobial agent in medical field. In order to confirm the crystalline structure of CdS thin films, the polycrystalline nature of the deposited CdS thin films with hexagonal structure was obtained. Furthermore, the structural parameters including lattice parameters, cell volume, the space group, average grain size, dislocation density and the strain have been calculated. The topography and surface roughness of the CdS thin films have been studied before and after the bacteriostatic effect using Scanning Electron Microscopy (SEM). Furthermore, the compositions of nanocrystalline CdS thin films have been evaluated using Energy Dispersive X-ray emission (EDX) and a Transmission Electron Microscope (TEM). Based on the optical measurements in the range of 300–2500nm, the band gap energy of the prepared CdS thin films was found to be 2.4eV.

Fabrication and characterization of nanocrystalline CdS thin film-based optical sensor grown via microwave-assisted chemical bath deposition

Highly uniform nanocrystalline cadmium sulfide (CdS) thin films were successfully deposited on Si (111) substrates by microwave-assisted chemical bath deposition technique. Cadmium chloride (CdCl2) and thiourea [SC(NH2)2] precursors with different molar concentrations were used to prepare nanocrystalline CdS thin films. The effect of the molar concentration of reagents on the quality of the deposited thin films was investigated. Structural and morphological studies revealed that the quality of the grown CdS thin films was significantly affected by molar concentrations of reagents. Optimal thin film quality was utilized to fabricate a nanocrystalline CdS-based optical sensor. Current–voltage measurements (I–V) for the fabricated device showed significant sensing to low-power (0.3mW/cm2) 500nm light. The device exhibited high responsivity of 0.65AW−1 at 3V applied bias. Time response measurements showed rapid response and baseline recovery under low applied bias voltage, indicating good quality of the deposited thin film. A simple and low-cost method to fabricate a low-power, highly photosensitive optical sensor was introduced.

Characterization of Nanomaterials

Nanomaterials have attracted attention because of their unique physical, chemical, and mechanical properties that differ from those of bulk solids and molecules. Nanomaterials exhibit distinct sizedependent properties in the 1–100 nm range where quantum phenomena are involved. That is, when the particle radius approaches the asymptotic exciton Bohr radius, the influence of quantum confinement becomes apparent. The very large surface area of nanomaterials is one of the reasons for their novel properties and the high surface-to-volume ratio results in high significant effects of surface properties on their structure. Intensive research is being done for the use of nanomaterials in many applications such as energy storage, energy conversion, solar cells, pharmaceuticals, life science applications, optoelectronics, sensing and actuation nanosystems, catalysis, and composite materials. The techniques that can be used to characterize nanomaterials include electron microscopy, scanning probe microscopies especially, atomic force microscopy, x-ray diffraction, neutron diffraction, x-ray scattering, x-ray fluorescence spectrometry, acoustic wave technique, contact angle measurements, and various spectroscopies. The following articles describe the production and characterization of different types of nanomaterials, where the morphological, structural, and mechanical properties are determined and discussed. In the article, ‘‘Boron-Doped Strontium-Stabilized Bismuth Cobalt Oxide Thermoelectric Nanocrystalline Ceramic Powders Synthesized via Electrospinning’’ by S. Kocyigit et al. both boron-undoped and boron-doped thermoelectric strontium-stabilized bismuth cobalt oxide nanocrystalline ceramics are produced by an electrospinning technique. The powders are characterized by using x-ray diffraction, scanning electron microscopy, and physical properties measurement system techniques. The structural and thermoelectric properties of the produced powders are evaluated and the effects of boron doping on the thermoelectric capacity of materials are also determined. In the next article, ‘‘Singleand Two-Layer Coatings of Metal Blends onto Carbon Steel: Mechanical, Wear, and Friction Characterizations’’ by B.S. Yilbas et al., singleand two-layer coatings of metal blends onto carbon steel are produced using a high-velocity oxyfuel (HVOF) deposition gun. The wear and friction resistance of super alloy powder coatings are investigated. The surface mechanical properties and the nanomechanical properties of singleand two-layer coatings are measured using the nanoindentation technique. The residual stresses formed on the surface of the coatings are measured using the x-ray diffraction technique. They found that the mechanical properties, friction, and wear resistance of the two-layer coating are similar to that of the single-layer coating. The synthesis and characterization of new and novel nanomaterials with well-controlled structures, crystalline phases, shapes, sizes, and porosities are very important for breakthroughs in several technologies. The challenge for the so-called nanotechnologies is to achieve perfect control of nanoscale-related properties. This obviously requires correlating the parameters of the synthesis process with the resulting nanostructure. In the article, ‘‘Tuning the Properties of Nanocrystalline CdS Thin Films’’ by S.J. Ikhmayies, a review of the experimental methods for tuning the properties of nanocrystalline CdS thin films is performed. Nanocrystalline cadmium sulfide (CdS) thin films are of potential use in the technology of CdS/CdTe solar cells, photonics, detectors, and computing devices. Nanomaterials can be used to improve or change the properties of some products, alloys, and composites. In the work, ‘‘Effects of Al2O3 Nanopowders on the Wear Behavior of NiTi Shape Memory Alloys’’ by Y. Sahin and K.E. Oksuz, the authors prepared TiNi shape memory alloy and its composShadia J. Ikhmayies is the guest editor for the Materials Characterization Committee of the TMS Extraction & Processing Division, and coordinator of the topic Characterization of Nanomaterials in this issue. JOM, Vol. 66, No. 1, 2014

Tuning the Properties of Nanocrystalline CdS Thin Films

Tuning the properties of nanocrystalline cadmium sulfide (CdS) thin films is very important in the technology of photonics, detectors, and computing devices. This can be achieved through the appropriate selection of the synthesis techniques, types and concentrations of the chemicals, deposition parameters, and postdeposition heat treatments. In addition, control of the properties can be achieved by controlling the size, structure type, and surface states of the nanocrystallites without altering the chemical composition of the films. A review of the experimental methods for tuning the properties of nanocrystalline CdS thin films is performed. Although control of these variables is a complicated process, high-quality nanocrystalline CdS thin films with optimum structural, morphological, and optical properties have been produced by different authors.

Structural and optical properties of nanocrystalline CdS thin films prepared using microwave-assisted chemical bath deposition

Cadmium sulfide (CdS) nanocrystalline thin films were prepared using the microwave-assisted chemical bath deposition method onto glass substrates at 80°C. Aqueous solutions of either cadmium chloride or cadmium acetate and thiourea were used as sources of Cd2+ and S2− ions, respectively. Two sets of samples with different concentrations were prepared. A microwave oven was used as a heating source to synthesize the nanocrystalline CdS thin films. The prepared thin films had a good adhesion with no pinholes. These films were examined for their structural and surface morphologies by X-ray diffraction (XRD), scanning electron microscopy, and atomic force microscopy. The optical properties were investigated using UV–vis spectrophotometer, photoluminescence, and Raman spectroscopy. Particle size values obtained from XRD were compared with these calculated using effective mass models. The values of optical band gaps according to optical transmission measurements decreased as the ion source molar concentration increased.

Optical and Structural Properties of Nanocrystalline CdS Thin Films Grown by Chemical Bath Deposition

Nanocrystalline cadmium sulfide thin films are prepared using chemical bath deposition (CBD) technique in aqueous alkaline bath at 60 °C and their subsequent condensation on glass substrates. Effects of annealing on structural, morphological and optical properties are presented and discussed. The best annealing temperature for CBD grown CdS films is found to be 350 °C from optical properties. The optical and structural properties of CdS films are found to be sensitive to annealing temperature and are described in terms of XRD, SEM, transmission spectra and optical studies. The structural parameters such as crystallite size have been evaluated through XRD while SEM micrographs exhibit ordering of grains upon annealing. The transmission spectra shift towards higher wavelength upon annealing indicating increase in crystallinity. Annealing over 350 °C is found to degrade the external structure and optical properties of the film.

Structural, Optical and Photoconductive Properties of Chemically Deposited Nanocrystalline CdS Thin Films

Nanocrystalline cadmium sulphide (CdS) thin films were prepared using chemical bath deposition (CBD), and the structural, optical and photoconductive properties were investigated. The crystal structure of CdS thin film was studied by X-ray diffraction. The crystallite size, dislocation density and lattice constant of CBD CdS thin films were investigated. The dislocation density of CdS thin films initially decreases with increasing film thickness, and it is nearly constant over the thickness of 2,500 <TEX>${\AA}$</TEX>. The dislocation density decreases with increasing the crystallite size. The Urbach energies of CdS thin films are obtained by fitting the optical absorption coefficient. The optical band gap of CdS thin films increases and finally saturates with increasing the lattice constant. The Urbach energy and optical band gap of the 2,900 A-thick CdS thin film prepared for 60 minutes are 0.24 eV and 2.83 eV, respectively. The activation energies of the 2,900 <TEX>${\AA}$</TEX>-thick CdS thin film at low and high temperature regions were 14 meV and 31 meV, respectively. It is considered that these activation energies correspond to donor levels associated with shallow traps or surface states of CdS thin film. Also, the value of <TEX>${\gamma}$</TEX> was obtained from the light transfer characteristic of CdS thin film. The value of <TEX>${\gamma}$</TEX> for the 2,900 A-thick CdS thin film was 1 at 10 V, and it saturates with increasing the applied voltage.

Photoluminescence of Nanocrystalline CdS Thin Films Prepared by Chemical Bath Deposition

Nanocrystalline cadmium sulfide (CdS) thin films were prepared using chemical bath deposition in a solution bath containing , , and . The CdS thin films were investigated using X-ray diffraction (XRD), photoluminescence (PL), and Fourier transform infrared spectroscopy (FTIR). The as-deposited CdS thin film prepared at for 60 min had a cubic phase with homogeneous and small grains. In the PL spectrum of the 2,900 A-thick CdS thin film, the broad red band around 1.7 eV and the broad high-energy band around 2.7 eV are attributed to the S vacancy and the band-to-band transition, respectively. As the deposition time increases to over 90 min, the PL intensity from the band-to-band transition significantly increases. The temperature dependence of the PL intensity for the CdS thin films was studied from 16 to 300 K. The and activation energies are obtained by fitting the temperature dependence of the PL intensity. The and are caused by the deep trap and shallow surface traps, respectively. From the FTIR analysis of the CdS thin films, a broad absorption band of the OH stretching vibration in the range and the peak of the CN stretching vibration at were found.

Effect of film thickness on the energy band gap of nanocrystalline CdS thin films analyzed by spectroscopic ellipsometry

Abstract Nanocrystalline cadmium sulfide thin films were deposited by the radio frequency magnetron sputtering technique on Si and glass substrates with different particle sizes and thicknesses by varying deposition time. X-ray diffraction and transmission electron microscopic studies confirmed the nanocrystalline cubic CdS phase formation. TEM micrographs of the films revealed the manifestation of nano-CdS phase with average particle size of 3.6–7.3 nm for different films. These nanocrystalline films were analyzed by spectroscopic ellipsometry. The optical constants and the fitting constants were obtained by fitting the ellipsometric parameter del and psi data using Forouhi and Bloomer models in the wavelength range 248–825 nm. The optical band gaps of the films were also measured by spectrophotometric studies. It was found that the energy band gap decreased from 3.28 to 2.54 eV when the film thickness increased from 153 to 205 nm.

Engineering of nanocrystalline cadmium sulfide thin films by using swift heavy ions

Swift heavy ion (SHI) irradiation experiments have been performed on as-deposited nanocrystalline cadmium sulfide (CdS) thin films by using 100 MeV Au8+ ions with 5 × 1012 ions cm−2. In addition, the as-deposited films were annealed at 300 °C in air for 1 h. Structural, optical and electrical properties of pristine (as-deposited), annealed and irradiated thin films were carried out by using x-ray diffraction (XRD), energy dispersive spectra, scanning electron microscopy, atomic force microscopy, UV-VIS spectroscopy and Arrhenius plots for resistivity and thermoemf, respectively. XRD shows the intrinsic peak of (0 0 2) for the hexagonal phase of CdS. After annealing and SHI irradiation this peak was enhanced drastically and dramatically, showing the dominant orientation in this plane. The grain growth observed in these two post-deposition processes was different. This resulted in a decrease in resistivity of the annealed and the irradiated samples by one and two orders from the pristine sample, respectively.

Conduction studies on chemical bath-deposited nanocrystalline CdS thin films

Chemically pure, stoichiometric cadmium sulphide (CdS) films were produced by the chemical bath deposition (CBD) method on suitably cleaned silicon (Si) wafer and indium–tin oxide (ITO) substrates at room temperature. The nanocrystalline film was found to be hexagonal in structure with the preferential orientation along the (0 0 2) plane. Variable-range hopping conduction through 66 nm thick CdS films on ITO substrates was found to be responsible at the low voltage while space charge-limited conduction became dominant at a relatively high bias voltage.

Optical Studies on Chemical Bath Deposited Nanocrystalline CdS Thin Films

Nanocrystalline cadmium sulphide thin films were prepared by the chemical bath (CB) deposition using a mixed aqueous solution of cadmium chloride, thiourea, and ammonium chloride. The XRD patterns showed that the CdS films were of hexagonal phase with preferred (002) orientation. From ellipsometric measurements, the film thickness was found to be in order of 66 nm and the optical band gap was estimated to be 2.4 eV.