Spherical-shaped Grains Research Articles

Insight into deposition duration-varied crystallinity, optical parameters, morphology and electrical properties of solution-processed nanostructured CdSSe thin films

Nanostructured cadmium sulpho selenide (CdSSe) films have been grown onto glass substrates for different deposition durations via a facile solution-based method known as chemical bath deposition (CBD). XRD studies revealed that the crystallites in the films possessed hexagonal (wurtzite) structures with predominant orientation along the (002) plane. The crystallite size increased from ∼5.95 nm to ∼16.69 nm with the increase in deposition duration from 1 h to 4 h. The absorbance, transmittance and reflectance measurements were carried out. A transparency of ∼(50–80) % was obtained for the films. The direct optical energy band gap was found to decrease from 1.982 eV to 1.952 eV with the increment of deposition duration from 1 h to 4 h. SEM micrographs of the films revealed the presence of nano spherical-shaped grains with an average size ranging from ∼305 nm to ∼612 nm. HRTEM images illustrated the presence of compact nano-spherical grains and nano-crystallites distributed in random orientations. Raman spectroscopy divulged the presence of CdSe and CdS vibrational Raman modes and overtones in the films. PL spectra revealed a prominent red emission band along with weak luminescent bands in the yellow-red emission region. The presence of Cd–Se and Cd–S bonds in the films was validated using FTIR analysis. Electrical investigation revealed the linear current‒voltage relationship for the films with the rise in conductivity with deposition duration. Hence, deposition duration stands out as a vital parameter for modulating the properties of CdSSe thin films for use in photovoltaic devices and optoelectronics.

Cerium-modified Bi2FeMoO6: Microstructure, dielectric and optical properties

This paper presents an extensive investigation into the synthesis and characterization of Bi2FeMo1-xCexO6 (x = 0.0, 0.06, and 0.1) double perovskite type ceramic materials, fabricated using a high-temperature solid-state reaction method. The article delves into various aspects of these materials, including their structural, microstructural, dielectric, and optical properties. Structurally, the materials exhibit a rhombohedral crystal structure, having average crystallite sizes of 49.5 nm, 21.8 nm, and 26.4 nm for the respective compositions. Scanning electron microscopy reveals a uniform distribution of cylindrical and fractured spherical-shaped grains, complemented by well-defined grain boundaries. Energy dispersive X-ray spectroscopy analysis and elemental color mapping provide concrete evidence regarding the presence of key elements, such as Bi, Fe, Mo, Ce, and O, affirming the formation of highly dense and pure samples. Dielectric properties are comprehensively characterized across a wide temperature range of 25 °C to 500 °C and frequency range of 1 kHz to 1 MHz, highlighting the occurrence of the Maxwell-Wagner polarization effect at lower frequencies. The impedance study underscores the pivotal role of both grains and grain boundaries in determining the conductivity mechanism, with the x = 0.1 composition exhibiting superior semiconducting characteristics. Further examination of the modulus study and AC conductivity supports this finding. Additionally, the calculation of thermal activation energy suggests that the x = 0.1 composition boasts a more favorable thermally activated relaxation mechanism, rendering it a promising candidate for various device applications. Finally, an assessment of the UV–visible spectra reveals that the x = 0.1 composition possesses an ideal bandgap energy range, making it particularly suited for advanced optoelectronic devices.

Optical and structural properties of graphene oxide-incorporated polyvinylpyrrolidone/copper ternary nanocomposites (PVP/Cu/GO) films

Novel ternary nanocomposite films based on polyvinylpyrrolidone copper nanoparticles graphene oxide (PVP/Cu/GO) were prepared using electrochemical deposition technique on Fluorine doped tin oxide (FTO) substrate. This facile and effective approach has been proven to be very useful for the fabrication of inexpensive, high-performance electrochemical devices. To achieve uniform deposition of the nanocomposite films, the three components of the nanocomposites were mixed under controlled conditions. The impact of different GO loading on the PVP/Cu/GO composites was measured using UV–visible spectroscopy, X-Ray Diffraction (XRD) spectroscopy, SEM, EDX, and four-point probe techniques to evaluate their optical, structural, morphological, compositional, and electrical properties, respectively. UV-visible analysis shows that the optical band gap (Eg) of the nanocomposite decreased from 3.51 to 2.02 eV with increasing GO loading. All of the nanocomposites showed UV absorbance of ≈450 nm. According to the XRD results, the GO materials were very well dispersed in the PVP/Cu/GO composites, while also revealing the crystalline nature of the nanocomposites. The SEM results revealed spherical-shaped grains of the deposited films, while the EDX results revealed the major elements deposited. Four-point probe analysis of the nanocomposites revealed slight increase in conductivity with low GO content, thus confirming the semiconducting properties of the nanocomposites with the GO content. The obtained results herein shows that the PVP/Cu/GO nanocomposites are successfully synthesized with attractive physiochemical properties suitable for the fabrication of organic electronic devices and photovoltaic devices.

Exploring Relaxation Phenomenon in Cu-Substituted Ba2NiWO6 Double Perovskites

Double perovskites are an emerging class of functional materials with a great deal of durability perspective owing to their inherent flexibility in cation coordination selection. Here, we synthesized pristine and Cu2+-doped Ba2NiWO6 utilizing the solid-state reaction route to investigate their structural, morphological, and dielectric behavior. Structural examination revealed the development of a cubic crystal structure for both compositions, and Cu2+ integration in Ba2NiWO6 decreases the crystallite size. The spherical-shaped grains shrink in size and start agglomeration with Cu2+ incorporation. The incorporation of Cu2+ reduces the grain size, leads to accumulation of space charges at the grain boundaries, and thus, facilitates growth in the space charge polarization. This increases the dielectric constant of the material, thus making these compositions viable for advanced miniaturized electronic devices.

Room-Temperature Ferromagnetism in Cu/Co Co-Doped ZnO Nanoparticles Prepared by the Co-Precipitation Method: For Spintronics Applications

In current work, pure ZnO and Zn0.96–xCu0.04CoxO (0 ≤ x ≤ 0.05) nanoparticles were synthesized by the co-precipitation method. Structural analysis and phase determination of the formed nanoparticles was carried out using X-ray diffraction (XRD) and Williamson–Hall plots. The hexagonal wurtzite structure was manifested by all the samples with divergent microstructures. The change in lattice parameters, bond length, dislocation density, and lattice strain indicates that Cu and Co were successfully incorporated. Average crystallite size was found to be in the range of 32.16–45.42 nm for various doping concentrations. Field emission scanning electron microscopy results exhibited that the surface morphology is an amalgam of spherical-like and hexagon-like structures. Spherical-shaped grains were homogeneous and evenly distributed all over the structure. Fourier transform infrared spectra indicated that the absorption bands were blue-shifted with increasing Co concentration. The UV–visible absorption spectra showed high absorption in the UV region and weak absorption in the visible region. An increase in the energy band gap for the maximum absorption peak was observed from 3.49 eV for ZnO to 3.88 eV for Zn0.91Cu0.04Co0.05O. The Burstein–Moss effect explained the noticed blue shift in absorption spectra and energy band gaps. The vibrating sample magnetometer study revealed the change in the diamagnetic behavior of pure ZnO to the ferromagnetic behavior of the prepared nanoparticles at room temperature for different doping concentrations. In the current study, we have developed the room-temperature ferromagnetism (RTFM) for Cu and Co co-doped ZnO nanoparticles. Since RTFM is the key objective for dilute magnetic semiconductors, therefore it can be served as the desirable expectant for spintronics applications with improved functionalities and device concepts.

CoNiZn and CoNiFe Nanoparticles: Synthesis, Physical Characterization, and In Vitro Cytotoxicity Evaluations

The polyol method has been used to synthesize CoNiFe and CoNiZn alloy nanoparticles (NPs). The magnetic characteristics of the products have been measured by vibration sample magnetometry (VSM) analysis. At the same time, the microstructure and morphology were inspected by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Magnetic measurement of samples by the VSM indicated that samples have soft ferromagnetic behavior. Spherical-shaped grains for samples were confirmed by the SEM. MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and lactate dehydrogenase (LDH) assays were used to determine the cytotoxic effects of the synthesized NPs. Cytotoxic evaluations showed that treatment with 25 to 400 µg/mL of CoNiZn and CoNiFe NPs exerted a significant time- and concentration-dependent toxicity in MCF7 and HUVEC cells and markedly enhanced the LDH leakage after 48 h of exposure (p < 0.05 compared with untreated cells). Furthermore, NPs with concentrations higher than 12.5 µg/mL induced evident morphological changes in the studied cell lines. Treatment with 12.5 µg/mL of CoNiZn and CoNiFe NPs was safe and did not affect normal human cell survival. The results of in vitro cytotoxicity assessments show promise in supporting the suitability of the synthesized NPs to build high-performance theranostic nanoplatforms for simultaneous cancer imaging and therapy without affecting normal human cells.

The modified magnetodielectric response in KNN-CZFMO based particulate multiferroic composite system

Lead-free multiferroic composites of 1[Formula: see text](K[Formula: see text]Na[Formula: see text]NbO[Formula: see text](Co[Formula: see text]Zn[Formula: see text](Fe[Formula: see text]Mn[Formula: see text]O4 (KNN-CZFMO), where [Formula: see text]= 0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1.0, have been investigated for their structural, morphological, electrical, magnetic, dielectric and magneto-dielectric properties. Presence of KNN and CZFMO crystal structure in each composite has been confirmed from X-ray diffraction analysis (XRD). Cuboidal-shaped grains of KNN and spherical-shaped grains of CZFMO have been observed by scanning electron microscopy (SEM). The room temperature ferroelectric behavior as confirmed by polarization versus electric field ([Formula: see text]–[Formula: see text] hysteresis loops has been found to be decreasing with increasing CZFMO concentration. Increasing magnetic ordering with the increase in CZFMO concentration in the prepared composites has been observed by magnetization versus magnetic field ([Formula: see text]–[Formula: see text] hysteresis loops. The electrical conductivity of composites has been studied using Jonscher’s universal power law. The room temperature dielectric constant ([Formula: see text] and dielectric loss (tan [Formula: see text] have been observed to decrease with the increase in the frequency of the applied external electric field. The dielectric relaxation behavior has been observed using curve fitting analysis via the Havriliak–Negami relaxation model. Maximum value of the magnetodielectric (MD) effect [Formula: see text]−11% at a frequency of 1 kHz with the applied magnetic field of 1 T has been achieved for 0.9 KNN−0.1 CZFMO ([Formula: see text]= 0.1) composite in the present research work.

Analysis of different annealing conditions on physical properties of Bi doped CdTe thin films for potential absorber layer in solar cells

The mainstream technology used for production of high-efficiency CdTe photovoltaics involves Cu doping to CdTe absorber and CdTe/CdS junction activation by cadmium chloride (CdCl2), however, both procedures restrict their use for long term operation. With purpose of seek alternatives, herein, air and MgCl2 annealing along with CdCl2 is performed over e-beam evaporated CdTe:Bi films for their role in absorber photovoltaics. Structural properties indicate appearance of cubic (1 1 1) preferred peak where grain size is found to be affected with nature and temperature of annealing. Optical properties divulge variation in absorbance with annealing, also direct energy band gap is estimated in 1.42–1.69 eV range. All investigated films demonstrated ohmic behavior where conductivity is affected by Bi dopant. Surface morphological properties demonstrated uniform deposition with spherical-shaped grains for pristine as well as 150 °C and 300 °C air annealed films which changed to polyhedral at further annealing. Appeared Cd and Te peaks in EDS patterns validated CdTe films deposition. Surface topographical properties display ditch and dike structures for pristine and 150 °C annealing and hillock structures for higher annealing. Thus, present study imparts critical insights to air, CdCl2 and MgCl2 annealing effect on properties to CdTe:Bi films and designate that chloride treatment is less-effective during Bi doping to CdTe.

Influence of sprayed nanocrystalline Zn-doped TiO2 photoelectrode with the dye extracted from Hibiscus Surattensis as sensitizer in dye-sensitized solar cell

Highly oriented Zn doped TiO2 thin films (0, 2, 4, 6 and 8at%) were deposited by spray pyrolysis technique. X-ray diffraction analysis showed a strong orientation along (101) direction for 6at% Zn with polycrystalline tetragonal anatase phase. Scanning electron microscopy observations revealed uniform distribution of spherical-shaped grains, whereas columnar arrangement of tetragonal-shaped grains with porous nature was revealed from atomic force microscopy. Transmittance spectra indicated a decrease in the energy band gap with increasing doping concentration; i.e. 3.55 up to 3.21eV, attributed to grain refinement to the nanoscale regime. The optical constants such as refractive index and extinction coefficient as a function of wavelength, were determined; the low extinction coefficient values confirmed the good quality of the thin films. Photoluminescence spectra showed strong emissions at 423 and 437nm with a weak emission at 505nm, which confirmed the lesser defect density in 6at% Zn film. The electrical properties studied by Hall Effect measurements revealed that the 6at% Zn led to an increase in the carrier concentration, as well as an increase in the mobility with a least resistivity. The efficiency of dye sensitized solar cells, assembled by using natural dye extracted from Hibiscus Surattensis as sensitizer and Zn-doped TiO2 nanocrystalline thin films as a photoelectrode, was found to be around 1.22%.

Comparison studies on electrodeposited CdSe, SnSe and Cd x Sn1−x Se thin films

Electroplated cadmium stannous selenide (Cd x Sn1−x Se) thin films were coated on indium-doped tin oxide (ITO) conducting glass substrates from aqueous bath solutions containing CdCl2, SnCl2, and Na2SeO3. The x value was tuned by change in metal ion source concentration of the electrolytic bath solution. The various x values such as 1, 0.7, 0.45, and 0, of Cd x Sn1−x Se thin films were characterized by structural, morphological, compositional, and optical properties using X-ray diffraction, scanning electron microscopy, energy dispersive analysis by X-rays, and UV-vis-NIR spectrophotometer, respectively. X-ray diffraction (XRD) patterns revealed that the deposited films exhibit polycrystalline nature Cd x Sn1−x Se thin films. The microstructural parameters such as crystallite size, dislocation density, microstrain, and number of crystallites per unit area were calculated and presented. Morphological studies revealed that spherical-shaped grains were observed in cadmium-dominated films and nano-rod-shaped grains were observed in tin-dominated films. Optical properties of CdSnSe films were determined from optical transmittance data in the spectral range 400 to 1,100 nm. The optical direct transition energy band gap was estimated using conventional method, and band gap energy was lying between 1.02 and 1.83 eV. The refractive index, extinction coefficient, and real and imaginary parts of dielectric constants were calculated using optical transmission spectra of Cd x Sn1−x Se thin films.

Investigation of the structural, optical and dielectric properties of highly (100)-oriented (Pb0.60Ca0.20Sr0.20)TiO3 thin films on LaNiO3 bottom electrode

Highly (1 0 0)-oriented Pb0.60Ca0.20Sr0.20TiO3/LNO/LAO structure was fabricated using a chemical deposition process via spin-coating technique. XRD revealed that both LNO and Pb0.60Ca0.20Sr0.20TiO3 films grown on LAO(1 0 0) substrate and LNO/LAO(1 0 0) structure were crystallized to be highly (h 0 0)-oriented, respectively. AFM images revealed smooth surfaces, spherical-shaped grains and a crack-free surface with a roughness of about 3–7 nm. The tetragonal perovskite phase was confirmed by Raman spectroscopy for Pb0.60Ca0.20Sr0.20TiO3/LNO/LAO and Pb0.60Ca0.20Sr0.20TiO3/LAO structures. The optical transmittance of 340 nm thick Pb0.60Ca0.20Sr0.20TiO3 films on a LAO(1 0 0) substrate exhibited an average transmittance above 80% in the wavelength range of 500–1000 nm and an optical band gap Eg of 3.56 and 2.87 eV for the direct and indirect transition processes, respectively. The Au/Pb0.60Ca0.20Sr0.20TiO3/LNO/LAO structure has a hysteresis loop with remnant polarization, Pr, of 12 μC/cm2, and a coercive field, Ec, of 46 kV/cm for an electric field at 370 kV/cm along with a dielectric constant over 1200.

Experimental Investigation of Spray-Deposited Fe-Doped ZnO Nanoparticle Thin Films: Structural, Microstructural, and Optical Properties

Structural, microstructural, and optical properties of the undoped and Fe-doped zinc oxide (ZnO) thin films grown by spray pyrolysis technique using zinc nitrate as a host precursor have been reported here. X-ray diffraction spectra confirm that all the films have stable wurtzite structure and the effects of Fe dopants on the diffraction patterns have been found to be in agreement with the Vegard’s law. Scanning electron microscopy results show good uniformity and dense surface having spherical-shaped grains. Energy dispersive x-ray analyses with elemental mapping of the Fe-doped films show that the Fe dopants are incorporated homogeneously into the ZnO film matrix. The x-ray photoelectron spectroscopy spectra confirm the presence of 3+ oxidation state of Fe in the doped films. Atomic force microscopy analyses clearly show that the average surface roughness and the grain size decrease with the addition of Fe dopants. Optical studies reveal that the optical band gap value decreases on Fe doping. The 1 at.% Fe-doped film shows normal dispersion for the wavelength range 450-700 nm. The PL spectra of the films show a strong ultraviolet emission centered at ~388 nm in the case of 1 at.% Fe-doped film. A slow photo current response in the films has been observed in the transient photoconductivity measurement.

Alcohol-sensing characteristics of spray deposited ZnO nano-particle thin films

ZnO nano-particle thin films were deposited on cleaned glass substrates by spray pyrolysis technique using the precursor solution of zinc acetate dihydrate [Zn(CH 3COO) 2·2H 2O]. Structural analyses and surface morphology of the resulting films were carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analyses confirm that the films are polycrystalline zinc oxide, possessing hexagonal wurtzite structure with crystallite size ∼25 nm. The SEM micrograph of the film shows a good uniformity and a dense surface having spherical-shaped grains. Alcohol sensing characteristics of the deposited films have been investigated for various concentrations of methanol, ethanol and propan-2-ol in air at different operating temperatures. At 150 ppm concentration, the film shows maximum response (85.2%) to propan-2-ol at the operating temperature of 250 °C; whereas at the same concentration 150 ppm, the maximum responses to methanol and ethanol at 300 °C are observed to be 75.8% and 52.4%, respectively. Also, the film exhibits selective high response to propan-2-ol, followed by ethanol and methanol, respectively at each operating temperature up to 275 °C. This selectivity is more pronounced in the region of lower operating temperatures and concentrations. A possible reaction mechanism of alcohol sensing has been proposed.

Monte Carlo simulation on the electron beam incident angle with spherical particles applied to the energy loss in ZnS phosphor powders

During electron beam irradiation of ZnS phosphor powders, a non-luminescent ZnO layer is formed on the powder due to electron-beam-stimulated surface reactions. As the thickness of the oxide layer increases, the energy loss in the ZnS bulk decreases with a subsequent degradation in cathodoluminescence (CL). Owing to the morphology of the phosphor powder, growth of the oxide layer leads to varying effective ZnO thicknesses. In this paper the effect of the interaction between the electron beam and the ZnO/ZnS powder particles on the energy loss in the ZnS is studied using Monte Carlo simulation techniques. In the simulation, an electron beam with a certain profile is spread according to a Gaussian distribution function over the phosphor particles. These particles consists of both flat and spherical-shaped grains. The incident angle between the electron beam and the particle's surface is determined by using simple vector analysis. If the beam contains a sufficient number of electrons, a distribution of incident angles can be obtained. It was found that this distribution is independent upon the profile of the electron beam as long as the full width at half-maximum (FWHM) beam diameter is larger than the size of the irradiated particles. Using these results a comparison was made between the energy loss in the ZnS particles as a function of the ZnO thickness with and without the angular distribution. A publicly available Monte Carlo code for electron trajectory simulations in solids, called CASINO, was used for this purpose. When the distribution is considered, there is a decreased energy loss in the ZnS bulk. Because the light generation during electron beam irradiation is proportional to this energy loss, the morphology of the phosphor powder also contributes to the CL degradation. Copyright © 2000 John Wiley & Sons, Ltd.