Optical Band Gap Of Samples Research Articles

Synthesis, characterization and bioactivity of thio-acetamide modified ZnO nanoparticles embedded in zinc acetate matrix

ZnO nanoparticles embedded in zinc acetate matrix were synthesized by chemical route. The effect of thio-acetamide concentration during its synthesis was probed by structural, morphological, optical and bioactivity studies. XRD characterization indicated the formation of dominant phase of zinc acetate along with the low intensity peak of wurtzite ZnO. Morphological transition from bulky-like feature to flower-like feature via flake-like feature, is evidenced with increasing thio-acetamide molar concentrations. The optical band gap of samples decreased from ∼3.29 to 3.24 eV whereas the emitted color shifted from near green to blue region with increasing of molar concentration of thio-acetamide from 0 to 30% in the sample. The nanoparticles exhibited antimicrobial activity against seven (7) common human pathogenic bacteria including drug resistant varieties K. pneumonaie and S. aureus. The nanoparticles formed pores in the biological model membranes made from egg-phosphatidyl choline. Our study reveals that the thio-acetamide modified ZnO nanoparticles embedded in zinc acetate matrix could be used as potential drug lead to fight drug resistance against K. pneumoniae and S. aureus.

Effect of Mn-doping on the optical and electronics characteristics of cadmium sulfide photocatalyst prepared under different conditions

CdS and Cd0.95Mn0.05S were synthesized using a thermolysis procedure in the air and underflow of nitrogen. Rietveld analysis for X-ray diffraction data revealed that all samples have two phases (hexagonal wurtzite and cubic zinc blende). The effect of Mn doping and the preparation conditions on the phase percentages, the crystallite size, lattice parameters and vibrational bands were investigated in detail. The optical band gap of CdS reduced when formed in N2 compared with sample formed in air. Upon doping with Mn, the optical band gap of samples (in air or nitrogen) exhibited a redshift. Density function theory calculation (DFT) revealed a semiconductor feature with a direct band gap for all samples except Mn-doped CdS with cadmium deficiency; it has a half metallic nature. DFT calculations manifested that for the Mn-doped samples, the optical conductivity was enhanced in the visible range considering sulfur deficiency, while considering Cd deficiency the sample has an optical conductivity response only in the IR region. The calculations were performed to examine the influence of Mn doping on the structure, optical, magnetic and electronic characteristics of CdS (stoichiometric and non- stoichiometric).

Physical properties and enhanced photocatalytic activity of ZnO-rGO nanocomposites

Both zinc oxide (ZnO) and reduced graphene oxide (rGO) are known for its attractive optical properties in their nano form. Here, ZnO-rGO nanocomposites and rGO were prepared via simple and reproducible hydrothermal as well as modified Hummer’s method. Microstructural identification of phase formation and dispersion of ZnO on rGO was confirmed by X-ray diffraction and transmission electron microscopy (TEM) measurements. The reduction of graphene oxide was confirmed by the appearance of D and G band peaks in Raman spectra. Optical bandgap of samples was estimated by UV–Visible diffused reflectance spectroscopy up to IR region. A systematic study of photocatalytic behavior towards the degradation of organic dyes such as methyl orange and rhodamine B under the influence of UV light source is demonstrated. Better than 85% of degradation was measured for both the dyes in the presence of ZnO-rGO composite during 2 h of UV illuminations. The enhanced photocatalytic activity of the composites is attributed to electron–hole charge transfer, which also promises its use in photovoltaics.

Investigation of structural, optical, and magnetic properties of Nd‐doped Sr2SnO4 Ruddlesden Popper oxide

AbstractThe samples of Sr2‐xNdxSnO4 with x = 0, 0.01, 0.02, 0.04, 0.06, and 0.10 were synthesized by a high‐temperature solid‐state ceramic route. Rietveld refining of X‐ray diffraction results showed that all the synthesized compositions are single phase under tetragonal crystal structure. The presence of functional group and local structure has been studied using FTIR and Raman spectroscopy, respectively. XPS study of samples showed the presence of oxygen vacancy and interstitial oxygen in the sample. Optical band gap of samples analyzed by UV‐Vis spectra gradually increases with dopant concentration, and Photoluminescence (PL) spectroscopy study showed most intense emission around 1064 nm. Room‐temperature magnetic hysteresis curve in sample SSN2 showed ferromagnetism, slowly decreasing with Nd and becoming antiferromagnetic for higher compositions. Utilizing the absorption state observed in PL as metastable state makes it promising candidate for laser and IR detector application and the ferromagnetic/antiferromagnetic nature of sample makes it suitable candidate for spintronics device applications.

Ascendancy of iron ions on lithium ion conductivity, optical band gap, Urbach energy and topology of LiF-SrO-B2O3 glasses

The transparent glass network 30LiF-10SrO-(60-x)B2O3-xFe2O3, is synthesized by melting quench technique, with 0 ≤ x ≤ 5 mol% (x = 0, 1, 2, 3, 4 and 5). These glasses are analyzed by X-ray diffraction (XRD), optical absorption, electron spin resonance (ESR), Fourier transform infrared (FTIR) studies and dielectric properties. Optical absorption spectra demonstrate a band at 446 nm corresponding to Fe3+ ions. Optical band gap of samples decreases with an increase in dopant. The intensity of ESR signal, at g ≈ 4 owing to rhombically distorted octahedral (FeO6) Fe3+ ions is raised up to 3 mol% of dopant and decreased at higher concentrations. FTIR displayed the conventional borate groups. A gradual increase is perceived in the dielectric variables like dielectric constant, ε′, dielectric loss, Tanδ, and a.c. conductivity, σac, with an increase in content of Fe2O3. All results suggest the gradual increase in semiconducting nature of glasses.

Structural, optical, magnetic and photoelectrochemical properties of (BiFeO3)1−x(Fe3O4)x nanocomposites

(BiFeO3)1−x(Fe3O4)x nanocomposites were prepared by dispersion of Fe3O4 nanoparticles (NP) into sol–gel synthesised BiFeO3 (BFO) matrix followed by calcination at 500 °C. Samples with x = 0.0, 0.2, 0.33 and 0.5 were investigated using X-ray diffractions (XRD), UV–vis spectroscopy, photoluminescence spectroscopy (PL), transmissions electron microscopes (TEM), electron spin resonance (ESR), vibrating sample magnetometer (VSM) and photoelectrochemical (PEC) measurements. Formation of nanocomposites was confirmed by XRD and TEM. The XRD patterns showed presence of both BFO and Fe3O4 phases without any secondary phases. The crystallite size of BFO (39.1–51.1 nm) is much bigger than that of Fe3O4 (10.1–12 nm). Microstrain of BFO decreased for sample x = 0.2 and 0.33 and then increased for x = 0.5. Optical band gap of samples decreased from 2.5 eV for x = 0.0–1.96 eV for sample x = 0.5. The PL emission which centred at 428.1 eV for x = 0.0 increased gradually for samples x = 0.2 and 0.33 and then decreased for x = 0.5. Exchange bias (HEB) was observed for hysteresis loops of all samples, and the highest value of HEB was 38.4 Oe for x = 0.5. The g-values of the nanocomposites, ranged between 2.23 and 2.20, were higher than that of the BFO and Fe3O4 components. The PEC measurement showed the photocurrent density increased with x. Finally, modulations of the physical properties of BFO/Fe3O4 system were analysed and discussed in detail.

Spin coated multilayered CuO/ZnO films with high output power under irradiation

Thin films of pure CuO, pure ZnO and CuO/ZnO multilayers were synthesized using the spin coating technique. CuO and ZnO layers were spin coated for 30 s at speeds of 2000 and 1500 rpm, respectively. All the samples were subsequently annealed at 500 °C for one hour in air. Structural properties of films investigated using XRD patterns indicated the crystallization of single phase of CuO and ZnO. Optical band gaps of samples determined by UV-Visible spectrums were in the range of the band gaps of CuO and ZnO. The main objective of the preparation of multilayered CuO/ZnO was enhancing the output power by combining wide band gap and narrow band gap materials. CuO with higher photocurrent and ZnO with higher photovoltage were employed to achieve this task. Photocurrent, photovoltage and impedance were measured in order to investigate the electrical properties of these samples. A liquid junction photocell with electrolyte potassium iodide (KI) was employed to measure photovoltaic properties. A multilayer with ZnO as the top layer provides a higher output power of 3.6 μW cm−2 compared to the output power of a multilayer with CuO as the top layer (1.1 μW cm−2). This is the highest output power reported for a multilayer of CuO/ZnO without any dye coating in KI electrolyte. The highest output power of our multilayered samples is more than twice the previously reported highest output powers of pure CuO and pure ZnO thin film samples without dye coating. Chemical properties of samples were confirmed by FTIR. Crystallite sizes were in the range from 23 to 28 nm. Impedance curves of the samples were measured under dark and light conditions. Two semicircles could be observed at Nyquist plots of both multilayer samples.

Characterization studies of the structure and properties of Zr-doped SnO2 thin films by spin-coating technique

Transparent electrodes made of transparent conductive oxides materials are widely used in optoelectronic devices. The zirconium doped tin oxide films as transparent conductive oxides were prepared by spin-coating technique. The morphology, structure, optical properties and electrical properties of the tin oxide thin films were investigated as a function of zirconium doping concentration. The results show that the films crystallize with a tetragonal rutile structure. And the surfaces of all the films are free of cracks. The average transmittance of the tin oxide films can be reached up to 96% in the visible region by incorporating zirconium, and the optical band gap of samples varies from 3.88 eV to 3.95 eV with the increasing zirconium doping concentration. The tin oxide films with 1 at.% zirconium doping show the lowest resistivity (2.91 × 10−2 Ω cm) and high carrier concentration (4.39 × 1019 cm−3) with mobility (4.90 cm2/V) via Hall effect measurement system.

Role of Cu in engineering the optical properties of SnO2 nanostructures: Structural, morphological and spectroscopic studies

We have carried out a systematic study to investigate the effect of Cu doping on the optical properties of SnO2 nanostructures synthesized by chemical route. Synthesized nanostructures were characterized using X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), High resolution transmission electron microscopy (HR-TEM), Energy dispersive X-ray spectroscopy, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, UV–visible and Photoluminescence (PL) spectroscopy. The Rietveld refinement analysis of XRD patterns of Cu-doped SnO2 samples confirmed the formation of single phase tetragonal rutile structure, however some localized distortion was observed for 5 mol% Cu-doped SnO2. Crystallite size was found to decrease with increase in dopant concentration. FE-SEM images indicated change in morphology of samples with doping. HR-TEM images revealed that synthesized nanostructures were nearly spherical and average crystallite size was in the range 12–21 nm. Structural defects, crystallinity and size effects on doping were investigated by Raman spectroscopy and results were complemented by FTIR spectroscopy. Optical band gap of samples was estimated from reflectance spectra. We have shown that band gap of SnO2 can be engineered from 3.62 to 3.82 eV by Cu doping. PL emission intensity increased as the doping concentration increased, which can be attributed to the development of defect states in the forbidden transition region of band gap of SnO2 with doping. We have also proposed a band model owing to defect states in SnO2 to explain the observed PL in Cu doped SnO2 nanostructures.

Structural and optical properties of Cu2ZnSnS4 synthesized by ultrasonic assisted sol-gel method

Cu2ZnSnS4 (CZTS) nanocrystals were synthesized by a simple ultrasonic assisted sol-gel method using two different solvents. Structure and purity of the phase formed were investigated using X-ray diffraction (XRD) and Raman measurements. The average crystallite size were estimated by using Scherrer's formula and found to be 2.09 and 7.15 nm. Raman study reveals the kesterite-phase of prepared samples. The influence of solvent in the morphologies of prepared samples was investigated by field emission scanning electron microscopy (FESEM). Ultraviolet–visible–near-infrared absorption measurement was carried out to calculate the optical band gap of samples. Oxidation state of the constitute elements of as-prepared samples were investigated by X-ray photoelectron spectroscopy (XPS) analysis and the results are in good agreement with the literature. The surface area and pore volume were estimated after analysis of nitrogen adsorption-desorption isotherm curves and found to be 16.5 m2/gm and 0.01 cm3/gm respectively.

HIGH-k GATE DIELECTRIC: AMORPHOUS Ta/La2O3 FILMS GROWN ON Si AT LOW PRESSURE

In the present study, Ta / La 2 O 3 films ( La 2 O 3 doped with Ta 2 O 5) as a gate dielectric were prepared using a sol–gel method at low pressure. Ta / La 2 O 3 film has some hopeful properties as a gate dielectric of logic device. The structure and morphology of Ta / La 2 O 3 films were studied using X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Electrical properties of films were performed using capacitance–voltage (C–V) and current density-voltage (J–V) measurements. The optical bandgap of samples was studied by UV-visible optical absorbance measurement. The optical bandgap, E opt , is determined from the absorbance spectra. The obtained results show that Ta / La 2 O 3 film as a good gate dielectric has amorphous structure, good thermal stability, high dielectric constant (≈ 25), low leakage current and wide bandgap (≈ 4.7 eV).

Effect of pyrolysis temperature on the electrical, optical, structural, and morphological properties of ITO thin films prepared by a sol–gel spin coating process

Tin doped indium oxide (ITO) thin films were fabricated by sol–gel spin coating (S–G-S) method with In(NO3)3·H2O and SnCl4 as indium and tin precursors, respectively. Polyvinylalcohol (PVA) was used for synthesis of ITO sol as a stabilizer and binder. The influence of different pyrolysis temperatures after each coating on the electrical, optical, structural, and morphological properties of the films were characterized by means of four point probe, UV–Vis, FT-IR spectroscopy, X-ray diffraction and scanning electron microscopy (SEM). Then the prepared thin films were annealed in the temperature of 550°C under argon atmosphere (the rate of 100mL/min and the pressure of 10Torr). The obtained results indicate that minimum resistivity of 12.5×10−4Ωcm and optical transmittance of more than 83% in the UV–Vis region with a band gap of 3.84eV were achieved for the films pyrolyzed at 500°C for 30min. X-ray diffraction analysis confirmed the formation of cubic bixbyite structure of indium oxide by the main peak of the (222) plane. The grain size of ITO nanoparticles was obtained about 25–50nm and the thickness of the film was investigated by SEM surface images and cross-section images, respectively and the effect of Burstein-Moss on optical band gap of sample was discussed too.

Humidity sensing characteristics of Sn doped Zinc oxide based quartz crystal microbalance sensors

The electrical, optical and humidity sensor properties of nanostructured ZnO samples were investigated. The structural properties of Sn doped ZnO samples were characterized by X-ray diffraction and atomic force microscopy. It was found that the all samples have a hexagonal crystal structure. The electrical conductivity of the samples indicates that undoped and Sn doped ZnO samples exhibit the semiconducting behavior. The optical absorption method was used to determine the optical band gaps of the samples. The optical band gap and activation energy values of the ZnO samples were changed with Sn doping. The ZnO based on quartz crystal microbalance humidity sensors were prepared and sensing properties of the sensors were changed with Sn doping. The response time required to reach 70 % is about 13–16 s, while the recovery time from 70 to 30 % RH is about 13–15 s. The fast response of the sensors is due to easy diffusion of water molecules between ZnO nanopowders. The prepared sensors have a high reproducibility and sensitivity for humidity sensing applications.

Enhanced Absorption and Raman Scattering Signal in Cu<sub>2</sub>ZnSnS<sub>4</sub> Film through Excitation of Surface Plasmon Polaritons

We deposited silver on the surface of Cu2ZnSnS4 (CZTS) thin films by vacuum evaporation and then annealed it under vacuum condition. The surface-enhanced Raman scattering (SERS) is revealed by comparing Raman spectra of CZTS and CZTS-Ag films. The enhancement of the optical absorption is observed via investigating transmission spectrum. It is found that the CZTS-Ag film display a low transmittance, namely high absorption. Furthermore, X-ray diffraction and the optical band gap of samples show the pure CZTS phase with high crystal quality. The CZTS compound in CZTS-Ag films grow well and is not influenced by Ag nanoparticles.

Preparation of New Structural TiO<sub>2</sub> Nanotube Arrays and Study of Photoelectric Properties

NH4F with ethylene glycol solution as the electrolyte, the anodic oxidation of titanium mesh surface in preparation of ordered TiO2 nanotube array. The structure, morphology and absorption properties of samples were characterized by XRD, SEM and UV spectrophotometer. The results show that, in a certain time range, nanotube length and diameter will increase with the increase of oxidation time. The best oxidation time is 60min. Ultraviolet visible spectrophotometer results show that, the optical band gap of samples is from 3.26-3.42eV. The photoelectric conversion characteristics of dye sensitized solar cell assembled with prepared nanotube arrays were tested.

ITO substrate resistivity effect on the properties of CuInSe2 deposited using two-electrode system

The purpose of this work is to deposit the CuInSe2 films on the ITO substrate by electrodeposition technique using a simplified two electrodes system and to investigate the effect of ITO sheet resistance on the fundamental properties of the resulting films. The as deposited films were annealed under argon atmosphere at 300 °C during 30 min. The structural, morphological and electrical properties were characterized respectively by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrical resistivity measurements. The optical band gap of samples was estimated using the optical absorption technique. After annealing, the XRD spectra show diffraction peaks corresponding to the single-phase chalcopyrite CuInSe2 with (112) as main reflection. The SEM images reveal a homogeneous surface and the estimated grain size was calculated from Scherrer’s Equation with (112) peak lay in the range of 165–272 A. The band gap, Eg, is a decreasing function with the ITO sheet resistance.

Structural, electrical and optical properties of Ge implanted GaSe single crystals grown by Bridgman technique

AbstractStructural, optical and electrical properties of Ge implanted GaSe single crystal have been studied by means of X‐Ray Diffraction (XRD), temperature dependent conductivity and photoconductivity (PC) measurements for different annealing temperatures. It was observed that upon implanting GaSe with Ge and applying annealing process, the resistivity is reduced from 2.1 × 109 to 6.5 × 105 Ω‐cm. From the temperature dependent conductivities, the activation energies have been found to be 4, 34, and 314 meV for as‐grown, 36 and 472 meV for as‐implanted and 39 and 647 meV for implanted and annealed GaSe single crystals at 500°C. Calculated activation energies from the conductivity measurements indicated that the transport mechanisms are dominated by thermal excitation at different temperature intervals in the implanted and unimplanted samples. By measuring photoconductivity (PC) measurement as a function of temperature and illumination intensity, the relation between photocurrent (IPC) and illumination intensity (Φ) was studied and it was observed that the relation obeys the power law, IPC αΦn with n between 1 and 2, which is indication of behaving as a supralinear character and existing continuous distribution of localized states in the band gap. As a result of transmission measurements, it was observed that there is almost no considerable change in optical band gap of samples with increasing annealing temperatures for as‐grown GaSe; however, a slight shift of optical band gap toward higher energies for Ge‐implanted sample was observed with increasing annealing temperatures. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of annealing temperature on phase transition and optical property of titanate nanotubes prepared by ion exchange approach

In this paper, the effect of the annealing temperature on the phase transition and optical property of titanate nanotubes was discussed in detail. TGA results indicated that the dehydration process happened when titanate nanotubes were annealed. Up to 450 °C, the weight loss ceased entirely. XRD results showed that anatase and triclinic Ti 5O 9 were formed in annealed samples. TEM was used to observe the micrographs of samples. SAED patterns indicated that the granular phase and the rod-shaped crystal were triclinic Ti 5O 9 and anatase, respectively. In addition, UV–vis diffuse reflectance spectra were used to study the optical band gap of samples annealed at different temperature.

Electrical conductivity and optical properties of copolymers based on 4-vinylpyridine and tetralincyclobutylhydroxyethylmethacrylate

The electrical conductivity and the optical absorption of the 4-vinylpyridine and amorphous tetralincyclobutylhydroxyethylmethacrylate poly(TCHEMA–co-4VP) copolymers, which were prepared with three different compositions by using polymerization technique, were studied and the obtained results were analyzed. The conduction mechanisms of samples were determined via DC and AC electrical conductivity measurements. The DC plots of samples suggested that there were two types of conduction channels contributing to conductivity. Their electrical conductivities were found in range 10 −9 to 10 −8 S/cm at room temperature. Also, the dependence of AC conductivity to frequency was detected as ω 0.91–0.96. The optical band gaps of samples were determined by means of optical absorption spectra and found as 1.79, 3.27 and 3.14 eV for PVP60, PVP70 and PVP80, respectively.

The influence of the growth conditions on the structural and optical properties of hydrogenated amorphous silicon carbide thin films

Two series of hydrogenated amorphous silicon carbide (a-SiC:H) films have been prepared by using plasma-enhanced chemical-vapor deposition (PECVD) with the gas mixture of methane (CH4) and silane (SiH4). The influence of the r.f. power density on the structural and optical properties of the films has been investigated with the CH4 gas ratio in the total gas flow rate ranging from 50 to 90%. The r.f. power density is an important parameter which affects both the carbon content and the structures of the films. Under high r.f. power condition, the samples are Si-rich and the structure of them is described as a disordered amorphous silicon network in which hydrogen atoms are incorporated in the form of Si–CH2 and Si–CH3 entities and carbon atoms are in a sp3 carbon-related configuration. The optical band gaps of these samples increase with the increase of the gas flow ratio. Under low r.f. power condition, the samples are carbon-rich and the structure of them is a mixed phase of amorphous Si and graphite-like C clusters. The optical band gap of the series samples decrease with the increase of the gas flow ratio.