Optical Properties Of Zn1 Research Articles

Effect of Sintering Temperature on Zn0.94Cr0.03Fe0.03O Nanostructures

In present work, we report structural, morphological and optical properties of Zn0.94Cr0.03Fe0.03O nanostructures synthesized by hydrothermal method. The as prepared Zn0.94Cr0.03Fe0.03O samples were sintered in air at different temperatures (RT- 400 0C) to understand the effect of sintering temperature on the structural, morphological and optical properties of Zn0.94Cr0.03Fe0.03O nanostructures. The samples are characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) and UV-visible spectroscopy. The XRD patterns show a pure phase corresponding to ZnO without any other phases, indicating that Cr and Fe atoms are successfully doped into the lattice of ZnO. Moreover, PL spectrum also confirms the wurtzite phase formation of ZnO. Furthermore, the optical band gaps calculated through UV-visible spectroscopy is found to be decreasing as increasing the sintering temperature.

Effect of pH variation on structural and optical properties of Zn0.95Co0.05O nanoparticles

We have synthesized the Zn0.95Co0.05O nanoparticles using a sol–gel method with different pH values under acid base and basic base reactions. The structural properties were characterized using powder X-ray diffraction (XRD) and scanning electron microscope (SEM) while the optical properties were characterized using Ultraviolet/Visible (UV/Vis) spectroscopy, Fourier transform infra red (FTIR) spectroscopy and Raman spectroscopy. Both samples are found in single phase with wurtzite structure. SEM micrographs show spherical nanoparticles for the sample synthesized under acid base reaction (pH=6) and nanorods for the sample synthesized under basic base reaction (pH=9). The band gap estimated using UV/Vis spectra shows an increase with the increase in pH value. FTIR spectra show that typical stretching mode peak of ZnO at 497cm−1. On Co doping this absorption peak shifted to 446cm−1 (for pH=6 sample) and to 478cm−1 (for pH=9 sample). Raman spectra of cobalt doped samples reveal presence of small amounts of ZnCo2O4 and Co3O4. Fluorescence spectra display blue shift in near band emission peak of ZnO with cobalt doping and pH variation.

Investigation of optical properties of Zn1-xVxO (x = 0.0, 0.125, 0.25, 0.5) by first principles calculations

In this paper, some optical properties of Zn 1-x V x O (0 ≤ x ≤ 0.5) such as real and imaginary part of dielectric function, energy loss function, plasmon energies and refractive index are investigated by first principles calculations. The calculations were performed in density functional theory (DFT) framework using full potential linear augmented plane wave (FP-LAPW) and generalized gradient approximation (GGA). Analysis of dielectric function shows that by substituting V instead of Zn in Zn 1-x V x O , static dielectric function, absorption and anisotropy at low energies are increased. The investigations show that V doping in ZnO affects plasmon energies. The plasmon energies have been compared with free electron model. The calculated plasmon energy for pure ZnO is nearly close to other works. The refractive index at low energies is increased significantly, so that V -doped ZnO can be used as a high refractive material.

First principle investigations of the optical properties of Zn1-xMgxS, Zn1-xMgxSe and Zn1-xMgxTe ternary alloys

Optical properties of Zn 1-x Mg x S , Zn 1-x Mg x Se and Zn 1-x Mg x Te (0 ≤ x ≤ 1) ternary semiconductor alloys are calculated using the full potential linearized augmented plane wave within the density functional theory. The exchange correlation potential is treated by the generalized gradient approximation (GGA) within Perdew et al. scheme. The real and imaginary parts of the dielectric function ε(ω), the refractive index n(ω), the extinction coefficient k(ω), the optical absorption coefficient α(ω), the reflectivity R(ω) and the electron energy loss function (EELS) are calculated within random phase approximation (RPA). Our results are compared with the previous theoretical calculations and available experimental data. Moreover, the interband transitions responsible for the structures seen in the spectra are specified. It is shown that, the chalcogen p states as initial and Zn 4s, Mg 3s, chalcogen d states as final states perform the major role in optical transitions.

First principles study of structural, optical, and electronic properties of zinc mercury chalcogenides

First-principles calculations using the full potential linearized augmented plane wave method within the framework of density functional theory are performed to investigate the compositional dependence of the structural, electronic and optical properties of Zn1−xHgxE (E=S, Se, Te). It is observed that except the lattice constant, the variation of the bulk modulus and the band gap versus mercury composition does not obey Vegard׳s law. The alloys at all concentrations have direct band gap (Γ−Γ) which decreases with increasing the concentration of Hg. Optical properties like complex dielectric function and reflectivity are discussed comprehensively. The properties of these materials such as the direct band gap and high absorption in the infrared to ultraviolet regions demonstrate the significant optical activity of these materials.

Microstructural and optical properties of Zn(1−x)CdxO thin films grown on r-plane sapphire substrates: Effect of growth temperature and position of sample in MO-CVD reactor

In this study, the epitaxial growth of (112¯0) (≡a-plane) Zn(1−x)CdxO thin films on (011¯2) (≡r-plane) sapphire substrates was performed by metal organic chemical deposition (MOCVD) with the same cadmium flow. The influence of growth temperature (850°C≤Tg≤950°C) and position of sample in the MOCVD reactor on the microstructural and optical properties of Zn(1−x)CdxO thin films was investigated using high resolution X-ray diffraction (HRXRD), scanning electron microscopy (SEM), optical transmission measurements and photoluminescence spectroscopy (PL). A maximum Cadmium incorporation about 5.5% is obtained at Tg=850°C for the sample placed as a nearest reactor source. X-ray diffraction study revealed that all films had wurtzite phase and a-plane≡(112¯0) film are epitaxially grown on r-plane sapphire. The near band-edge photoluminescence emission shifts gradually to lower energies as Cd is incorporated and reaches 3.10eV for the highest Cd content (5.5%) at low temperature (2K). The uniform striated morphology along the [0001] ZnO direction which is a typical feature observed in non-polar ZnO is lost with an increase in the Cd incorporation content. This morphology change is due to the crystal lattice deformation which is revealed by HRXRD.

Defects induced luminescence and tuning of bandgap energy narrowing in ZnO nanoparticles doped with Li ions

Microstructural and optical properties of Zn1−yLiyO (0.00 ≤ y ≤ 0.10) nanoparticles are investigated. Li incorporation leads to substantial changes in the structural characterization. From micro-structural analysis, no secondary phases or clustering of Li was detected. Elemental maps confirmed homogeneous distribution of Li in ZnO. Sharp UV peak due to the recombination of free exciton and defects based luminescence broad visible band was observed. The transition from the conduction band to Zinc vacancy defect level in photoluminescence spectra is found at 518 ± 2.5 nm. The yellow luminescence was observed and attributed to Li related defects in doped samples. With increasing Li doping, a decrease in energy bandgap was observed in the range 3.26 ± 0.014 to 3.17 ± 0.018 eV. The bandgap narrowing behavior is explained in terms of the band tailing effect due to structural disorder, carrier-impurities, carrier-carrier, and carrier-phonon interactions. Tuning of the bandgap energy in this class of wide bandgap semiconductor is very important for room temperature spintronics applications and optical devices.

Structural, electronic and optical properties of Zn1−xZrxO nanotubes: first principles study

Structural, electronic and optical properties of Zn1−xZrxO nanotubes: first principles study

Influences of annealing temperature on structural, magnetic and optical properties of Zn0.98V0.02O nanoparticles

The Zn0.98V0.02O nanoparticles were synthesized by the sol–gel method. The relationship between the annealing temperature (600°C, 700°C and 800°C) and the structural, magnetic and optical properties of the obtained samples was studied. The results showed that Zn ions were partially substituted by V ions. The V doped ZnO nanoparticles annealed at 600°C and 700°C were single phase wurtize ZnO structure and they were ferromagnetic at room temperature. On the contrary, the sample annealed at 800°C had a secondary phase of Zn3V3O8. Therefore it was not saturated even in the field of 10,000Oe due to the coexistence of ferromagnetic and paramagnetic materials. Photoluminescence results indicated that defects probably were the origin of ferromagnetism in V doped ZnO.

Structural, morphological and optical study of Li doped ZnO thin films on Si (100) substrate deposited by pulsed laser deposition

Structural, morphological and optical properties of Zn1−xLixO thin films grown on Si (100) substrates by pulsed laser deposition at different Li doping concentrations (x=0.0, 0.05, 0.07 and 0.09) are reported. The XRD spectra indicate the formation of single crystalline ZnO thin films preferentially grown along (002) crystallographic orientation with c-axis perpendicular to the substrate surface. FESEM analysis shows the average size of Zn1−xLixO nanostructures to decrease from 42 to 30nm and AFM analysis also shows the average size of Zn1−xLixO nanostructures to decrease from 30 to 05nm with increasing lithium concentrations from x=0 to 0.09. Moreover, Raman and Photoluminescence spectra also confirm the single-phase formation of ZnO thin films. A significant enhancement in optical band gap is found from 3.35 to 3.63eV by Li doping from x=0 to 0.09. It may be due to the increased carrier concentrations by Li doping that blocks the lowest states in the conduction band and results in the increase in band gap. The obtained Zn1−xLixO thin films with c-axis oriented along (002) plane are useful for device fabrication in broadband UV photo-detectors for high tunable wavelength resolution.

First principles calculations of structural, electronic and optical properties of Zn1−xBexSeyTe1−y quaternary alloys

The structural, electronic and optical properties of Zn1−xBexSeyTe1−y quaternary alloys are investigated using the full potential-linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT). We used both the Wu–Cohen and the Engel–Vosko generalized gradient approximations of the exchange-correlation energy that are based on the optimization of the total energy and the corresponding potential, respectively. Some basic physical properties, such as lattice constant, bulk modulus, electronic band structures, and optical properties (dielectric constant and refractive index) are calculated, nonlinear dependence on the compositions x and y are found. In addition, the energy band gap of zinc-blende Zn1−xBexSeyTe1−y quaternary alloys lattice matched to GaAs substrate is investigated. To our knowledge this is the first quantitative theoretical investigation on Zn1−xBexSeyTe1−y quaternary alloys and still awaits experimental confirmations.

Zn0.94Cd0.06O nanoparticles with various structures, morphologies and optical properties toward MB optodecolorization

ZnO and Zn0.94Cd0.06O nanoparticles were synthesized by a sol–gel method at different calcination temperatures of 600, 700 and 800°C. Effect of calcination temperature on structural, morphological and optical properties of Zn0.94Cd0.06O nanoparticles was investigated by FT-IR, SEM, EDAX, XRD techniques, UV–vis absorption and photoluminescence (PL) spectroscopy. SEM micrographs showed that increase in the calcination temperature cause to change in the morphplogy of Zn0.94Cd0.06O nanoparticles from spherical at 600°C to rod-shaped particles at 800°C. XRD analysis data revealed that ZnO and Zn0.94Cd0.06O nanoparticles were crystallized in wurtzite phase. The average diameter of the synthesized nanoparticles calculated by Debbye–Scherrer formula was 29nm for ZnO and 24, 130 and 210nm for Zn0.94Cd0.06O nanoparticles calcined at 600, 700 and 800°C, respectively. UV–vis absorption and PL spectra indicated that there is a red-shift in the band-gap of Zn0.94Cd0.06O nanoparticles from 3.28eV to 3.08eV in comparison with that of pure ZnO nanoparticles and the red-shift value decreases with increase in the calcination temperature. All synthesized materials were also examined for their photocatalytic activity in decolorization of methylene blue (MB). The comparative results suggested high efficiency of Zn0.94Cd0.06O nanoparticles calcined at 600°C toward MB decolorization.

First-principles study of structural, electronic and optical properties of Zn1−xMgxO ternary alloys using modified Becke–Johnson potential

The structural, electronic and optical properties of binary ZnO, MgO and their ternary Zn1−xMgxO alloys (0≤x≤1) in zinc blende phase have been studied using the modified Becke–Johnson (mBJ) potential within the framework of density functional theory (DFT). Wu–Cohen (WC), PBE for solids (PBEsol) and Perdew–Burke–Ernzerhof (PBE) generalized gradient approximations (GGA) were also used to calculate the exchange–correlation and electronic band gap energies. The composition effect on lattice constants is analyzed. In addition, we found that the calculated band structures show that the crystal is a semiconductor with a direct band gap, and the contribution of Zn-3d and O-2p is prominent in the density of states (DOS). The dielectric function, refractive index, optical reflectivity, absorption and optical conductivity are predicted. Furthermore, the binary compound results are in agreement with existing experimental and theoretical values.

Effect of Mn-doping on the structural, morphological and optical properties of ZnO nanorods

In this study, the effect of doping concentration on the morphological, structural and optical properties of Zn1−xMnxO nanorods synthesized by solvothermal technique has been investigated. The morphological studies showed nanorod-like morphology and the preferential growth direction along the c-axis. The doping of Mn2+ ions has significant influence on the optical properties of ZnO nanorods. Room-temperature photoluminescence spectra of Mn-doped ZnO nanorods exhibit a weak emission at 381nm and a strong emission around 552nm and the spectra also indicate that the concentration of the defects increased by doping. The dynamic process of the UV absorption for Mn-doped ZnO nanorods was discussed in detail.

Study of structural and optical properties of Zn1−xAlxO nanoparticles

Al doped ZnO nanoparticles (Zn1−xAlxO, 0.00≤x≤0.05) have been synthesized by the co-precipitation method at temperature of 500°C for 2h in air. The synthesized samples were characterized by powder X-ray diffraction (XRD), FE-SEM/EDS, TEM and UV–visible spectrophotometer. The prepared nanoparticles exhibit a hexagonal wurtzite structure with an average particle size of 26nm as evident from XRD measurements. The calculated average crystalline size of particle varied from 20 to 39nm with increase in Al concentrations. The increase in lattice parameters reveals the easy fit of Al into ZnO lattice. It was observed that the Al doped ZnO nanoparticles (Zn1−xAlxO, 0.00≤x≤0.05) exhibit higher transmittance i.e. above 77% at 400nm wavelength as compared to the un-doped ZnO nanoparticles (70%) due to its smaller crystal size (23.9nm) as compared to un-doped ZnO nanoparticles (77.4nm). Also, Al doped ZnO nanoparticles showed higher optical energy band gap as compared to un-doped ZnO nanoparticles.

Nanocrystalline Zn1−x−yBexMgyO thin films synthesized by the sol–gel method: structural and near infrared photoluminescence properties

In this paper, we reports on the structural and optical properties of Zn1−x−yBexMgyO thin films prepared by sol–gel method, which are new materials for optoelectronic and ultraviolet-light-emitting devices. The crystal structure and core level spectra of these films are studied by X-ray diffraction and X-ray photoelectron spectroscopy. Surface morphology of the films is analyzed by scanning electron microscope images and the surface is composed of spherical shaped grains. Micro-photoluminescence shows a near edge band emission and the peak values tuned from 3.26 eV for the undoped to 3.4 eV for the doped ZnO film. Near infrared emission is observed in the region 1.64–1.67 eV for pure and co-doped ZnO films. In micro-Raman spectra, multiple-order Raman bands originating from ZnO-like longitudinal optical (LO) phonons are observed. A Raman shift of about 5–18 cm−1 is observed for the first-order LO phonon. A comparative study was made on Raman band for BeZnO, MgZnO and BeMgZnO nanocrystals with the LO phonon band of bulk ZnO. The ultraviolet resonant Raman excitation at room temperature shows multi-phonon LO modes up to the fourth order. Deformation energy of all the films is calculated and BeMgZnO film has the minimum deformation energy.

Antibacterial and Blue shift investigations in sol–gel synthesized CrxZn1−xO Nanostructures

In this paper, a systematic study of structural, morphological, phononic, vibrational and optical properties of Zn1−xCrxO nanostructures has been reported. These particles are synthesized through simple sol–gel chemical technique at low temperature using simply available laboratory chemicals i,e zinc acetate and sodium hydroxide. The detailed structural studies carried out by X-ray diffraction method (XRD) and transmission electron microscopy (TEM) reveals that the as-synthesized nanoparticles are well-crystalline and possessing hexagonal wurtzite structure in 54–57nm range. Scanning electron microscopy (SEM) shows the synthesized nanostrucures were grown in high density with less agglomeration and their different morphologies observed after doping. The presences of functional groups were characterized by employing Fourier transform infrared spectroscopy (FTIR). Compared with the photoluminescence (PL) spectrum of the undoped ZnO, the peak position of ultraviolet (UV) emission of the Cr-doped ZnO nanostructures exhibits remarkable blue shift, also confirmed by Raman studies, and the deep level emission band was sharply suppressed. Band gap of synthesized samples has been evaluated using DRS (UV–Vis mode). It is found that the band gap increases as Cr doping took place which is attributed to the combined effect of size reduction and doping. The synthesized CrxZn1−xO nanostructures showed potential applications in destruction of bacteria.

First-principles studies of the structural, electronic and optical properties of Zn1−xCdxS and ZnS1−ySey alloys

Using the density functional theory calculations, we studied the structural, electronic and optical properties of zincblende Zn1−xCdxS and ZnS1−ySey alloys. Calculated structures and band gaps of these alloys are in good agreement with available experimental and other theoretical values. Present results show that the prominent peaks of the dielectric functions and absorption coefficients have a slight red shift and the amplitudes become larger with the increasing concentration of Cd and Se. Moreover, present findings predict that Zn1−xCdxS and ZnS1−ySey alloys are promising for solar cells and photoconductor and electroluminescent devices due to their high absorption of solar radiations and photoconductivity in the energy region from visible light to ultraviolet.

Structural, electrical, and optical properties of Zn1−x Sn x O thin films deposited by reactive co-sputtering

Zn1−xSnxO thin films were deposited on K9 glass and Si substrates by co-sputtering Zn and Sn targets under atmospheres of Ar and O2. The samples were then characterized with X-ray diffraction (XRD), Raman, energy-dispersive X-ray spectroscopy (EDX), Seebeck effect, four-probe instrument, and UV/VIS spectrophotometry. XRD and Raman show that all the samples are hexagonal and Sn doping increases the stress greatly. EDX demonstrates that the atomic ratio of Sn to Sn plus Zn is 0.04–0.07. All the samples are n-type. The resistivity of Zn1−xSnxO is much smaller than that of undoped ZnO deposited under the same conditions. The optical bandgap of Zn1−xSnxO is also reduced compared with that of ZnO deposited under the same conditions.

Structural and optical properties of Zn–In–Te thin films deposited by thermal evaporation technique

Annealing effects on structural and optical properties of the thermally evaporated Zn–In–Te (ZIT) thin films have been investigated. The structural and the compositional analyses were carried out by means of X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDXA). The as-grown and annealed ZIT films had polycrystalline structure and the preferred orientation changed from (220) to (112) direction with increasing annealing temperature. The optical properties and constants were determined by transmittance measurements in the wavelength range of 200–2000nm. The effect of annealing on the optical parameters was determined by using Single Oscillator Model (SOM), Envelope Model (EM) and Cauchy Method. The absorbance studies revealed that the films had three distinct transitions in the high absorption region because of the tetragonal distortion, and that was used to evaluate the splitting energies of crystal-field and spin–orbit splitting. The fundamental optical band gap values were found to be lying in the range of 1.51 and 1.72eV and the notable change of the band gaps due to annealing temperatures was observed. Finally, the Urbach energies were calculated and it was observed that the band tail energies were increasing with increasing annealing temperature.