Figure - available from: Journal of Superconductivity and Novel Magnetism
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The crystalline structure of alloys Zn1−xNixO for x = (0.125, 0.062, and 0.028). Light blue, violet, and dark red spheres are representative for Ni, Zn, and O, respectively
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The magnetic properties of Ni-doped ZnO nanoparticles are investigated using a numerical model based on simultaneous solution of the localized partition function and the master equation of particle moment dynamics. In this model, field-cooled and zero field-cooled (FC/ZFC) magnetization and the hysteresis loop are calculated. To provide an accurate...
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High sensitivity ammonia (NH3) gas sensor based on nickel-doped ZnO (NZO) hexagonal microdisc like-nanostructures is reported in this work. Field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) revealed that the undoped ZnO revealed interconnected hexagonal microdiscs transformed into hollow square shaped in...
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We demonstrate RF sputtered Ni-doped ZnO nanostructures for detection of extremely low concentration (1 ppm) of hydrogen gas at moderate operating temperature of 75 °C. Structural, morphological, electrical and hydrogen sensing behavior of the Ni-doped ZnO nanostructures strongly depends on doping concentration. Ni doping exceptionally enhances the...
In this study, the effect of Sr- and Ni-doping on the microstructural, morphological and sensing properties of ZnO nanorods has been investigated. Nanorods with different Sr and Ni loadings were prepared using a simple wet chemical method and characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence...
Zinc oxide is one of the most important semiconducting metal oxides and one of the most promising n-type materials, but its practical use is limited because of both its high thermal conductivity and its low electrical conductivity. Numerous studies have shown that doping with metals in ZnO structures leads to the modification of the band gap energy...
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... To resolve this issue doping is popular way to achieve the efficiency as well as to adjust the band gap [48][49][50]. Among various dopants like copper, silver, Mn, Co, Eu, Ce, Gd, La, Ni, Al used by researchers [51][52][53][54][55][56][57][58][59][60][61][62]. Sn doped ZnO has gained much attention because it has good oxidation rate and can substitute into Zn lattice without any difficulty [63]. ...
We have fabricated ZnO nano rods by hydrothermal method and successively doped them with tin (Sn) using different concentrations of 25, 50, 75 and 100 mg of tin chloride. XRD of the fabricated structures showed that ZnO possess hexagonal wurtzite phase. Scanning electron microscopy (SEM) was used to explore the morphology and it shows nanorod like morphology for all samples and no considerable change in the structural features were found. The dimension of nanorod is 200 to 300 nm. The doped materials were then investigated for their photo catalytic degradation of environmental pollutant Rhodamine B. The performance of doped ZnO is compared with the pristine ZnO. Scanning electron microscopy (SEM) was used to explore the morphology and it shows nanorod like morphology for all samples and no considerable change in the structural features were found. The dimension of nanorod is 200 to 300 nm. XRD of the fabricated structures showed that ZnO possess hexagonal wurtzite phase. Photo catalytic activity of rhodamine B was investigated under UV light and a maximum degradation efficiency of 85% was obtained. The optical property reveals the reduction in band gap of upto 17.14% for 100 mg Sn doped ZnO. The degradation is followed by the pseudo order kinetics. The produced results are unique in terms of facile synthesis of Sn doped ZnO and excellent photo degradation efficiency, therefore these materials can be used for other environmental applications.
... These results were consistent with the variation trend of previous experimental findings with similar doping amounts. 8 Considering the unipolar structure of ZnO, the calculated results of formation energy of all doped systems are shown in Table I. As shown in Table I magnetic moment of the first system Zn 15 NiO 16 was calculated as 2 l B (l B is Bohr magneton). ...
... . Compared with the lattice parameters of Zn16 O 16 , those of Zn15 NiO 16 along the c-axis decreased in accordance with the experimental values,8 indicating that the lattice parameter setting was reasonable. The volumes of all the doping system models were calculated when Ni doping coexisted with Zn vacancy or O vacancy decreased because the Ni 2þ radius (0.069 nm)16 is smallerTABLE I. Total energy, formation energy of doping system, Zn vacancy or O vacancy, as well as lattice constants of Zn 16 O 16 ,Z n 15 NiO 16 ,Z n 14 NiO 16 , and Zn 15 NiO 15 after geometric structure optimization. ...
The magnetism sources and magnetic mechanism of Ni-doped ZnO remain unknown to date. In this study, the plane-wave ultrasoft pseudopotential technology of generalized gradient approximation +U based on spin-density-functional theory was used to investigate the magnetism sources and magnetic mechanism of Ni-doped ZnO. Results showed that the total magnetic moment of the ZnO system with Ni doping and O vacancy was similar to that of Ni-doped ZnO. Compared with the ZnO system with Ni doping and O vacancy, the doping system with Ni doping and Zn vacancy exhibited a larger magnetic moment, smaller formation energy, and better stability, and it was easier to dope. The magnetism of the Zn14NiO16 system mainly resulted from the hybrid coupling electron exchange effect among the O-2p (nearest to the Zn vacancy and Ni atom), Ni-3d, and Zn-4s orbits. This effect was based on the hole carriers in the complex as the medium. In the ZnO system with Ni doping and Zn vacancy, the magnetic moment slightly decreased with increasing doping amount. Results showed that the system with Ni doping and Zn vacancy was ferromagnetic. In addition, the Curie temperature of the doping system was at room temperature.
... Doping is a common way to adjust the band gap of ZnO base. Mn [13], Cu [14], Co [15], Al [16], Ni [17,18], La [19], Gd [20], Ce [21], Tb [22] and Eu [23] has been used to dope ZnO in recent years. Sn doped ZnO has attracted lots of attention these years [24][25][26][27]. ...
An ultrasonic method is employed to synthesize the Sn doped Zn0.95Sn0.05Oquantum dots with green light emission. Sn²⁺ and Sn⁴⁺ ions are used to create different optical defects inside Zn0.95Sn0.05O quantum dots and the changing trend of oxygen concentration under different ultrasonic irradiation power are investigated. The photoluminescence spectra are employed to characterize the optical defects of Zn0.95Sn0.05O quantum dots. The UV-vis spectra are used to study the band gap of Zn0.95Sn0.05O quantum dots, which is influenced by their sizes. The results indicate that ultrasonic power would influence the size of Zn0.95Sn0.05O quantum dots as well as the type and quantity of defects in ZnO quantum dots. Changing trends in size of Sn²⁺ and Sn⁴⁺ doped Zn0.95Sn0.05O quantum dots are quite similar with each other, while the changing trends in optical defects types and concentration of Sn²⁺ and Sn⁴⁺ doped Zn0.95Sn0.05O quantum dots are different. The difference of the optical defects concentration changing between Sn²⁺ doped Zn0.95Sn0.05O quantum dots ( defects) and Sn⁴⁺ doped Zn0.95Sn0.05O quantum dots ( and defects) shows that the formation process of ZnO under ultrasonic irradiation wiped oxygen out.
Different types of scaling methods to characterize spin-glass freezing in random magnetic systems have been discussed in literature. An earlier proposed scaling method for imaginary part of ac susceptibility using a different approach is presented for 5-nm NiO particles. This work supports for the spin-glass freezing in nanoparticle systems at lower temperature.
The enhanced works of separation for the low adhesive (0 0 0 1)ZnO|(1 1 1)ZrO2 interfacess via Y-doping in ZnO slab were systematically studied using data-mining technique and density functional theory (DFT) study. The lattice constants in 31 types of doped wurtzite Zn0.9375X0.0625O were evaluated from DFT calculations. No linear correlation is found between the lattice constants and atomic radii. A support vector regression (SVR) for the lattice constants of 32 Zn0.9375X0.0625O has been performed. SVR method with leave-one-out cross-validation is used for evaluating the regression models. The correlation coefficient obtained by the models was 0.905. The accuracy of SVR model was higher than those of artificial neural network (ANN) and partial least square (PLS) methods. Zn0.9375Y0.0625O has the largest lattice constants among the investigated systems. In Y-ZnO(0 0 0 1) surface, a significant segregation phenomena occurs. Hence, dopant Y expands the lateral lattice and leaves the Zn-terminal surface intact. For coherent (0 0 0 1)Y-ZnO|(1 1 1)ZrO2 interfaces, Y-doping can enhance the work of separation significantly (∼82%) compared with the undoped (0 0 0 1)ZnO|(1 1 1)ZrO2 interfaces.
Nowadays, the experimental results of absorption spectrum distribution of Ni doped ZnO suffer controversy when the mole fraction of impurity is in a range from 2.78% to 6.25%. However, there is still lack of a reasonable theoretical explanation. To solve this problem, the geometry optimizations and energies of different Ni-doped ZnO systems are calculated at a state of electron spin polarization by adopting plane-wave ultra-soft pseudo potential technique based on the density function theory. Calculation results show that the volume parameter and lattice parameter of the doping system are smaller than those of the pure ZnO, and they decrease with the increase of the concentration of Ni. The formation energy in the O-rich condition is lower than that in the Zn-rich condition for the same doping system, and the system is more stable in the O-rich condition. With the same doping concentration of Ni, the formation energies of the systems with interstitial Ni and Ni replacing Zn cannot be very different. The formation energy of the system with Ni replacing Zn increases with the increase of the concentration of Ni, the doping becomes difficult, the stability of the doping system decreases, the band gap becomes narrow and the absorption spectrum is obviously red shifted. The Mulliken atomic population method is used to calculate the orbital average charges of doping systems. The results show that the sum of the charge transitions between the s state orbital and d state orbital of Ni²⁺ ions in the doping systems Zn0:9722Ni0:0278O, Zn0:9583Ni0:0417O and Zn0:9375Ni0:0625O supercells are all closed to +2. Thus, it is considered that the valence of Ni doped in ZnO is +2, and the Ni is present as a Ni²⁺ ion in the doping system. The ionized impurity concentrations of all the doping systems exceed the critical doping concentration for the Mott phase change of semiconductor ZnO, which extremely matches the condition of degeneration, and the doping systems are degenerate semiconductors. Ni-doped ZnO has a conductive hole polarization rate of up to nearly 100%. Then the band gaps are corrected via the LDA (local density approximation)+U method. The calculation results show that the doping system possesses high Curie temperature and can achieve room temperature ferromagnetism. The magnetic moment is derived from the hybrid coupling effect of p-d exchange action. Meanwhile, the magnetic moment of the doping system becomes weak with the increase of the concentration of Ni. In addition, the absorption spectrum of Ni-interstitial ZnO is blue-shifted in the ultraviolet and visible light bands.
The structures and band structures of Sn doped ZnO were investigated by density functional theory (DFT). Sn-doped ZnO quantum dots were also synthesized via an ultrasonic sol–gel method. The charge of Sn ions was also taken into consideration and Sn²⁺ and Sn⁴⁺ were employed. UV-Vis absorption spectra and photoluminescence excitation spectra were used to elucidate the band gap of Sn-doped ZnO QDs. Photoluminescence spectra were employed to study the change in the defects of Sn-doped ZnO QDs. Sn doping reduced the symmetry of the ZnO cell and stretched the cell. Furthermore, it also could change ZnO from a direct gap semiconductor to an indirect gap semiconductor. The experimental results and DFT calculations matched quite well. Both the DFT calculations and experimental results showed that with an increasing Sn content, the band gap of Sn-doped ZnO first decreased and then increased, whereas the band gap of the ZnO base only increased. Sn doping also changed the optical defects of the quantum dots from defects to OZn and Oi defects.
