Optical properties of Cu-doped ZnO nanoparticles experimental and first-principles theory research

Zn_1?x Cu _x O nanoparticles were synthesized by using sol–gel method. Structure and optical properties of Zn_1?x Cu _x O nanoparticles were studied experimentally and theoretically. The simulations are based upon the Perdew-Burke-Ernzerhof form of generalized gradient approximation within the density functional theory. The results showed that the UV emission is effectively quenched and the emission in visible-light region is enhanced by Cu-doping, which are theoretically explained to be attributed to the electronic intra-band transition from the occupied bands to the unoccupied ones under irradiation. Therefore, Zn_1?x Cu _x O system may be a potential candidate for photocatalytic in visible light range.     

Effects of dopants on magnetic properties of Cu-doped ZnO thin films

We report the observation of room temperature ferromagnetism (FM) in Cu-doped ZnO (ZnO: Cu) thin films synthesized by sol–gel technique. While donor Al³⁺ cations are introduced into the ZnO: Cu films, the saturation magnetization decreases rapidly. Cu 2p core-level X-ray photoelectronic spectra demonstrate that the FM is strongly correlated with Cu²⁺ cations (3d ⁹ configuration). To further study the relationship between the FM and acceptors, Na⁺ cations are also introduced into the ZnO: Cu films to increase the saturation magnetization. The enhanced FM in the (Cu, Na)-codoped ZnO is suggested to be due to the hybridization between delocalized holes and spin-split Cu 3d states.     

Cu掺杂ZnO纳米粒子的光学性能及铁磁性

利用溶胶凝胶法制备了纳米结构的Cu掺杂ZnO基稀磁半导体,通过X射线衍射分析表明,样品为纯相ZnO纤锌矿结构,磁性测量表明样品在室温下呈室温铁磁性,铁磁性来源为氧化锌晶格中的缺陷与Cu2＋离子之间的交换作用。室温光致发光（PL）谱观察到紫外带边和可见光区两个发射峰,且随着Cu掺杂量增加,紫外峰淬灭,可见峰发射增强。     

Optical and magnetic properties of Ni-doped ZnO nanocones

Ni-doped ZnO flower-like nanocones with wurzite structures were produced by oxidative evaporation of Zn and Ni powders. The Ni doping did not change the ZnO wurtzite structure. Raman scattering indicated that the normal lattice vibration modes are related to the hexagonal ZnO. Ni clusters and Ni oxides phases did not existed in the sample as characterized by XRD, XPS, and TEM. Upon excitations the nanocones could emit strong green light at 525 nm, which can be directly observed with a digital camera. The magnetic measurement indicated that the Ni-doped ZnO nanocone was high-Curie-temperature magnetic semiconductor.     

Ferromagnetism in Cu-doped ZnO nanoparticles at room temperature

Cu-doped ZnO nanoparticles were successfully synthesized and structurally characterized by using X-ray diffraction (XRD) and transmission electron microscope (TEM). XRD shows that Zn_1−xCu_xO (x ≤ 0.04) samples are single phase with the ZnO-like wurtzite structure, while the secondary phase Cu is observed in Zn_0.95Cu_0.05O sample. Magnetic measurements indicated that Zn_1−xCu_xO (x = 0.02, 0.03, 0.04) are ferromagnetic at room temperature and the magnetic moment per Cu atom decreased with increasing Cu concentration. XRD, TEM and X-ray photoelectron spectroscopy (XPS) analysis revealed that no ferromagnetic-related secondary phase was detected. The origin of the ferromagnetism in Zn_1−xCu_xO (x ≤ 0.04) was mainly due to Cu ions substituted into the ZnO lattice.     

Structural,optical and magnetic characterization of Cu-doped ZnO nanoparticles synthesized using solid state reaction method

Polycrystalline undoped and Cu-doped Zinc oxide (Zn_0.98Cu_0.02O) nanocrystals were successfully synthesized by solid-state reaction method. The micro structural, optical and magnetic properties have been characterized using powder X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive analysis using X-rays (EDAX), UV–Visible spectroscopy, Photoluminescence, Vibrating sample magnetometer and Electron paramagnetic resonance spectroscopy. XRD pattern reveals that the samples possess hexagonal wurtzite structure of ZnO without any secondary phase after copper doping. Optical absorption analysis of the samples showed a red shift in absorption band edge with copper doping in ZnO. Photoluminescence spectra of the samples shows prominent peaks corresponding to near band edge UV emission and defect related green emission in the visible region at room temperature and their possible mechanism have also been discussed. Magnetic measurements using VSM showed that the nanocrystalline copper doped ZnO exhibits ferromagnetic behaviour at 300 K. EPR analysis also confirms the substitution of Zn site by Cu²⁺.     

Room-temperature ferromagnetic properties of Cu-doped ZnO rod arrays

We have investigated properties of the Cu-doped ZnO crystalline film synthesized by the hydrothermal method. X-ray diffraction and X-ray photoelectron spectroscopy results provide the evidence that Cu^2 + is incorporated into the ZnO lattices. Photoluminescence spectrum of the rod arrays shows that the UV emission peak shifts a little to lower energy and its intensity decreased. There are another two emission peaks centred in blue and green regions because of the incorporation of Cu^2 + ions. The rod arrays have exhibited room-temperature ferromagnetic behaviour with the remanence of 0·926 × 10^− 3 emu/cm³. We suggest that the exchange interaction between local spin-polarized electrons (such as the electrons of Cu^2 + ions) and conductive electrons is the cause of room-temperature ferromagnetism.     

Synthesis and systematic investigations of Al and Cu-doped ZnO nanoparticles and its structural,optical and photo-catalytic properties

Here we report, copper (Cu) and Aluminum (Al) doped zinc oxide (ZnO) nanoparticles by a novel one step microwave irradiation method for the first time. Powder X-ray diffraction (XRD) reveals that both pure and doped samples assigned to hexagonal wurtzite type structure. The calculated average crystalline size decreases from 24 to 11 nm for pure and doped (Al and Cu) ZnO respectively, which is in good agreement with the particles size observed from Transmission Electron Microscope (TEM) analyses. A considerable red shift in the absorption edge and the reduction in the energy gap from 3.35 to 2.95 eV reveal the substitution of Al³⁺ and Cu²⁺ ions into the ZnO lattice analyzed by UV–Vis transmission spectra. The photocatalytic degradation of Methyl Violet (MV), Phenol and Rhodamine B (RHB) was investigated by using pure, Al and Cu doped ZnO catalyst under UV light irradiation. The results showed that the photocatalytic property is significantly improved by Cu doping concentration. This could be attributed to extended visible light absorption, inhibition of the electronehole pair’s recombination and enhanced adsorptivity of dye molecule on the surface of Cu–ZnO nanopowders. The samples were further characterized by photoluminescence spectra and Fourier Infrared Spectra (FTIR) analysis.     

Room temperature optical and magnetic properties of polyvinylpyrrolidone capped ZnO nanoparticles

Defect induced room temperature ferromagnetic properties of polyvinylpyrrolidone (PVP) capped nanocrystalline ZnO samples have been studied. Crystal phase and the lattice parameter of the synthesized nanocrystalline samples have been determined from X-ray diffraction spectra (XRD) and high-resolution transmission electron micrographs (HR-TEM). Room temperature photoluminescence (PL) spectrum for the bare ZnO sample shows a strong band at ~ 379 nm and another band at ~ 525 nm. The PL spectra also revealed that the number of oxygen vacancies in the uncapped sample is more than the PVP capped sample. Both sample exhibit ferromagnetic property at room temperature when annealed at 500 °C for 3 h, due to the formation of adequate oxygen vacancy related defects. The saturation magnetization for the annealed PVP capped sample is found to be larger compared to that for the uncapped sample.     

Optical properties of the synthesized ZnO with ion implanted silver nanoparticles

Technical Physics Letters - The implantation results of a thin ZnO film formed by vacuum magnetron sputtering when irradiated by Ag+ ions with an energy of 30 keV, radiation dose of 1.5 × 1017...     

Influence of cerium dopant on magnetic and dielectric properties of ZnO nanoparticles

Ce-doped ZnO nanoparticles (NPs) with different Ce doping concentrations (0, 0.96, 1.96, 2.52 and 3.12 at.% of Ce) were prepared by the chemical co-precipitation method. Energy-dispersive analysis of X-rays confirms the presence of Ce in Ce-doped ZnO nanoparticles. Raman spectra revealed the hexagonal wurtzite structure of pure and Ce-doped ZnO nanoparticles and presence of various defects. The photoluminescence spectra exhibited enhanced violet and blue emission peak intensities for 0.96 at.% of Ce, while broad band green emissions decreased with Ce content. Electron paramagnetic resonance (EPR) studies revealed the presence of oxygen vacancies (V _O), zinc vacancies (V _Zn) and Ce³⁺ ions in the prepared ZnO nanoparticles. VSM studies showed room temperature ferromagnetism (RTFM) in the Ce-doped ZnO NPs. The substituted Ce³⁺ions found to induce RTFM along with V _O, V _Zn in correlation with the results obtained from the EPR, PL and Raman studies. The variation of dielectric constants (ε _r), dielectric loss (ε″) and ac conductivity (σ _ac) as a function of frequency and Ce concentration is studied using ‘Maxwell–Wagner Model.’     

Physical and magnetic properties of (Co, Ag) doped ZnO nanoparticles

Undoped and (Co, Ag) co-doped ZnO nanostructure powders are synthesized by chemical precipitation method without using any capping agent and annealed in air ambient at 500 °C for 1 h. Here, the Ag concentration is fixed at 5 mol% and Co concentration is increased from 0 to 5 mol%. The X-ray diffraction studies reveal that undoped and doped ZnO powders consist of pure hexagonal structure and nano-sized crystallites. The novel Raman peak at 530 cm^?1 has corroborated with the Co doped ZnO nanoparticles. Moreover, the PL studies reveal that as the Co doping concentration increases and it enters into ZnO lattice as substitutional dopant, it leads to the increase of oxygen vacancies (Vo) and zinc interstitials (Zn_i). From the magnetization measurements, it is noticed that the co-doped ZnO nanostructures exhibit considerably robust ferromagnetism i.e. 4.29 emu g^?1 even at room temperature. These (Co, Ag) co-doped ZnO nanopowders can be used in the fabrication of spintronic and optoelectronic device applications.     

Structure and magnetic properties of (Co,Mn) co-doped ZnO diluted magnetic semiconductor nanoparticles

The ZnO, Zn_0.96Mn_0.04O, Zn_0.95Mn_0.04Co_0.01O, Zn_0.94Mn_0.04Co_0.02O and Zn_0.92Mn_0.04Co_0.04O nanoparticles were synthesized by simple chemical precipitation technique. The effects of co-doping on the structure and magnetic properties of these nanoparticles were studied. The X-rays diffraction (XRD) scans were performed in the 2θ range of 20°–80°. The XRD patterns, at 300 K, of all the pure and co-doped ZnO samples confirmed the formation of wurtzite-type structure. X-ray diffraction and transmission scanning electron microscope analysis indicated that the high spin Co²⁺ and Mn²⁺ ions were substituted for the Zn²⁺ ions at tetrahedral sites. The average size of the nanoparticles were increased from 17 to 24 nm with the increase of dopants concentration. Moreover, Energy Dispersive X-ray spectroscopy (EDX) confirmed the synthesis results. All Zn_0.96?xMn_0.04Co _x O (x?=?0.0, 0.1, 0.2 and 0.4) nanoparticles samples were observed to be paramagnetic below 300 K. However, a large increase in the magnetization was observed below 40 K. This behavior, along with the negative value of the Curie–Weiss constant obtained from the linear fit to the susceptibility data below room temperature, indicated the ferromagnetic nature of the samples. The origin of ferromagnetism is likely to be the intrinsic characteristics of the Co and Mn doped samples. The high magnetization was noted for the 1 wt% Co co-doped Mn–ZnO annealed samples as compared to other samples with Co concentration above and below this threshold concentration.     

Magnetic properties of ZnO nanoparticles

We experimentally show that it is possible to induce room-temperature ferromagnetic-like behavior in ZnO nanoparticles without doping with magnetic impurities but simply inducing an alteration of their electronic configuration. Capping ZnO nanoparticles ( approximately 10 nm size) with different organic molecules produces an alteration of their electronic configuration that depends on the particular molecule, as evidenced by photoluminescence and X-ray absorption spectroscopies and altering their magnetic properties that varies from diamagnetic to ferromagnetic-like behavior.     

Optical and magnetic properties of copper doped ZnO nanorods prepared by hydrothermal method

Surfactant free ZnO and Cu doped ZnO nanorods were synthesized by hydrothermal method. The formation of ZnO:Cu nanorods were confirmed by scanning electron microscopy, X-ray diffraction and Raman analysis. Diffuse reflectance spectroscopy results shows that band gap of ZnO nanorods shifts to red with increase of Cu content. The orange-red photoluminescent emission from ZnO nanorods originates from the oxygen vacancy or ZnO interstitial related defects. ZnO:Cu nanorods showed strong ferromagnetic behavior, however at higher doping percentage of Cu the ferromagnetic behavior was suppressed and paramagnetic nature was enhanced. The presence of non-polar E ₂ ^high and E ₂ ^low Raman modes in nanorods indicates that Cu doping didn’t change the wurtzite structure of ZnO.     

Optical properties of ZnO nanostructures

We present a review of current research on the optical properties of ZnO nanostructures. We provide a brief introduction to different fabrication methods for various ZnO nanostructures and some general guidelines on how fabrication parameters (temperature, vapor-phase versus solution-phase deposition, etc.) affect their properties. A detailed discussion of photoluminescence, both in the UV region and in the visible spectral range, is provided. In addition, different gain (excitonic versus electron hole plasma) and feedback (random lasing versus individual nanostructures functioning as Fabry-Perot resonators) mechanisms for achieving stimulated emission are described. The factors affecting the achievement of stimulated emission are discussed, and the results of time-resolved studies of stimulated emission are summarized. Then, results of nonlinear optical studies, such as second-harmonic generation, are presented. Optical properties of doped ZnO nanostructures are also discussed, along with a concluding outlook for research into the optical properties of ZnO.     

Optical and magnetic properties of Mn doped ZnO samples prepared by solid state route

The structural, optical and magnetic properties of Zn_1?xMn_xO (x = 0.02, 0.04 and 0.06) prepared by solid state route are presented. The rietveld refined X-ray data revealed single hexagonal phase with the space group P63mc in all samples. Significant blue shift with Mn doping is observed in UV–Visible studies, supported by photoluminescence spectra showing a high intensity UV emission peak followed by the low intensity green emission band corresponding to oxygen vacancies and defects. Photoluminescence spectra also suggested that doping of Mn can affect defects and oxygen vacancies in ZnO and giving the possibility of band gap tuning for potential applications in optoelectronic devices. All single-phase samples exhibit paramagnetic behaviour at room temperature, involving small proportion of defect mediated ferromagnetic ordering.     

Optical and magnetic properties of Mn doped ZnO thin films grown by SILAR method

Polycrystalline Mn doped ZnO (MZO) semiconductor thin films were deposited onto glass substrates employing different number of dipping at room temperature using Successive Ionic Layers by Adsorption Reaction (SILAR) technique. The thin film deposition conditions were optimized by altering the various deposition parameters based on their structure. The structural study was carried out using X-ray diffractometer (XRD). The XRD analysis indicated that there is no change in the structure of ZnO thin films due to Mn doping. The films exhibited hexagonal wurtzite structure. The structural studies on Mn doped samples revealed that the predominant orientation is (002) lattice plane and the position of this orientation shifted toward lower angle during doping. The intensity of photoluminescence (PL) emission of ZnO is found to be augmented for Mn doped samples. The room temperature Raman spectra measurements revealed the presence of additional modes. The Vibrating Sample Magnetometer (VSM) studies show that MZO thin film has ferromagnetic properties.