Mg doping reduced full width at half maximum of the near-band-edge emission in Mg doped ZnO films

Sol--gol method was employed to synthesize Mg doped ZnO films on Si substrates. The annealing temperature-dependent structure and optical property of the produced samples were studied. An interesting result observed is that increasing Mg concentration in the studied samples induces the full width at half maximum （FWHM） of their near-band-edge （NBE） emission decrease and the defect related emission of the corresponding sample suppresses drastically. The possible mechanism of the observed result is discussed.

Improved efficiency and stability of perovskite solar cells with molecular ameliorating of ZnO nanorod/perovskite interface and Mg-doping ZnO

Despite the advanced efficiency of perovskite solar cells(PSCs),electron transportation is still a pending issue.Here the polymer polyvinylpyrrolidone(PVP)is used to enhance the electron injection,which is thanks to the passivation of the defects at the interface between the ZnO electron transporting layer(ETL)and the perovskite.The application of the PVP layer inhibits the device degradation,and 80%of the primary efficiency is kept after 30 d storage in air condition.Additionally,the efficiency of the device is further enhanced by improving the conductivity and crystallinity of the ZnO ETL via Magnesium(Mg)doping in the ZnO nanorods(ZnO NRs).Moreover,the preparation parameters of the ZnO NRs are optimized.By employing the high-crystallinity ZnO ETL and the PVP layer,the power conversion efficiency(PCE)of the champion device is increased from 16.29%to 19.63%.These results demonstrate the advantages of combining mesoscale manipulation with interface modification and doping together.

Structural, Optical and Photocatalytic Properties of Cu2+ Doped ZnO Nanorods with Using HMTA Solvent Prepared by Hydrothermal Method

In this experiment, Cu2+ doped ZnO (Cu-ZnO) nanorods materials have been fabricated by hydrothermal method. Cu2+ ions were doped into ZnO with ratios of 2, 5 and 7 mol.% (compared to the mole’s number of Zn2+). The hexamethylenetetramine (HMTA) solvent used for the fabrication of Cu-ZnO nanorods with the mole ratio of Zn2+:HMTA = 1:4. The characteristics of the materials were analyzed by techniques, such as XRD, Raman shift, SEM and UV-vis diffuse reflectance spectra (DRS). The photocatalytic properties of the materials were investigated by the decomposition of the methylene blue (MB) dye solution under ultraviolet light. The results show that the size of Cu-ZnO nanorods was reduced when the Cu2+ doping ratio increased from 2 mol.% to 7 mol.%. The decomposition efficiency of the MB dye solution reached 92% - 97%, corresponding to the Cu2+ doping ratio changed from 2 - 7 mol.% (after 40 minutes of ultraviolet irradiation). The highest efficiency for the decomposition of the MB solution was obtained at a Cu2+ doping ratio of 2 mol.%.

Enhanced Spin Injection into ZnO Semiconductor Measured by Magnetoresistance

We prepare 2× （NiFe/CoZnO）/ZnO/（CoZnO/Co）×2 spin valve structures used for spin injection by sputtering and photolithography. In the junctions, the free magnetic layer 2× （NiFe/CoZnO） and the fixed magnetic layer （CoZnO/Co） × 2 are used to realize the spin valve functions in the external switch magnetic field. Since the wide gap semiconductor ZnO layer is located between the two magnetic semiconductor layers CoZnO, the electrical ,spin injection from the magnetic semiconductor CoZnO into the non-magnetic semiconductor ZnO is realized. Based on the measured magnetoresistance and the Schmidt model, the spin polarization ratio in the ZnO semiconductor is deduced to be 11.7% at 90K and 7.0% at room temperature, respectively.

High efficient Al: ZnO based bifocus metalens in visible spectrum

The optical components of the visible light band are widely used in daily life and industrial development. However due to the serious loss of light and the high cost, the application is limited. The broadband gap metasurface will change this situation due to its low absorption and high efficiency. Herein, we simulate a size-adjustable metasurface of the Al doped ZnO (AZO) nanorod arrays based on finite difference time domain method (FDTD) which can realize the conversion of amplitude polarization and phase in the full visible band. The corresponding theoretical polarization conversion efficiency can reach as high as 91.48% (450 nm), 95.27% (530 nm), and 91.01% (65 nm). The modulation of focusing wavelength can be realized by directly adjusting the height of the AZO nanorod. The designed half-wave plate and metalens can be applied in the imaging power modulation halfwave conversion and enriching the spectroscopy.

Highly stable Ga-doped ZnO/polystyrene nanocomposite film with narrow-band cyan emission

In the present study,a simple method for the preparation of a luminescent flexible gallium doped zinc oxide(GZO)/polystyrene nanocomposite film was developed.The prepared GZO powder was characterized through different optical and structural techniques.The XRD study revealed the existence of a wurtzite structure with no extra oxide peaks.Elemental-mapping,EDX,FTIR and XPS analyses were used to confirm the presence of elements and the several groups present in the structure.Under excitations of UV,the prepared hybrid nanocomposite showed a strong cyan emission with narrow full width at half the maximum value(20 nm)that has not been reported before.X-ray and laser-induced luminescence results of the hy-brid film revealed novel blue-green emission at room temperature.The prepared composite film showed a strong scintillation re-sponse to ionizing radiation.The strong emissions,very weak deep-level emissions,and low FWHM of composite indicate the de-sirable optical properties with low-density structural defects in the GZO composite structure.Therefore,the prepared hybrid film can be considered to be a suitable candidate for the fabrication of optoelectronic devices.

Preparation and Gas-sensing Characteristics of Na^+-doped ZnO Single Crystals

ZnO single crystals were grown by vapor phase reaction of Zno powder with active carbon powdei at an elevated temperature The typical crystals were colorless and transparent with maximum size o4 0.1 mm in diameter and 25 mm in length, The gas-sensing characteristics of Na+-doped anc undoped single crystals were investigated in 1 %H2. Co and CH, in air between 1 50 and 600℃. It was found that the undoped ZnO single crystals showed little gas sensitivity in air. and Na+-doping can greatly enhance the senstivity by increasing the resistivities. The maximum sensitivity of the samples is 22 (Ra/ Rg) for H2. 1 2 for CO and 4 for CH4

Tailoring the structural and magnetic properties of Cu-doped ZnO by c-axis pressure

The structural and magnetic properties of the Cu-doped ZnO（ZnO：Cu） under c-axis pressure were studied using first-principle calculations. It was found that the ZnO：Cu undergoes a structural transition from Wurtzite to Graphite-like structure at a c-axis pressure of 7–8 GPa. This is accompanied by an apparent loss of ferromagnetic stability, indicating a magnetic transformation from a ferromagnetic state to a paramagnetic-like state. Further studies revealed that the magnetic instability is closely related to the variation in crystalline field originated from the structural transition, which is in association with the overlapping of spin–charge density between the Cu^2＋ and adjacent O^2-.

Preparation of Rod-like Aluminum Doped Zinc Oxide Powders by Sol-gel Technique Using Metal Chlorides and Acetylacetone Precursors

Al-doped ZnO(AZO) powders were prepared by using metal chloride precursors and the sol-gel technique. IR peaks observed at 1590 cm-1 and 1620 cm-1indicated the formation of metal chelate as a consequence of the addition of acetylacetone to the metal chloride solution. TG-DSC analysis of the AZO gels confirmed the formation of metal chelate as evidenced by the development of several weight loss peaks accompanied by the introduction of new endothermic peaks. The resulting AZO gels were annealed at 500, 600, and 800 ℃ to study the effect of annealing temperature. XRD and SEM results showed that crystallization of AZO gels takes place around 600 ℃. Hexagonal wurtzite structure was identified as the main phase for all the samples. In addition, small shift of the XRD(002) peak coupled with XPS results from the AZO powders confirmed the successful doping of the ZnO powders. Micron sized rod-like AZO powders were uniform in dimension and morphology and remained stable even at 800 ℃.

Effect of samarium doping on structural, optical and magnetic properties of vertically aligned ZnO nanorod arrays

Samarium doped vertically aligned one dimensional ZnO nanorod（NR） arrays were grown by vapor phase transport（VPT） method through vapor solid（VS） growth process. Influence of different concentrations（0% to 8%） of Sm（all Sm contents in the paper are in mass fraction） on the ZnO NR arrays were investigated by X-ray diffraction（XRD）, field emission scanning electron microscopy（FESEM）, photoluminescence（PL）, Raman spectroscopy and vibrating sample magnetometry（VSM） techniques, respectively. X-ray diffraction studies revealed that the ZnO NR arrays were perfectly oriented along（002） crystallographic orientation with wurtzite crystal structure. Photoluminescence results showed an increase in oxygen vacancies due to increase in Sm doping. M-H curves revealed enhanced ferromagnetic behavior, and the magnetic moment values were 0.45, 0.363, 1.694, 3.613 and 2.197 emu/cm^3 for（0–8%） Sm doped ZnO NR arrays respectively. The curve revealed that paramagnetic behavior was observed for undoped ZnO NR arrays and on increasing the Sm dopant to 4%, paramagnetic switched to ferromagnetic behavior.

Fabrication and Characterization of Well-Aligned Zn1-xMnxO Nanorods

Well-Migned Zn1-xMnxO nanorods have been synthesized successfully on bare silicon substrates by a simple evaporation method without using any catalyst. X-ray diffraction and electron microscopy studies demonstrate that the as-grown nanorods are of single wurtzite phase with a preferential growth direction along their c- axes, Quantitative energy-dispersive spectrum analysis reveals that the concentration of manganese is around 4 at,%, Magnetic measurements show the single-phase Zn1-xMnxO nanorod arrays exhibiting the paramagnetic behaviour. Photolumlnescence spectra demonstrate that the Zn1-xMnxO nanorods preserve ultraviolet emission at room temperature.

High-quality ZnO growth, doping, and polarization effect

The authors have reported their recent progress in the research field of ZnO materials as well as the corresponding global advance. Recent results regarding（1） the development of high-quality epitaxy techniques,（2） the defect physics and the Te/N co-doping mechanism for p-type conduction, and（3） the design, realization,and properties of the ZnMgO/ZnO hetero-structures have been shown and discussed. A complete technology of the growth of high-quality ZnO epi-films and nano-crystals has been developed. The co-doping of N plus an isovalent element to oxygen has been found to be the most hopeful path to overcome the notorious p-type hurdle. High mobility electrons have been observed in low-dimensional structures utilizing the polarization of ZnMgO and ZnO.Very different properties as well as new physics of the electrons in 2DEG and 3DES have been found as compared to the electrons in the bulk.

Effect of rGO support on Gd@ZnO for UV-visible-light driven photocatalytic organic pollutant degradation

In this manuscript,we report the hydrothermally prepared rGO/Gd@ZnO nanocomposite for the utilization of photocatalytic Rh B(rhodamine B)dye degradation.The required characterization techniques were carried out to analyse the structural,morphological,chemical,environmental and optical behaviour of the prepared nanoparticles.Photocatalytic efficiency of the prepared nanoparticles was studied by Rh B dye degradation upon UV-Vis-light illumination which reveals that composite catalyst degrades the dye molecule about 91%after 40 min of irradiation.On comparing the higher degradation efficiency of the rGO/Gd@ZnO nanocomposite with that of ZnO and Gd doped ZnO,it reveals a greater reduction of charge carriers'recombination,higher visible-light utilization and higher adsorption efficiency.Elemental trapping experiment and recycling test were conducted to study the influence of active radicals for the degradation reaction and to know the stability of the prepared nanocomposite,respectively.Hence,this rGO supported Gd doped ZnO nanocomposite can provide a new path way in preparing a highly efficient photocatalyst for organic pollutant degradation at large.

Thermoelectric properties of Al-doped ZnO: experiment and simulation

Advancement in doping other elements,such as Ce,Dy,Ni,Sb,In and Ga in ZnO^（[1]）,have stimulated great interest for high-temperature thermoelectric application.In this work,the effects of Al-doping in a ZnO system on the electronic structure and thermoelectric properties are presented,by experiment and calculation.Nanosized powders of Zn_（1-x）Al_xO（x=0,0.01,0.02,0.03 and 0.06） were synthesized by hydrothermal method.From XRD results,all samples contain ZnO as the main phase and ZnAl_2O_4（spinel phase） peaks were visible when Al additive concentrations were just 6 at%.The shape of the samples changed and the particle size decreased with increasing Al concentration.Seebeck coefficients,on the other hand,did not vary significantly.They were negative and the absolute values increased with temperature.However,the electrical resistivity decreased significantly for higher Al content.The electronic structure calculations were carried out using the open-source software package which is based on DFT The energy band gap,density of states of Al-doped ZnO were investigated using PAW pseudopotential method within the LDA ＋ U.The calculated density of states was then used in combination with the Boltzmann transport equation^（[3]） to calculate the thermoelectric parameters of Al-doped ZnO.The electronic band structures showed that the position of the Fermi level of the doped sample was shifted upwards in comparison to the undoped one.After doping Al in ZnO,the energy band gap was decreased,Seebeck coefficient and electrical conductivity were increased.Finally,the calculated results were compared with the experimental results.The good agreement of thermoelectric properties between the calculation and the experimental results were obtained.

Influence of Co Content on Raman and Photoluminescence Spectra of Co Doped ZnO Nanowires

Co doped ZnO nanowires with different Co contents have been fabricated by a chemical vapor deposition method. X-ray diffraction results show that all the samples are of single phase and crystallize in wurtzite ZnO structure. The lattice parameter a increases with increasing Co content, while the parameter c has no obvious change with increasing Co. Raman spectra show that the nonpolar E2（High） mode becomes broad and weak with the doping of Co, which indicates that the incorporation of Co causes structural disorder in the crystalline columnar ZnO lattice. The photolurninescence spectra exhibit that the position of the ultraviolet emission shifts to short wavelength and the intensity decreases with increasing Co. The green emission is affected by two contrary factors. It is increased by the introduced defects, but suppressed by the interaction between Co doping and native defects and the later affects it more significantly.

Structural,optical,morphological and electrical properties of undoped and Al-doped ZnO thin films prepared using sol–gel dip coating process

In this work,sol-gel dip-coating technique was used to elaborate ZnO pure and ZnO/Al films.The impact of Al-doped concentration on the structural,optical,surface morphological and electrical properties of the elaborated samples was investigated.It was found that better electrical and optical performances have been obtained for an Al concentration equal to 5%,where the ZnO thin films exhibit a resistivity value equal to 1.64104 Ω·cm.Moreover,highest transparency has been recorded for the same Al concentration value.The obtained results from this investigation make the developed thin film structure a potential candidate for high optoelectronic performance applications.

Photocatalytic activity of Eu-doped ZnO prepared by supercritical antisolvent precipitation route:When defects become virtues

The aim of this work is to determine the structural and optical properties of Eu-doped ZnO powders prepared by supercritical antisolvent precipitation route(SAS)and to correlate the physico-chemical features with the photocatalytic activity under UV light.Raman and EPR spectroscopy highlight the introduction of novel defects(mainly singly and doubly ionized oxygen vacancies,and oxygen interstitials)on the Eu-doped ZnO samples,which confer higher hydrophilicity to the doped samples with respect to bare ZnO,as evidenced by FT-IR analysis.Additionally,photoluminescence spectra show that the presence of Eu^(3+) totally quenches the visible light emission typical of bare ZnO,which mainly results from the recombination of photogenerated holes at defective sites.The prepared samples were tested both for the photocatalytic degradation of crystal violet dye(CV)and for the partial oxidation of ferulic acid under UV irradiation.The photocatalytic activity results evidence of a higher ability of Eu-doped photocatalysts to degrade CV and ferulic acid,while higher selectivity values towards vanillin are obtained in the presence of bare ZnO.The higher activity of Eu-doped ZnO photocatalysts is linked to the stabilization of photogenerated holes and to their higher hydrophilicity,both brought by the generation of defective sites induced by the presence of Eu^(3+) ions within the ZnO lattice.

Highly transparent low resistance Ga doped ZnO/Cu grid double layers prepared at room temperature

Ga doped ZnO （GZO）/Cu grid double layer structures were prepared at room temperature （RT）. We have studied the electrical and optical characteristics of the GZO/Cu grid double layer as a function of the Cu grid spacing distance. The optical transmittance and sheet resistance of the GZO/Cu grid double layer are higher than that of the GZO/Cu film double layer regardless of the Cu grid spacing distance and increase as the Cu grid spacing distance increases. The calculated values for the transmittance and sheet resistance of the GZO/Cu grid double layer well follow the trend of the experimentally observed transmittance and sheet resistance ones. For the GZO/Cu grid double layer with a Cu grid spacing distance of 1 mm, the highest figure of merit （ФTC = 6.19 × 10^-3 Ω^-1） was obtained. In this case, the transmittance, resistivity and filling factor （FF） of the GZO/Cu grid double layer are 83.74%, 1.10 ×10^-4Ω.cm and 0.173, respectively.

Facile Synthesis as well as Structural, Raman, Dielectric and Antibacterial Characteristics of Cu Doped ZnO Nanoparticles

Here, undoped and Cu doped ZnO nanoparticles(NPs) have been prepared by chemical co-precipitation technique. X-ray diffraction(XRD) results reveal that Cu ions are successfully doped into ZnO matrix without altering its wurtzite phase. The single wurtzite phase of ZnO is retained even for 10 wt% Cu doped ZnO sample. It is observed from the electron microscopy results that higher level of Cu doping varies the morphology of ZnO NPs from spherical to flat NPs. Moreover, the particle size is found to increase with the increase in Cu doping level. Raman spectroscopy results further confirm that Cu dopant has not altered the wurtzite structure of ZnO. Impedance spectroscopy results reveal that the dielectric constant and dielectric loss have increasing trend with Cu doping. Cu doping has been found to slightly decrease the bactericidal potency of ZnO nanoparticles.