Zn0.99Cu0.01O films were studied experimentally and theoretically. The films were prepared by pulsed-laser deposition on Pt（111）/Ti/SiO2/Si substrates under various oxygen pressures to investigate the growth-depende...Zn0.99Cu0.01O films were studied experimentally and theoretically. The films were prepared by pulsed-laser deposition on Pt（111）/Ti/SiO2/Si substrates under various oxygen pressures to investigate the growth-dependence of the ferromagnetic properties. The structural, magnetic, and optical properties were studied, and it was found that all the samples possess a typical wurtzite structure, and that the films exhibit room-temperature ferromagnetism. The sample deposited at 600 ℃ and an oxygen pressure of 10 Pa showed a large saturation magnetization of 0.83 μB/Cu. The enhanced ferromagnetism in the （Cu, Li）-codoped ZnO is attributable to the existence of Zn vacancies （Vzn）, as shown by first-principles calcu- lations. The photoluminescence analysis demonstrated the existence of Vzn in both Zn0.99Cu0.01 O and （Cu, Li）-codoped ZnO thin films, and this plays an important role in the increase of ferromagnetism, according to the results of first-principles calculations.展开更多
Zn（1-x）Cux O（x=0.00, 0.01, 0.03, and 0.05） nanoparticles are synthesized via the sol-gel technique using gelatin and nitrate precursors. The impact of copper concentration on the structural, optical, and antibacte...Zn（1-x）Cux O（x=0.00, 0.01, 0.03, and 0.05） nanoparticles are synthesized via the sol-gel technique using gelatin and nitrate precursors. The impact of copper concentration on the structural, optical, and antibacterial properties of these nanoparticles is demonstrated. Powder x-ray diffraction investigations have illustrated the organized Cu doping into ZnO nanoparticles up to Cu concentration of 5%（x = 0.05）. However, the peak corresponding to CuO for x= 0.01 is not distinguishable. The images of field emission scanning electron microscopy demonstrate the existence of a nearly spherical shape with a size in the range of 30–52 nm. Doping Cu creates the Cu–O–Zn on the surface and results in a decrease in the crystallite size. Photoluminescence and absorption spectra display that doping Cu causes an increment in the energy band gap. The antibacterial activities of the nanoparticles are examined against Escherichia coli（Gram negative bacteria）cultures using optical density at 600 nm and a comparison of the size of inhibition zone diameter. It is found that both pure and doped ZnO nanoparticles indicate appropriate antibacterial activity which rises with Cu doping.展开更多
Zn0.98Cu0.020 powders are prepared by the sol-gel method. A small number of CuO impurity phases are observed by the x-ray diffraction, indicating the solubility of Cu in ZnO is less than 2 at.%. The Zn0.98Cu0.020 powd...Zn0.98Cu0.020 powders are prepared by the sol-gel method. A small number of CuO impurity phases are observed by the x-ray diffraction, indicating the solubility of Cu in ZnO is less than 2 at.%. The Zn0.98Cu0.020 powders exhibit diamagnetism at 300 K and paramagnetism at 5 K. After subtracting the diamagnetic contribution of ZnO bulk and the paramagnetic contribution of defects, Cu ions exhibit weak paramagnetism. By codoping Cu with Co or Mn in ZnO, only paramagnetism is observed at room temperature.展开更多
Room-temperature photoluminescence and optical transmittance spectroscopy of Co-doped（1×1014,5×1016,and 1×1017cm-2） and Cu-doped（5×1016cm-2） ZnO wafers irradiated by D-D neutrons（fluence of 2....Room-temperature photoluminescence and optical transmittance spectroscopy of Co-doped（1×1014,5×1016,and 1×1017cm-2） and Cu-doped（5×1016cm-2） ZnO wafers irradiated by D-D neutrons（fluence of 2.9×1010 cm-2） have been investigated.After irradiation,the Co or Cu metal and oxide clusters in doped ZnO wafers are dissolved,and the wu¨rtzite structure of ZnO substrate for each sample remains unchanged and keeps in high c-axis preferential orientation.The degree of irradiation-induced crystal disorder reflected from the absorption band tail parameter（E0） is far greater for doped ZnO than the undoped one.Under the same doping concentration,the Cu-doped ZnO wafer has much higher irradiation-induced disorder than the Co-doped one.Photoluminescence measurements indicate that the introduction rate of both the zinc vacancy and the zinc interstitial is much higher for the doped ZnO wafer with a high doping level than the undoped one.In addition,both crystal lattice distortion and defect complexes are suggested to be formed in doped ZnO wafers.Consequently,the Co-or Cu-doped ZnO wafer（especially with a high doping level） exhibits very low radiation hardness compared with the undoped one,and the Cu-doped ZnO wafer is much less radiation-hard than the Co-doped one.展开更多
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 Wurtzit...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-.展开更多
Nanocrystalline Zn1_xCuxO （x = 0, 0.02, 0.04, 0.06, 0.08） samples were synthesized by a novel auto-combustion method using glycine as the fuel material. The structural, optical and magnetic properties of the samples...Nanocrystalline Zn1_xCuxO （x = 0, 0.02, 0.04, 0.06, 0.08） samples were synthesized by a novel auto-combustion method using glycine as the fuel material. The structural, optical and magnetic properties of the samples were characterized using XRD, SEM, photoluminescence （PL） and electron paramagnetic resonance （EPR） spectro- scopies. The XRD spectra of samples reveal the hexagonal wurtzite structures of ZnO. As the copper content increases, a diffraction peak at 28 = 39° corresponding to secondary phase of CuO （[111] crystalline face） appears when x≤ 6 mol.%. PL spectra of the samples show a strong ultraviolet （UV） emission and defect related visible emissions. Cu-doping in ZnO can effectively adjust the energy level in ZnO, which leads to red shift in the emission peak position in UV region. The EPR spectra of Cu-doped ZnO nanoparticles show a distinct and broad signal at room temperature, suggesting that it may be attributed to the exchange interactions within Cu2＋ ions.展开更多
The synthesis of Cu-doped ZnO nanosheets at room temperature was reported in our previous paper. The effects of annealing temperature on Cu-doped ZnO nanosheets were studied in this paper. Cu-doped ZnO nanosheets were...The synthesis of Cu-doped ZnO nanosheets at room temperature was reported in our previous paper. The effects of annealing temperature on Cu-doped ZnO nanosheets were studied in this paper. Cu-doped ZnO nanosheets were annealed at 200-500℃ in air. The annealed specimens were characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD） and transmission electron microscopy （TEM）. The results show that Cu concentration in Cu-doped ZnO nanosheets reduced with increasing annealing temperature. When annealing temperature was lower than Zn melting point （410℃）, the morphologies of the Cu-doped ZnO nanosheets remained nearly the same as that before annealing. However, when the annealing temperature was over Zn melting point, Cu-doped ZnO nanosheets changed to nanowires, wormlike nanosheets or did not change. The change of Cu concentration in Cu-doped ZnO nanosheets is explained by oxidation thermodynamics. A physical model is suggested to explain the morphology changes of Cu-doped ZnO nanosheets, based on the existence of Cu-rich layer beneath Cu-doped ZnO nanosheets.展开更多
基金supported by the National Basic Research Program of China (Grant No. 2012CB932702)the National High Technology Research and Development Program of China (Grant No. 2013AA031601)+2 种基金the National Natural Science Foundation of China (Grant Nos. 50831002,51071022,11174031,and 51271020)PCSIRT,Beijing Nova Program (Grant No. 2011031)the Fundamental Research Funds for the Central Universities
文摘Zn0.99Cu0.01O films were studied experimentally and theoretically. The films were prepared by pulsed-laser deposition on Pt（111）/Ti/SiO2/Si substrates under various oxygen pressures to investigate the growth-dependence of the ferromagnetic properties. The structural, magnetic, and optical properties were studied, and it was found that all the samples possess a typical wurtzite structure, and that the films exhibit room-temperature ferromagnetism. The sample deposited at 600 ℃ and an oxygen pressure of 10 Pa showed a large saturation magnetization of 0.83 μB/Cu. The enhanced ferromagnetism in the （Cu, Li）-codoped ZnO is attributable to the existence of Zn vacancies （Vzn）, as shown by first-principles calcu- lations. The photoluminescence analysis demonstrated the existence of Vzn in both Zn0.99Cu0.01 O and （Cu, Li）-codoped ZnO thin films, and this plays an important role in the increase of ferromagnetism, according to the results of first-principles calculations.
基金Project supported by the Universiti Teknologi Malaysia(UTM)(Grant No.R.J1300000.7809.4F626)RMC for postdoctoral grants
文摘Zn（1-x）Cux O（x=0.00, 0.01, 0.03, and 0.05） nanoparticles are synthesized via the sol-gel technique using gelatin and nitrate precursors. The impact of copper concentration on the structural, optical, and antibacterial properties of these nanoparticles is demonstrated. Powder x-ray diffraction investigations have illustrated the organized Cu doping into ZnO nanoparticles up to Cu concentration of 5%（x = 0.05）. However, the peak corresponding to CuO for x= 0.01 is not distinguishable. The images of field emission scanning electron microscopy demonstrate the existence of a nearly spherical shape with a size in the range of 30–52 nm. Doping Cu creates the Cu–O–Zn on the surface and results in a decrease in the crystallite size. Photoluminescence and absorption spectra display that doping Cu causes an increment in the energy band gap. The antibacterial activities of the nanoparticles are examined against Escherichia coli（Gram negative bacteria）cultures using optical density at 600 nm and a comparison of the size of inhibition zone diameter. It is found that both pure and doped ZnO nanoparticles indicate appropriate antibacterial activity which rises with Cu doping.
基金supported by the National Natural Science Foundation of China (Grant No. 50802041)the National Key Projects for Basic Research of China (Grant No. 2010CB923404)Southeast University
文摘Zn0.98Cu0.020 powders are prepared by the sol-gel method. A small number of CuO impurity phases are observed by the x-ray diffraction, indicating the solubility of Cu in ZnO is less than 2 at.%. The Zn0.98Cu0.020 powders exhibit diamagnetism at 300 K and paramagnetism at 5 K. After subtracting the diamagnetic contribution of ZnO bulk and the paramagnetic contribution of defects, Cu ions exhibit weak paramagnetism. By codoping Cu with Co or Mn in ZnO, only paramagnetism is observed at room temperature.
基金Project supported by the Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education at Lanzhou University of China (Grant No. LZUMMM2012003)the Chunhui Project of the Ministry of Education of China (Grant No. Z2008-1-62023)the Fundamental Research Funds for the Central Universities of Ministry of Education of China (Grant No. 860452)
文摘Room-temperature photoluminescence and optical transmittance spectroscopy of Co-doped（1×1014,5×1016,and 1×1017cm-2） and Cu-doped（5×1016cm-2） ZnO wafers irradiated by D-D neutrons（fluence of 2.9×1010 cm-2） have been investigated.After irradiation,the Co or Cu metal and oxide clusters in doped ZnO wafers are dissolved,and the wu¨rtzite structure of ZnO substrate for each sample remains unchanged and keeps in high c-axis preferential orientation.The degree of irradiation-induced crystal disorder reflected from the absorption band tail parameter（E0） is far greater for doped ZnO than the undoped one.Under the same doping concentration,the Cu-doped ZnO wafer has much higher irradiation-induced disorder than the Co-doped one.Photoluminescence measurements indicate that the introduction rate of both the zinc vacancy and the zinc interstitial is much higher for the doped ZnO wafer with a high doping level than the undoped one.In addition,both crystal lattice distortion and defect complexes are suggested to be formed in doped ZnO wafers.Consequently,the Co-or Cu-doped ZnO wafer（especially with a high doping level） exhibits very low radiation hardness compared with the undoped one,and the Cu-doped ZnO wafer is much less radiation-hard than the Co-doped one.
基金supported by the National Natural Science Foundation of China(Grant Nos.51031004 and 51272078)the Natural Science Foundation of Guangdong,China(Grant No.S2012010008124)+3 种基金the National Basic Research Program of China(Grant No.2015CB921202)the Project for Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme(2014)International Science & Technology Cooperation Platform Program of Guangzhou,China(Grant No.2014J4500016)the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(Grant No.IRT1243)
文摘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-.
文摘Nanocrystalline Zn1_xCuxO （x = 0, 0.02, 0.04, 0.06, 0.08） samples were synthesized by a novel auto-combustion method using glycine as the fuel material. The structural, optical and magnetic properties of the samples were characterized using XRD, SEM, photoluminescence （PL） and electron paramagnetic resonance （EPR） spectro- scopies. The XRD spectra of samples reveal the hexagonal wurtzite structures of ZnO. As the copper content increases, a diffraction peak at 28 = 39° corresponding to secondary phase of CuO （[111] crystalline face） appears when x≤ 6 mol.%. PL spectra of the samples show a strong ultraviolet （UV） emission and defect related visible emissions. Cu-doping in ZnO can effectively adjust the energy level in ZnO, which leads to red shift in the emission peak position in UV region. The EPR spectra of Cu-doped ZnO nanoparticles show a distinct and broad signal at room temperature, suggesting that it may be attributed to the exchange interactions within Cu2＋ ions.
基金financially supported by the Henan University of Science and Technology through a grant of Postgraduate Innovation Fund(No.CXJJ-Z015)the Foundation and Advanced Technology Fund of Henan Science and Technology Department(No.11230041002)the Program for Changjiang Scholars and Innovative Research Team in University(No.IRT1234)
文摘The synthesis of Cu-doped ZnO nanosheets at room temperature was reported in our previous paper. The effects of annealing temperature on Cu-doped ZnO nanosheets were studied in this paper. Cu-doped ZnO nanosheets were annealed at 200-500℃ in air. The annealed specimens were characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD） and transmission electron microscopy （TEM）. The results show that Cu concentration in Cu-doped ZnO nanosheets reduced with increasing annealing temperature. When annealing temperature was lower than Zn melting point （410℃）, the morphologies of the Cu-doped ZnO nanosheets remained nearly the same as that before annealing. However, when the annealing temperature was over Zn melting point, Cu-doped ZnO nanosheets changed to nanowires, wormlike nanosheets or did not change. The change of Cu concentration in Cu-doped ZnO nanosheets is explained by oxidation thermodynamics. A physical model is suggested to explain the morphology changes of Cu-doped ZnO nanosheets, based on the existence of Cu-rich layer beneath Cu-doped ZnO nanosheets.
