Critical effect of reaction pH on the microstructural, optical and electrical behavior of ZnO/CuO hetero-structured nanocomposite films (original) (raw)
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Acta Physica Polonica A, 2014
In the present work, ZnO/CuO composite nanostructures have been grown on uorine doped tin oxide coated glass substrate by aqueous chemical growth method. To observe the eect of post growth annealing (500 • C, 1 min) on the structural properties of ZnO nanorods scanning electron microscope and X-ray diraction techniques have been utilized. SEM images of post growth annealed (post growth annealed) sample reveal that the average diameter of ZnO NRs has considerably increased in comparison with as grown sample. Moreover after post growth annealing the ZnO NRs showed more clearly hexagonal wurtzite structure. Beside this the NRs are also uniform and well aligned with a high aspect ratio of ∼10. In XRD pattern the strongly intense (002) peak of the post growth annealing sample suggest that the crystal quality of the NRs have also been improved signicantly. Since the structural improvement have a signicant impact on charge transport properties as well, therefore the eect of post growth annealed has also been investigated by the electrical characterization of ZnO/CuO based heterojunction. The current-voltage measurements of the post growth annealed sample showed improvement in the current in comparison with as grown sample. The impedance study has also conrmed that the post growth annealed has inuence on the electrical properties. The presented post growth annealed heterojunction of ZnO/CuO may have space in applications like sensors and oxide based diodes in the devices fabrication.
Journal of Nanoelectronics and Optoelectronics, 2014
The study of the optical properties of zinc oxide (ZnO) nanorods and its composite nanostructures is an appealing issue in order to have highly efficient optoelectronic devices in the future. Zinc oxide, copper oxide (CuO) and their composite nanostructures were grown by the hydrothermal growth technique. The structural properties of the grown ZnO, CuO and their composite NSs were investigated by scanning electron microscopy and X-ray diffraction techniques. UV-visible spectroscopy, Cathodoluminescence and photoluminescence techniques were used for the study of optical properties of the as synthesized nanomaterials. X-ray photoelectron spectroscopy was used to measure the valence band offset of the CuO/ZnO composite nanostructures. Cathodoluminescence study of pure ZnO nanorods showed more insight for lateral luminescence compared to the top surface of the nanorods which opened a novel investigation in the area of optical properties of ZnO nanomaterial. While the room temperature cathodoluminescence spectra of CuO/ZnO composite nanostructures have demonstrated excellent luminescence in the UV region compared to the cathodoluminescence spectra observed at 4 K. The measured values for valence band offset and conduction band offset are found to be 2.83 eV and 0.73 eV, respectively for the prepared CuO/ZnO composite nanostructures. It was observed that CuO/ZnO composite nanostructures have type-II band alignment. The conclusion from both the cathodoluminescence and the photoluminescence studies showed that the luminescence in the visible region is only originated from the ZnO nanomaterial and that the CuO absorbs this visible emission as it covers the ZnO. This provides evidence suggesting that the use of CuO/ZnO in the fabrication of LEDs in the visible range is not appropriate.
Influence of Cu doping on the structural, electrical and optical properties of ZnO
Pure and Cu-doped zinc oxide (ZnO) nanoparticles were prepared using a chemical method. The dopant concentration (Cu/Zn in atomic percentage (wt%)) is varied from 0 to 3 wt%. Structural characterization of the samples performed using X-ray diffraction (XRD) confirmed that all the nanoparticles of zinc oxide are having polycrystalline nature. Morphological studies were conducted using field emission scanning electron microscopy (FESEM) to confirm the grain size and texture. Electrical measurements showed that the AC conductivity initially decreases and then rises with increasing Cu concentration. The UV–Vis studies showed absorbance peaks in the 200– 800 nm region. It is found that the absorbance does not significantly change with doping. This fact is further confirmed from the band-gap calculations using the reflectance graphs. When analysed in terms of Burstein–Moss shift, an increase of band gap from 3.42 to 3.54 eV with increasing Cu concentration is observed. In the photoluminescence (PL) studies a red-shift is observed with increasing dopant concentration.
Compositional, Structural and Optical Properties of Cu2+ Doped ZnO Nanocrystalline Thin Films
Pure ZnO and copper incorporated ZnO thin films with various Cu2+ concentrations have been prepared using a new chemical bath deposition route on glass substrate immersed in ammonium solution bath, in which zinc acetate heptahydrate acts as a complexing agent and urea acts as a source of oxide ions. The chemical composition of films was determined by energy dispersive X-ray analyzer (EDAX). The prepared films are very close to ZnO stoichiometry and no impurity compounds such as Zn(OH)2 or CuO species were observed. The pure and Cu doped ZnO structures were characterized by X-ray diffraction (XRD), and transmission electron microscopy (TEM). The XRD results revealed that prepared nanocrystalline films have wrutzite structure and the unit cell volume increased with increasing Cu concentration. Optical properties of the synthesized nanocrystalline were investigated by UV-Vis. spectroscopy and room temperature photoluminescence (PL) spectroscopy. It is seen that the optical band gap increases when the ZnO is doped with copper. Room temperature PL spectra of these structures showed a strong UV emission peak and a relative broad emission peak, and the UV emission peak of the doped ZnO nanocrystalline films was red-shifted with respect to that of the pure ZnO nanocrystalline film.
Effects on Structural Morphological and Optical Properties Pure and CuO/ZnO Nanocomposite
Trends in Sciences
In the present work, synthesis of CuO, ZnO and CuO/ZnO Nonocomposites and their properties have been investigated. CuO, ZnO and CuO/ZnO NC were synthesized using the co-precipitation method. The nanocomposite materials were structural, morphological and optical properties characterized by X-ray diffraction (XRD), Field Emission Scanning Electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), UV-Vis Spectroscopy. The results of the XRD analysis exhibited that the pure CuO, ZnO and CuO/ZnO NC has a nanometer size with an average of 15.19 nm. The UV-vis analysis showed that the CuO, ZnO and CuO/ZnO NC has a band-gap of 3.31 and 2.35 eV. FTIR investigation revealed that the vibration of ZnO was observed at 561 cm-1 whereas CuO was at 602 cm-1 and composites 612 cm-1. The FESEM-EDX analysis revealed that the ZnO has a hexagonal structure whereas the CuO has a monoclinic structure. HIGHLIGHTS Present investigation deals with...
Characterization and Doping Effect of Cu-Doped ZnO Films
Journal of Materials Science and Engineering A, 2020
Cu (copper)-doped ZnO (zinc oxide) was synthesized using Cu(NO 3) 2 •3H 2 O (copper (II) nitrate) and Zn(NO 3) 2 •6H 2 O (zinc nitrate) by chemical co-precipitation method. The weight percentages of dopant in solution were Cu (2, 3, and 5 wt %). Cu-doped ZnO thin films were prepared on p-Si (100) substrate by screen printing method. Cu-doped ZnO/Si films were annealed at different temperatures from 300 to 700 °C. In this study, Cu-doped ZnO structures were prepared by a simple precipitation technique, and characterized by various techniques such as XRD (X-ray diffraction) and SEM (scanning electron microscope). The electrical properties of Cu-doped ZnO/Si were measured. It has found that Cu-doped ZnO/Si films can be used as optoelectronic devices.
Impedance and electrical properties of Cu doped ZnO thin films
2017
Cu doped transparent ZnO thin films were spin coated on conductive glass substrates. The samples were subsequently annealed in air for 1 hour at 500 0C in order to form the phase of ZnO. ZnO samples were doped with different Cu molar percentages up to 5%. The impedance and photovoltaic properties of sample were measured. Photocurrent and photovoltage of doped and undoped samples were measured in KI/I2 electrolyte. Adding a trace amount of Cu improved the conducting properties of ZnO samples without changing other basic properties of ZnO. The photocurrent gradually increases with the doping concentration due to the high conducting properties of Cu. Investigation was carried out only up to the doping concentration of 5%, because higher doping concentrations may significantly influence the other properties of ZnO such as transparence of the film. Impedance of samples was determined by fitting the data to an equivalent circuit. The impedance reaches the maximum value at Cu concentration...
Journal of Materials Chemistry, 2012
Using ZnO seed layers, an efficient approach for enhancing the heterointerface quality of electrodeposited ZnO-Cu 2 O solar cells is devised. We introduce a sputtered ZnO seed layer followed by the sequential electrodeposition of ZnO and Cu 2 O films. The seed layer is employed to control the growth and crystallinity and to augment the surface area of the electrodeposited ZnO films, thereby tuning the quality of the ZnO-Cu 2 O heterointerface. Additionally, the seed layer also assists in forming high quality ZnO films, with no pin-holes, in a high pH electrolyte solution. X-ray electron diffraction patterns, scanning electron and atomic force microscopy images, as well as photovoltaic measurements, clearly demonstrate that the incorporation of certain seed layers results in the alteration of the heterointerface quality, a change in the heterojunction area and the crystallinity of the films near the junction, which influence the current density of photovoltaic devices.
On the sol pH and the structural, optical and electrical properties of ZnO thin films
Superlattices and Microstructures, 2016
Zinc oxide thin films were prepared by the sol-gel method and deposed on glass substrate using spin coating technique. The variation of the structural, optical and electrical properties with various pH values is investigated. pH values of the sol were adjusted with glacial acetic acid and ammonia. X-ray diffraction analysis showed that the films with alkaline sol are crystallized while those with acidic sol are amorphous. High values of texture coefficient and a high diffraction intensity of the (002) peak, ensuring better growth along c-axis, were obtained for an optimal pH value of 9.5. The crystallite size of the obtained films strongly depends on the sol pH. Scanning Electron Microscopy (SEM) images confirm that the morphology and grain size of the films are affected significantly by pH. The optical transmission was recorded to analyze the optical properties of the studied films. It was found that the optical gap increased with pH. The electrical properties were measured by Hall-effect and reveal an increase of the resistivity when the sol pH increases. A minimum residual intrinsic electrons density suitable for p-type ZnO was reached.
Journal of Nepal Physical Society
The most common materials used to create electrical and optoelectronic devices for a variety of applications including transistor, sensor and detector are semiconductor nanostructures. Combining the nanostructures can result semiconductor homostructure and heterostructure. The homojunction of ZnO/FTO and heterojunction of CuO/ZnO/FTO coated glass substrate are formed using spray pyrolysis technique. The optical band gap for the FTO, ZnO, ZnO/FTO and CuO/ZnO/FTO films calculated using data from UV-visible spectroscopy are 3.629 eV, 3.236 eV, 3.113 eV and 1.456 eV respectively. The observed ohmic behavior of ZnO/FTO homojunction is due to the close band gap of FTO (i.e. Eg = 3.629 eV) and ZnO (Eg = 3.236 eV) whereas the non-ohmic behavior of CuO/ZnO/FTO heterojunction is due to the significant different in band gap energy of CuO (i.e. Eg = 1.456 eV) and ZnO (Eg = 3.236 eV). The photocurrent for ZnO/FTO homojunction increases from 232 μA to 350 μA for visible light illumination and fro...