Effect of Post Growth Annealing on the Structural and Electrical Properties of ZnO/CuO Composite Nanostructures (original) (raw)
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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.
Zinc oxide nanorods was synthesized by using hydrothermal growth due to simplicity and involve low temperature processing that is 93 0 C. Low temperature processing is very essential for ZnO nanorod synthesis because defect on developing nano-device can be avoided. Development of nanodevice with minimal defect is essential to ensure that the performances of the nano device is optimum for sensing biomolecular substances. Zinc oxide has become the most remarkable choice among other metal oxides semiconductor due to many criteria such as economical cost, unique physical and electrical properties and biocompatible. Initially, ZnO thin films was prepared by using sol gel method. The ZnO seed solution was prepared using conventional sol-gel route. Zinc oxide solution was prepared in two different solvents which are isopropanol (IPA) and methanol (MeOH) in order to investigate the influence of solvent to the quality of ZnO nanorods. MEA, the sol stabilizer was added to the solution for the following 2 hours. Aluminum IDE electrode was deposited on the silicon wafer sample <100> using traditional wet etching method. Positive photoresist (PR) was coated on the silicon wafer and followed with soft back for 90 seconds. IDE pattern transfer was done by exposing UV light (365nm) onto the PR for 10 seconds. After that, developing and etching process occurred for pattern transfer the IDE electrode onto the silicon wafer. The prepared seed solution was coated on silicon wafer by using speed coating method. Some of the coated samples underwent annealing process at temperature 200 0 C for 2 hours. The annealed and non-annealed sample undergoes hydrothermal growth method to synthesize ZnO nanorods. The synthesized nanorods underwent I-V test and capacitances to investigate the electrical behavior of ZnO nanorods. The annealed ZnO nanorods provided higher current, which was 900μA, as compared the non-annealed ZnO nanorods which was only 55 μA.
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...
• Cu-doped ZnO (Zn 1-x Cu x O) nano-ceramics were prepared by ball-milling of the CuO and ZnO powders. • Up to 3 at% of Cu could be doped in ZnO via ball milling, beyond which Cu precipitates as CuO during calcination. • The ac conductivity values decrease by Cu doping in ZnO, making it a better dielectric material. • Cu doping in ZnO via ball milling is cost effective and scalable to industrial level. Nanocrystalline Cu doped ZnO (Zn 1-x Cu x O, x = 0, 0.01, 0.02, 0.03 and 0.04) samples were synthesized by high energy ball milling technique (HEBM). The strain developed during ball milling and incorporation of Cu into the Zn-site in ZnO lattice is depicted as broadening of the full width at half maximum (FWHM) of the XRD. The X-ray diffraction peak-widths (FWHM) increases with increase in Cu-concentration. Furthermore, the mechanical impact and the heat produced during ball milling helps in the formation of aggregates. The size of these aggregates was observed to increase with Cu-concentration. Upon calcination, these aggregated structures form particle, resulting in bigger particles for higher concentration of Cu. The XRD results confirm that up to ∼3 at% of Cu can be doped in ZnO lattice, beyond which CuO precipitates. The impedance spectroscopy and the ac-conductivity results confirm the improvement in dielectric properties of ZnO by Cu doping. The decrease in magnitude of Z′ on increase in temperature confirms the negative temperature coefficient of resistance (NTCR) behaviour of the samples. The ac conductivity of ZnO decreases with Cu doping and follows the correlated barrier hopping (CBH) model in the investigated temperature and frequency range.
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.
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 Nanoscience and Nanotechnology, 2009
In the present study, results on the influence of interchanging Se and Te as major content (80%) on the structural, morphological and optical properties of copper doped ternary chalcogenide thin films Se 80 Te 10 Cu 10 (Se-rich) and Te 80 Se 10 Cu 10 (Te-rich) are reported. The films have been synthesized on glass substrates by thermal evaporation method. Bulk samples used for synthesizing the thin films have been prepared using melt quenching technique. The films have been characterized by XRD, FESEM, UV-Visible-NIR spectroscopy and Photoluminescence (PL) spectroscopy. Structural studies show amorphous and polycrystalline nature of the Se-rich and Te-rich films respectively. Surface morphological images show scattered grains in the Se-rich film whereas densely packed and similar sized grains are found in the Te-rich film. Transmission is much higher for the Se-rich film in the near infrared region. PL spectra recorded at two different excitation wavelengths-380 nm and 450 nminvariably show green emission for both the films. Yellow emission is also found at 450 nm excitation wavelength.
Morphological Variations and Structural Properties of ZnO nanostructures Grown by Rapid Thermal CVD
Journal of Nanoscience and Nanotechnology, 2011
Various nanostructures of ZnO such as nanowires, sea urchin like and nano needles were grown using rapid thermal chemical vapor deposition technique (RTCVD), in oxygen ambient. For the growth of such structures, oxygen pressure was kept as 0.1 Torr whereas the chamber base pressure was 10 −5 Torr. The growth temperature was varied from 600 C to 850 C, which resulted in morphological variations. X-ray diffraction measurement revealed the hexagonal wurtzite structure of ZnO preferably oriented in [001] direction, which was further confirmed by high-resolution transmission electron microscopic (HRTEM) observations. X-ray photoelectron spectroscopy (XPS) analysis suggests the presence of Zn 2p and O 1s. Raman E 2 high peaks at ∼434 cm −1 has the highest intensity compared to other modes supports XRD results. Presence of low E 2 peaks at ∼330 cm −1 indicates defects and oxygen vacancies.
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.