M. Highasiata

Abstract: The paper deals with study of Sb Al co-doped ZnO nanowires synthesized using Nanoparticle Assisted Pulsed Laser Deposition (NAPLD). The nanowires were synthesized by using ZnO:Al as target and Sb coated Si as substrate. At a growth temperature of 750 °C, random oriented high density nanowires with a diameter of about 1 μm and a length up to a few tens of micro meters were synthesized. The samples were annealed at 450, 550 and 650 °C. The Sb Al co-doped ZnO nanowires annealed at 650 °C showed a significant change in lattice constant of 0.06° from XRD and widening of lattice fringe spacing of 0.56 nm from TEM. From the XPS analysis, a peak at 539.5 eV a near binding energy of Sb O bond and peak at 76.2 eV corresponding to Al O bonds confirms the penetration of oxygen. The suppression of A 1 T modes and E 1 (L0) modes from Raman spectroscopy confirms the depletion of oxygen vacancies. Thus resulting in a strong improvement in UV emission and reduction in visible emission as observed from room temperature PL.

Abstract: The paper deals with synthesis of Sb and Sb–Al co-doped ZnO nanowires using nanoparticle assisted pulsed laser deposition (NAPLD) by considering Sb as a catalyst. The mechanism of the growth initiation of nanostructures from the Sb droplets is analyzed at varying growth temperature. Nanowires and nanosheets of different orientation were synthesized. With ZnO:Al target and Sb coated Si as substrates, at a growth temperature of 750 °C, random oriented high density nanowires with a diameter of about 1 μm and a length up to a few tens of micrometer were synthesized. The suppression of A1T modes and E1(L0) modes from Raman spectroscopy confirming that depletion of oxygen vacancies. XPS analysis confirming that the Sb would substitute for Zn(Sbzn) instead of oxygen Al–O bonds, leading to excess of oxygen, neutralizing the oxygen vacancies. The Sb–Al co-doped nanowires annealed at 650 °C showed a strong UV emission and reduction in visible emission as compared to the Sb–Al co-doped nanowires annealed at 450 °C. This confirms that the Sb–Al co-doped posses high stoichiometric nature, good structural and optical properties. To investigate the p-type conductivity of the Sb–Al co-doped nanowires, a homo p–n junction was prepared by synthesizing Sb–Al co-doped ZnO nanowires on the pure ZnO surface. The I–V characteristics of the homo P–N junction were investigated and a rectifying behavior was observed confirming the formation of p-type. Hence the Sb mono-doped and co-doped ZnO nanowires synthesized by using Sb as catalyst posses good structural and optical properties with good crystallization quality and high stoichiometry nature, hence it is highly suitable for light emitting device applications.

Abstract: This research highly focuses towards influence of different paprmaters in development of Sb doped ZnO nanostructures using Nano Particle Assisted Pulsed Laser Deposition by using Sb coated substrate.different types of nanostructures were synthesized with vartion in growth temperature. Nano wires generated from Sb coated silicon substrate posses a sharp UV emission from room temperature PL. vertically aligned ZnO nanowires were grown on different ZnO buffer layer thickness ranging from 100 to 1600 nm. With increase in buffer layer thickness a strong UV emission with improved structural properties are observed, which are highly suitable for optoelectronic device application.

Abstract: Pure hexagonal wurtzite ZnO nanostructure was successfully synthesized by chemical vapor deposition (CVD) and RF-magnetron sputtering without using any catalysts. In the two-step process, high-quality multi-oriented ZnO nanorods were obtained. Multi-oriented spear-like ZnO rods were pre-deposited on the SiO 2 /Si(1 0 0) substrate by CVD at 700 °C followed by RF sputtering of the ZnO nanostructure. The synthesized ZnO nanostructures were characterized by X-ray diffraction, field emission scanning electron microscopy, and photoluminescence (PL). The results show that the RF sputtering of the ZnO nanostructure, which was coated with a ZnO film produced by CVD, might have promoted the uniformity and crystalline quality of the multi-oriented spear-like ZnO film. The PL spectra revealed a sharp and dominant peak located at approximately 382 nm with a UV-to-visible PL intensity ratio ( I UV / I VS ) of 42 for the sample that was produced by the two-step process. The growth mechanism of the multi-oriented spear-like ZnO nanorods was investigated.

Abstract: In this article, an efficient synthesis of histidine-capped ZnO nanoparticles was carried out in absolute ethanol by using solvothermal technique. The synthesized nanoparticles were further characterized by using different techniques such as powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), Fourier transfer infrared (FTIR), UV-visible spectroscopy, thermal analysis (TG/DTG/DTA) and photoluminescence spectroscopy. The XRD measurement reveals that the prepared nanoparticles have hexagonal wurtzite structure. From XRD data, the average crystalline size is calculated to be 22 nm according to half width of (1 0 1) diffraction peak using Debye-Scherrer formula. Moreover, the antibacterial activities of nanoparticles sample have been performed under standard method. The antibacterial activities of histidine-capped zinc oxide nanoparticles are tested against human bacterial pathogen such as Staphylococcus aureus, Escherichia coli, Klebsiella sp., Enterococcus faecalis and Pseudomonas aeruginosa by using agar well diffusion method. Besides, antibacterial activities of ZnO nanoparticles (20 to 60 μg) are compared with four well-known antibiotics viz., Amikacin (30 mcg), Ciprofloxacin (5 mcg), Gentamicin (5 mcg) and Norfloxacin (10 mcg). From antibacterial studies, it has been concluded that if the concentration of histidine-capped ZnO nanoparticles increases, then the antibacterial activities also increase.

Abstract: ZnO is one of the most important functional materials with a wide direct band gap, large exciton binding energy, and facile growth of high quality nanostructures, which make it very promising for various optoelectronic applications, especially in light-emitting diodes, piezotronics and nanoelectronics. However, ZnO suffers from the doping asymmetry problem, and p-type doping is not stable, which is major hurdle for its application in optoelectronics. Co-doping, which is defined as doping acceptor with other impurities simultaneously, was proposed and attempted to address the p-type doping problem by enhancing the solubility and reducing the ionization energy of acceptor dopants. During the past two decades, extensive studies on co-doping have shown positive effects on improving the p-type conductivity of ZnO. The success was made mainly in ZnO films and nanowires. In this article, we provide an overview of the experimental efforts for growing p-type ZnO nanocrystalline films by the co-doping method, which are mainly classified as acceptor-donor co-doping, dual-acceptor co-doping, acceptor-hydrogen co-doping, and acceptor-isovalence co-doping. In addition, a few works on co-doped p-type ZnO nanowires are also summarized. Finally, we discuss the remaining problems of p-type ZnO by co-doping.

Abstract: The spin coated ZnO thin films were synthesized and tested for O 2 and NO 2 gas detection. It exhibited an increase in resistance i.e. n-type behavior for O 2 exposure (5–20%) and decrease in resistance i.e. p-type behavior for NO 2 (2–40 ppm) exposure at operating temperatures of 250 °C and 300 °C in N 2 atmosphere (0.4 ± 0.03 mbar). The origin of this aberrant behavior for NO 2 exposure was attributed to the participation of defects in NO 2 sensing characteristics in light of the data obtained from photoluminescence and Raman spectroscopy studies demonstrating the unique defect morphology of ZnO thin film. The underlying mechanism is discussed on the basis of conclusions drawn from characterization techniques and subsisting knowledge in the literature. The NO 2 gas sensing is explained in terms of two competing mechanisms: one is change in charge carrier density on gas exposure as explained by surface depletion model and another is due participation of defects (oxygen vacancies) in gas sensing characteristics.

Abstract: Sb-doped ZnO thin films with different values of Sb content (from 0 to 11 at%) are deposited by the sol–gel dip-coating method under different sol concentrations The effects of Sb-doping content, sol concentration, and annealing ambient on the structural, optical, and electrical properties of ZnO films are investigated The results of the X-ray diffraction and ultraviolet-visible spectroscopy (UV-VIS) spectrophotometer indicate that each of all the films retains the wurtzite ZnO structure and possesses a preferred orientation along the c axis, with high transmittance (> 90%) in the visible range The Hall effect measurements show that the vacuum annealed thin films synthesized in the sol concentration of 075 mol/L each have an adjustable n-type electrical conductivity by varying Sb-doping density, and the photoluminescence (PL) spectra revealed that the defect emission (around 450 nm) is predominant However, the thin films prepared by the sol with a concentration of 025 mol/L, despite their poor conductivity, have priority in ultraviolet emission, and the PL peak position shows first a blue-shift and then a red-shift with the increase of the Sb doping content