Co-DOPED ZnO NANOWIRES GROWN BY VAPOR-LIQUID-SOLID METHOD: STRUCTURAL, OPTICAL AND MAGNETIC STUDIES (original) (raw)
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We report on the high-pressure pulsed laser deposition growth of zinc oxide nanowires containing about 0.2 at.% Co and 0.5 at.% Mn by NiO and Au catalyst. Scanning electron microscopy and X-ray diffraction measurements revealed arrays of parallel-standing nanowires with hexagonal cross section and uniform in-plane epitaxial relations without rotational domains. Elemental analysis was carried out using particle induced X-ray emission and Q-band electron spin resonance. The valence of the incorporated Mn was determined to be 2+. Atomic and magnetic force microscopy measurements indicate that Mn is incorporated preferentially at the nanowire boundaries.
Journal of Crystal Growth, 2013
Mn-doped ZnO nanowires were successfully synthesized by using the low temperature aqueous chemical growth (ACG) method. Field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy have been used to characterize the grown Zn 1−x Mn x O. The FESEM and the XRD measurements revealed that the grown of Mn-doped ZnO had wurtzite structure and the lattice parameters and the size of the crystal changed according to the change of concentration of the dopant. The chemical composition and charge states of the Mn ions doped in the ZnO nanowires was analyzed by the EDX and the XPS, respectively, indicated that the Mn ions is incorporated onto zinc sites in the ZnO nanowires. PL spectroscoCpy shows a strong ultraviolet (UV) emission peak at 378 nm (3.27 eV) from the Mn-doped ZnO nanowires, which is shifted 6 nm to the lower wavelength compared to ZnO nanowires grown by the same ACG method. The unique feature of our samples were the simple low temperature growth method which provides no clustering and the as-synthesized Mn-doped ZnO nanowires have shown good crystal quality. This capability to fabricate Mn-doped ZnO nanowires is of potential to develop new spintronic, photonic and sensor devices fabrication on any substrates.
Synthesis and magnetic properties of Mn doped ZnO nanowires
2007
Mn doped ZnO nanowires have been synthesized using a simple autocombustion method. The as-synthesized Mn doped ZnO nanowires were characterized by X-ray diffraction and transmission electron microscopy. An increase in the hexagonal lattice parameters of ZnO is observed on increasing the Mn concentration. Optical absorption studies show an increment in the band gap with increasing Mn content, and also give evidence for the presence of Mn2+ ions in tetrahedral sites. All Zn1−xMnxO (0≤x≤0.250≤x≤0.25) samples are paramagnetic at room temperature. However, a large increase in the magnetization is observed below 50 K. This behavior, along with the negative value of the Weiss constant obtained from the linear fit to the susceptibility data below room temperature, indicate ferrimagnetic behavior. The origin of ferrimagnetism is likely to be either the intrinsic characteristics of the Mn doped samples, or due to some spinel-type impurity phases present in the samples that could not be detected.
CVD PREPARED Mn-DOPED ZnO NANOWIRES
Mn-doped ZnO nanowires prepared by chemical vapor deposition (CVD) were obtained in the temperature range of 450-500 o C. X-ray diffraction patterns, SEM and TEM images indicate that crystals with a hexagonal structure grow along the c axis. At low Mn-doped concentrations, photoluminescence (PL) and Raman scattering (RS) spectra are almost independent of the Mn doping. However, the increase in concentration of Mn above 1.6 at% weakens significantly the PL signal and the RS-lines intensity in the low wavenumber range of 300-480 cm-1 , and concurrently increases the RS-lines intensity in the higher wavenumber range of 480-700 cm-1. Magnetic measurements determined the Curie temperature of Mn-doped ZnO nanowire to be about 37 K.
Electrical and Magnetic Properties of Doped ZnO Nanowires
MRS Proceedings, 2006
ZnO nanowires doped with Mn, Fe, Sn, and Li during the thermal growth following direct chemical synthesis were investigated using electric and magnetic measurements. Currentvoltage characteristics of individual nanowires configured as a two-terminal device with Al electrodes show apparent rectify behavior indicating the Schottky-like barrier formation and resistivity being less 3 Ω · cm. Reproducible resistance modulation by a dc voltage at room temperature is observed. Magnetic susceptibility of the doped nanowires as a function of temperature demonstrates Curie-Weiss behavior. Magnetization versus field curves show hysteresis with the coercive field of about 200 Oe. The spatially-resolved magnetic force measurements of individual nanowires revealed the magnetic domain structure. The domains align perpendicular to c-axis and can be polarized in the external magnetic field.
Journal of Magnetism and Magnetic Materials, 2024
In the search for a diluted magnetic semiconductor (DMS) for spintronics devices, Zn1-xCoxO (x =0, 0.020, 0.035, 0.050, and 0.065) nanoparticles (NPs) were synthesized using a simple and cost-effective co-precipitation technique. To demonstrate the advantages of Co-doping, the morphological, microstructure, optical, and magnetic properties of the Co-doped ZnO NPs were extensively investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), selected area electron diffraction (SAED), Raman spectroscopy, ultraviolet–visible (UV–vis.) spectroscopy, and vibrating sample magnetometer (VSM) techniques. The synthesized NPs exhibited a hexagonal wurtzite structure. Their lattice parameters were found to decrease with increasing Co-doped wt.%, confirming the incorporation of Co2+in ZnO. The solid solution limit of Co-ZnO NPs was found to be Zn0.965Co0.035O. The crystallite sizes of the NPs were found to vary from 38.36 to 39.68 nm. Pure ZnO formed both the nanospheres (NSs) and nanorods (NRs), but Co-doped ZnO generated NRs only. The narrowest NR, with a diameter of 94 nm, was obtained for the Zn0.965Co0.035O. With a ‘Blue shift’ , the band gap energies were found to increase from 3.34 to 3.61 eV. The ZnO showed diamagnetic behavior whereas all the Co-doped NRs showed room temperature ferromagnetic (RTFM) properties. The highest magnetization values (Ms) 5.07 ×10-2 emu/g and (µB/Co2+) 14.93 ×10-3 were observed for Zn0.965Co0.035O NRs, and these values are several times higher than many previously reported values. The origin of the ferromagnetism was found to be an intrinsic property of the Co-doped ZnO NRs. The study successfully synthesized Co-doped ZnO DMS, which could be used for spintronic-based photoelectronic and ferromagnetic devices.
Advanced Materials, 2008
The wide-gap semiconductor ZnO is a potential candidate for many applications, including gas sensing, varistors, lightemitting devices, and solar cells. The nanostructure of ZnO has been extensively studied. ZnO nanowires have been found to be promising for nanometer-scale optoelectronics, electronic devices, and biotechnology. Many methods have been used to fabricate ZnO nanowires, such as high-pressure pulse laser deposition (PLD), vaporliquid-solid methods, chemical vapor deposition, and templateassisted methods. It is known anodic aluminum oxide (AAO) templates are widely used for the preparation of nanowires. However, there have been only a few reports on the fabrication of ZnO nanowires via electro-deposition and oxidation of Zn nanowires into AAO templates, probably because of the limitation imposed by the formation of ZnAlO 3 .
Journal of Alloys and Compounds, 2009
Well-crystallized high-aspect-ratio antimony (Sb)-doped ZnO nanowires have been successfully synthesized on Si(1 0 0) substrates in a large-quantity via simple thermal evaporation process by using metallic zinc and Sb powders in the presence of oxygen. It is observed from the detailed structural characterizations that the grown nanowires are well-crystallized with the wurtzite hexagonal phase and preferentially grown along the [0 0 0 1] direction. It was clearly seen from the high-resolution TEM images that the Sb-atoms are successfully doped into the lattices of ZnO nanowires. The room-temperature photoluminescence (PL) spectrum exhibited a broad band in the visible region with a suppressed UV emission, indicating the presence of structural defects due to insertion of Sb-atoms in the lattices of as-grown nanowires. Due to the enhancement of green emission in the formed nanowires, these structures show great interest for typical applications of ZnO-based phosphors, such as field emissive display technology, etc.
Korean Journal of Chemical Engineering, 2006
Synthesis of ZnO nanowires was achieved on Si(100) substrate by the thermal evaporation of high purity metallic zinc powder without the use of any metal catalyst or additives. The diameter and length of the as-grown nanowires were in the range of 20–35 nm and few micrometers, respectively. The shapes and sizes of ZnO nanowires were dependent on the growth time. The high resolution transmission electron microscopy and selected area electron diffraction patterns indicated that the as-grown products are single crystalline with wurtzite hexagonal phase. Room temperature photoluminescence studies exhibited a strong UV emission and a suppressed green emission, confirming the good optical properties for the deposited nanowires.