Electrical and Magnetic Properties of Doped ZnO Nanowires (original) (raw)
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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.
Electric-field control of ferromagnetism in Mn-doped ZnO nanowires
Nano letters, 2014
In this Letter, the electric-field control of ferromagnetism was demonstrated in a back-gated Mn-doped ZnO (Mn-ZnO) nanowire (NW) field-effect transistor (FET). The ZnO NWs were synthesized by a thermal evaporation method, and the Mn doping of 1 atom % was subsequently carried out in a MBE system using a gas-phase surface diffusion process. Detailed structural analysis confirmed the single crystallinity of Mn-ZnO NWs and excluded the presence of any precipitates or secondary phases. For the transistor, the field-effect mobility and n-type carrier concentration were estimated to be 0.65 cm(2)/V·s and 6.82 × 10(18) cm(-3), respectively. The magnetic hysteresis curves measured under different temperatures (T = 10-350 K) clearly demonstrate the presence of ferromagnetism above room temperature. It suggests that the effect of quantum confinements in NWs improves Tc, and meanwhile minimizes crystalline defects. The magnetoresistace (MR) of a single Mn-ZnO NW was observed up to 50 K. Most ...
Spatially-Resolved Study of Magnetic Properties of Mn-Doped ZnO Quantum Wires
Journal of the Korean Physical Society, 2007
ZnO nanowires prepared by thermal growth following direct chemical synthesis and doped by Mn and by Mn and Sn impurities were investigated. The nanowires show a single crystal structure and a strong blue shift of the near band edge luminescence, which is attributed to the quantum confinement effect. The magnetic susceptibility of the quantum wires as a function of temperature demonstrated a Curie-Weiss behavior. Hysteresis with a coercive field <200 Oe was clearly observed in the magnetization versus field curves at 300 K. Increasing the Mn concentration by Mn and Sn co-doping significantly increased the magnetic hysteresis and the ferromagnetic behavior of the nanowires. Magnetic force microscopy measurements with high spatial resolution revealed a magnetic domain structure in the individual wires. The magnetic domains align perpendicular to the surface and can be controlled by using an external magnetic field.
Co-DOPED ZnO NANOWIRES GROWN BY VAPOR-LIQUID-SOLID METHOD: STRUCTURAL, OPTICAL AND MAGNETIC STUDIES
2012
We report on the growth of Co-doped ZnO nanowires (NWs) on Si substrate using a self-catalytic vapor deposition method from a Co-doped ZnO nanopowder source and study its structural, optical and magnetic properties for the as-grown and rapid thermal annealed samples. Co (5%)-doped ZnO (ZnCoO) nanoparticles (NPs) are used as source material for the growth process. Electron microscopy imaging clearly reveals the formation of long ZnO NWs with uniform diameter. X-ray di®raction analysis con¯rms the single crystalline hexagonal structure of Co-doped ZnO NWs without impurities of metallic cobalt or other phases. Micro-Raman studies of doped samples show doping/disorder induced additional modes as compared to the undoped ZnO. Room temperature photoluminescence spectra of the doped ZnO NWs show strong emission band at 380nmandnosigni¯cantemissionwasobservedinthevisibleregionindicatinglowdefectcontentintheNWs.Theˉelddependentmagnetization(MAˋHcurve)measuredatroomtemperatureexhibitsparamagneticnaturefortheNWswiththemagneticmomentintherange2Aˋ3.7milli−emu/cm2fortheappliedeldof2Tesla,whilethesourceZnCoONPsexhibitroomtemperatureferromagnetismwithsaturationmagnetization380 nm and no signi¯cant emission was observed in the visible region indicating low defect content in the NWs. Thē eld dependent magnetization (MÀH curve) measured at room temperature exhibits paramagnetic nature for the NWs with the magnetic moment in the range 2À3.7 milli-emu/cm 2 for the applied eld of 2 Tesla, while the source ZnCoO NPs exhibit room temperature ferromagnetism with saturation magnetization 380nmandnosigni¯cantemissionwasobservedinthevisibleregionindicatinglowdefectcontentintheNWs.Theˉelddependentmagnetization(MAˋHcurve)measuredatroomtemperatureexhibitsparamagneticnaturefortheNWswiththemagneticmomentintherange2Aˋ3.7milli−emu/cm2fortheappliedeldof2Tesla,whilethesourceZnCoONPsexhibitroomtemperatureferromagnetismwithsaturationmagnetization6 emu/g. Possible mechanism of alteration in magnetic behavior in doped NWs are discussed based on the growth conditions and role of defects.
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, 2010
The e!ect of transformations induced by annealing on the structure and magnetic properties of -Fe O antiferromagnetic nanoparticles synthesized by chemical route has been investigated by transmission electron microscopy, magnetization measurements and MoK ssbauer spectroscopy. Annealing of these samples re-crystallize the nanoparticles without changing its mean size modifying the crystalline anisotropy energy of the nanoparticles leading to a change in the reversible}irreversible regime and in the Morin transition behaviour.
Growth and characterization of Mn and Co-doped ZnO nanowires
Mikrochimica Acta, 2006
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.