Download or read book Synthesis and characterization of 3d transation metal ions doped ZnO based dilute magnetic semiconductor thin films written by Kousik Samanta and published by . This book was released on 2009 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Structure and Properties of 3d Transition Metal Doped ZnO written by Venkaiah Malapati and published by LAP Lambert Academic Publishing. This book was released on 2014-08-27 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: ZnO based semiconductors as transparent electrodes have given wide range of applications in optoelectronic devices due to their wide band gap replacing the conventional GaN semiconductors. This book is the compilation of the work of Venkaiah Malapati which deals with the synthesis and characterization of an interesting room temperature undoped and 3d transition metal doped ZnO thin films by rf magnetron sputtering. this work addresses the following three major questions... (1) what is the effect of working gas pressure on the properties of undoped and Mn, Fe and Mn-Fe co-doped ZnO thin films. Here, the effect of argon and oxygen gas pressure studied undoped and Mn and Fe doped thin films studied. This book includes a systematic study of structure, morphology, optical, mechanical and magnetic properties of undoped Mn, Fe doped ZnO thin films studied. This book should be useful to readers in enhancing their knowledge about thin film preparation and their characterization.

Download or read book DEFECTS AND FERROMAGNETISM IN TRANSITION METAL DOPED ZINC OXIDE written by Sunil Thapa and published by . This book was released on 2016 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transition metal doped zinc oxide has been studied recently due to its potential application in spintronic devices. The magnetic semiconductor, often called Diluted Magnetic Semiconductors (DMS), has the ability to incorporate both charge and spin into a single formalism. Despite a large number of studies on ferromagnetism in ZnO based DMS and the realization of its room temperature ferromagnetism, there is still a debate about the origin of the ferromagnetism. In this work, the synthesis and characterization of transition metal doped zinc oxide have been carried out. The sol-gel method was used to synthesize thin films, and they were subsequently annealed in air. Characterization of doped zinc oxide films was carried out using the UV-visible range spectrometer, scanning electron microscopy, superconducting quantum interference device (SQUID), x-ray diffraction(XRD) and positron annihilation spectroscopy. Hysteresis loops were obtained for copper and manganese doped zinc oxide, but a reversed hysteresis loop was observed for 2% Al 3% Co doped zinc oxide. The reversed hysteresis loop has been explained using a two-layer model.

Download or read book Transition Metal Ions Doped Zno Nanopowders written by B. Babu and published by LAP Lambert Academic Publishing. This book was released on 2015-02-16 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: Intensive research on semiconductor nanomaterials has increased remarkably during the past years due to their unique characteristics. Wide-band gap oxide semiconductors have occupied the forefront because of an increasing need for short wavelength photonic devices, high-power, high-frequency electronic devices. Doping with proper metal elements via introducing acceptor or donor in host material is an effective approach to tune the materials with requisite properties. Among different magnetic semiconductor materials, 3d transition metal doped ZnO has received maximum attention due to the observation of room temperature ferromagnetism with suitable magnetic dopant ions. Therefore, selection of proper doping element in ZnO has become an important route for enhancing and controlling electrical, optical and magnetic performances of nanomaterials. The objective of the present investigation is to synthesis, structural, spectroscopic and magnetic properties of transition metal ions doped ZnO nanopowders by solid state reaction with sonochemical assistance. The synthesized powders are characterized by XRD, SEM, Optical absorption, PL, FT-IR, EPR and VSM techniques.

Download or read book Transition Metal Doped Spintronics Materials written by R. Saravanan and published by Materials Research Forum LLC. This book was released on 2023-02-15 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book presents new research on the synthesis and characterization of various oxide based dilute magnetic spintronics materials (ODMS). The characterization techniques included powder X-ray diffraction, scanning electron microscopy, vibrating sample magnetometry and UV visible spectrometry. The morphological, magnetic and optical properties are reported. Electron density distribution studies are presented in the form of three, two and one dimensional electron density maps. Keywords: Spintronics Materials, Zn1-xTixO, Zn1-xFexO, Zn1-xVxO, Zn1-xNix/2Vx/2O, Synthesis, X-ray Diffraction. Rietveld Analysis, Surface Morphological Properties, Optical Properties, Magnetic Properties, Charge Density Analysis, Electron Density Distribution.

Download or read book ZnO and Their Hybrid Nano Structures written by Gaurav Sharma and published by Materials Research Forum LLC. This book was released on 2023-06-05 with total page 333 pages. Available in PDF, EPUB and Kindle. Book excerpt: ZnO and its hybrid nanostructures have unique optical, physical and chemical properties. The book covers recent trends in processing techniques and applications. Topics include solar cells, photo-voltaic devices, fuel cells, uv filters, lasers, light-emitting diodes, photo-detectors, spin-tronic devices, magnetic semiconductors, nano-generators, piezotronics, photo-catalytic applications against harmful organic pollutants like dyes, heavy metals, antibiotics, and sensors such as bio sensors, chemical sensors, gas sensors. Keywords: ZnO, Nano ZnO, Point Defects, Magnetic Semiconductors, Hybrid Nanostructures, Cell Applications, Nanoadsorbant for Heavy Metal Removals, Diagnostics, ZnO Nano-Carriers, ZnO Thin Films Fabrication.

Download or read book Physical Properties of Dilute Magnetic Semiconducting Oxides written by Sudipta Bandyopadhyay and published by LAP Lambert Academic Publishing. This book was released on 2014-11-19 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transition metal doped ZnO has been studied from the perspective of its suitability in electronic applications. Bulk samples of Mn doped ZnO has been synthesized by solid state reaction and sol-gel techniques. Thin films of Mn doped ZnO has been synthesized by only sol-gel spin coating technique. So far as Co doped ZnO is concerned it is basically Co co-doped AZO [Al doped ZnO] film synthesized by sol-gel dip coating technique. Above 3 at% of Mn doping impurity phase has been developed for bulk powder sample. The impurity phase was completely or partially dissolved by ion beam irradiation. The role of Zn vacancy and substitutional replacement of Mn at Zn site is crucial for intrinsic ferromagnetism. Further counterbalancing antiferromagnetism and paramagnetism are also present. 2 at% Mn doped ZnO powder sample indicate metal insulator transition. Mn doped ZnO films exhibit defect induced ferromagnetism and interpreted in terms of bound magnetic polaron. Zn Vacancy favours and oxygen vacancy opposes intrinsic ferromagnetism in Mn doped ZnO film. Highly conducting Co co-doped AZO films shows potential for applications with interesting low temperature resistivity behaviour.

Download or read book Synthesis of Doped ZnO Based Bulk Dilute Magnetic Semiconductors and Their Nanophase Thin Films Using Pulsed Laser Ablation written by Shumaila Karamat and published by . This book was released on 2011 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Study of Titanium Dioxide Based Dilute Magnetic Semiconductors written by Bakhtyar Ali and published by ProQuest. This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Dilute magnetic semiconductors (DMSs) with high Curie temperature are highly desirable in spintronics applications. Transition metal doped oxides such as cobalt (Co), chromium (Cr), copper (Cu) doped TiO 2, ZnO, and SnO 2 are being studied for the last few years. Among other DMSs Co x Ti (1-x) O 2 anatase and rutile has been observed to have high T c (~400K). It is transparent in the visible and near infrared regions with a sizable band gap and appreciable conductivity. Therefore, it is believed to be very useful candidate for the fabrication of magnetic semiconductor devices. It has been shown that the achievement of magnetic percolation effect in DMSs is strongly linked to the nature of dopant and synthesis procedure which eventually leads to defects in the material. In this thesis we report the study of Co doped TiO 2 thin films and Cu:Co codoped TiO 2 nanopowders. Thin films of Co doped TiO 2 on silicon and quartz substrates are synthesized by pulsed laser deposition (PLD). Various oxygen partial pressures (P O2), ranging from 6.6 mPa to 53 Pa, are used to vary the oxygen content in the samples. Crystal structure and transport/ magnetic properties of Co x Ti 1-x O 2 (0.01 = x= 0.06) thin films are found to have a strong dependence on oxygen stoichiometry. X-ray diffraction (XRD) data reveal the presence of mixed phase material containing both anatase and rutile. However, the stability of each phase depends on the P O2 present in the chamber during the growth of the films. X-ray Photoelectron Spectroscopy (XPS) shows that Co is substituted in TiO 2 and is in the 2+ oxidation state. There is an enhancement in electrical conductivity and magnetization resulting from off stoichiometric (deficient) oxygen. The resistivity data fit well with the simple thermal activation model, giving activation energy values of 20 to 140 meV. In the second part we have studied the role of Cu codoping and oxygen vacancies in enhancing/stabilizing room temperature ferromagnetic interactions in Co doped TiO 2 nanopowder (cobalt being 5%, well bellow the cation percolation limit for TiO 2). Analyses of the XRD, TEM and XPS data reveal the cobalt incorporation into the lattice structure with no sign of phase segregations. The as-prepared paramagnetic Co-TiO 2 powder is rendered ferromagnetic by controlling the point defects (oxygen vacancies) in the sample. Interestingly, Cu codoping enhances the magnetization by an order of magnitude in the reduced Co doped TiO 2 . We believe that impurity band exchange mechanism is a plausible model in our Co-TiO 2 sample. The implication of the effect of Cu doping in Co doped sample is also discussed. We have also shown that the enhancement of ferromagnetism with additional doping in Co doped TiO 2 is a reversible effect.

Download or read book Doped Transition Metal Oxide and Ferrite Nanocrystals written by Sasanka Deka and published by LAP Lambert Academic Publishing. This book was released on 2011-04 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanosized magnetic materials have received great attention and importance during the last decade. Nanomagnetic material is one of the hottest subjects of present day research activities. The physical properties of nanosized magnetic materials differ considerably from that of their bulk counterparts and the magnetic characteristics of many materials can be tuned by reducing their size. The objectives of this research work are the synthesis and studies on the structural and magnetic properties of some selected transition metal oxides and ferrites in nanocrystalline form. The research work has been carried out on transition metal ion doped zinc oxide (ZnO) based diluted magnetic semiconductors (DMSs), some ferrites (for instance, Zn-ferrite, NiZn-ferrite, maghemite, etc.) and magnetopolymer nanocomposite systems. The respective nanocrystalline oxides are synthesized using a simple solution combustion method and characterized using various techniques. The results from the studies on different materials are presented in this thesis, consisting of six chapters. Last but not the least, several performance parameters have been measured and conditions for best results have been discussed.

Download or read book Novel Diluted Magnetic Semiconductor Materials based on Zinc Oxide written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary aim of this work was to develop a ZnO based diluted magnetic semiconductor (DMS) materials system which displays ferromagnetism above room temperature and to understand the origin of long-range ferromagnetic ordering in these systems. Recent developments in the field of spintronics (spin based electronics) have led to an extensive search for materials in which semiconducting properties can be integrated with magnetic properties to realize the objective of successful fabrication of spin-based devices. For these devices we require a high efficiency of spin current injection at room temperature. Diluted magnetic semiconductors (DMS) can serve this role, but they should not only display room temperature ferromagnetism (RTFM) but also be capable of generating spin polarized carriers. Transition metal doped ZnO has proved to be a potential candidate as a DMS showing RTFM. The origin of ferromagnetic ordering in ZnO is still under debate. However, the presence of magnetic secondary phases, composition fluctuations and nanoclusters could also explain the observation of ferromagnetism in the DMS samples. This encouraged us to investigate Cu-doped(+ ư spin in the 2+ valence state) ZnO system as a probable candidate exhibiting RTFM because neither metallic Cu nor its oxides (Cu2O or CuO) are ferromagnetic. The role of defects and free carriers on the ferromagnetic ordering of Cu-doped ZnO thin films was studied to ascertain the origin of ferromagnetism in this system. A novel non-equilibrium Pulsed Laser Deposition technique has been used to grow high quality epitaxial thin films of Cu:ZnO and (Co, Cu):ZnO on c-plane Sapphire by domain matching epitxay. Both the systems showed ferromagnetic ordering above 300K but Cu ions showed a much stronger ferromagnetic ordering than Co, especially at low concentrations (1-2 %) of Cu where we realized near 100% polarization. But, the incorporation of Cu resulted in a 2-order of magnitude rise in the resistivity from 10-1 t.

Download or read book Diluted Magnetic Semiconductor ZnO written by Kuldeep Chand Verma and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: For advancement in future spintronics, the diluted magnetic semiconductors (DMSs) might be understood for their origin of ferromagnetic aptness. It not much clear to the ferromagnetism in DMS, that is intrinsic or via dopant clustering formation. For this, we have included a review study for the doping of transition metal and rare earth ions in ZnO. It is realized that the antiferromagnetic ordering is found in doped ZnO to achieve high-TC ferromagnetism. X-ray diffraction and Raman spectra techniques have been used to detect the wurtzite ZnO structure and lattice defects. Since ZnO has different types of morphology formation that is generally dependent on synthesis conditions and dopant level. The band gap energy of ZnO and lattice defect formation are shown by photoluminescence technique. The room temperature ferromagnetism is described with bound magnetic polaron (BMP) model in which oxygen vacancies play a major role. However, the temperature-dependent conditions are responsible for ferromagnetic ordering. The first principle calculation is used for dopant ions in ZnO for their replacement of Zn2+ atoms in the wurtzite structure as well as magnetic contribution.

Download or read book Zinc Oxide Bulk Thin Films and Nanostructures written by Chennupati Jagadish and published by Elsevier. This book was released on 2011-10-10 with total page 600 pages. Available in PDF, EPUB and Kindle. Book excerpt: With an in-depth exploration of the following topics, this book covers the broad uses of zinc oxide within the fields of materials science and engineering:- Recent advances in bulk , thin film and nanowire growth of ZnO (including MBE, MOCVD and PLD), - The characterization of the resulting material (including the related ternary systems ZgMgO and ZnCdO), - Improvements in device processing modules (including ion implantation for doping and isolation ,Ohmic and Schottky contacts , wet and dry etching), - The role of impurities and defects on materials properties - Applications of ZnO in UV light emitters/detectors, gas, biological and chemical-sensing, transparent electronics, spintronics and thin film

Download or read book Hydrothermal Synthesis and Characterization of Cobalt Doped Dilute Magnetic Semiconducting Nanoparticles written by Sirish Chandra Bhamidipati and published by . This book was released on 2012 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is great deal of interest in transparent Dilute Magnetic Semiconductors (DMS) due to their potential applications in spintronics. Nanomaterials of transition-metal doped ZnO DMS are considered as ideal systems for carrying out research in the field of spintronics as they can successully combine magnetism and electronics in a single material. In this thesis, ZnO and Co-doped ZnO nanorods have been synthesized by hydrothermal method using aqueous solutions of Zn (NO3)2 .6H2), Co (C2H3OO)2.4H2O, and NH4OH as hydrolytic catalyst. Pure as well as transition element doped ZnO nanomaterials with different sizes and shapes have been synthesized through changing process parameters such as molarity of the precursors, pH of the final mixture, growth and annealing temperature and time during the hydrothermal process. Structural, magnetic, and optical properties are studied using available state-of-the-art techniques such as X-ray diffration (XRD), field emission scanning electron microscopy (FESEM), superconducting quantum interference device (SQUID) magnetometer and ultraviolet-visible spectroscopy. XRD and SEM studies have revealed nanorods with hexagonal Wurtzite structure with length in the range of 200 to 5000 nm, and cross section in the range of 30 to 500 nm. Magnetization data suggest an existence of complex magnetic structure in the (10%, 5%, 2%) Co-doped ZnO nanomaterials. Further investigation is required to better understand the complex nature of magnetic properties in transition metal doped DMS. Understanding of DMS is critical for the future spin-electronics.

Download or read book Doping in Zinc Oxide Thin Films written by Zheng Yang and published by . This book was released on 2009 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: Doping in zinc oxide (ZnO) thin films is discussed in this dissertation. The optimizations of undoped ZnO thin film growth using molecular-beam epitaxy (MBE) are discussed. The effect of the oxygen ECR plasma power on the growth rate, structural, electrical, and optical properties of the ZnO thin films were studied. It was found that larger ECR power leads to higher growth rate, better crystallinity, lower electron carrier concentration, larger resistivity, and smaller density of non-radiative luminescence centers in the ZnO thin films. Low-temperature photoluminescence (PL) measurements were carried out in undoped and Ga doped ZnO thin films grown by molecular-beam epitaxy. As the carrier concentration increases from 1.8 x 10 to 1.8 x 10 cm -3, the dominant PL line at 9 K changes from I 1 (3.368 - 3.371 eV), to I DA (3.317 - 3.321 eV), and finally to I 8 (3.359 eV). The dominance of I, due to ionized donor bound excitons, is unexpected in n-type samples, but is shown to be consistent with the temperature-dependent Hall fitting results. We also show that I DA has characteristics of a donor acceptor pair transition, and use a detailed, quantitative analysis to argue that it arises from Ga Zn donors paired with Zn-vacancy (V Zn) acceptors. In this analysis, the Ga Zn 0/+ energy is well-known from two-electron satellite transitions, and the V Zn 0/- energy is taken from a recent theoretical calculation. Typical behaviors of Sb-doped p -type ZnO are presented. The Sb doping mechanisms and preference in ZnO are discussed. Diluted magnetic semiconducting ZnO:Co thin films with above room-temperature T C were prepared. Transmission electron microscopy and x-ray diffraction studies indicate the ZnO:Co thin films are free of secondary phases. The magnetization of the ZnO:Co thin films shows a free electron carrier concentration dependence, which increases dramatically when the free electron carrier concentration exceeds ~10 19 cm -3, indicating a carrier-mediated mechanism for ferromagnetism. The anomalous Hall effect was observed in the ZnO:Co thin films. The anomalous Hall coefficient and its dependence on longitudinal resistivity were analyzed. The presence of a side-jump contribution further supports an intrinsic origin for ferromagnetism in ZnO:Co thin films. These observations together with the magnetic anisotropy and magnetoresistance results, supports an intrinsic carrier-mediated mechanism for ferromagnetic exchange in ZnO:Co diluted magnetic semiconductor materials. Well-above room temperature and electron-concentration dependent ferromagnetism was observed in n -type ZnO:Mn films, indicating long-range ferromagnetic order. Magnetic anisotropy was also observed in these ZnO:Mn films, which is another indication for intrinsic ferromagnetism. The electron-mediated ferromagnetism in n -type ZnO:Mn contradicts the existing theory that the magnetic exchange in ZnO:Mn materials is mediated by holes. Microstructural studies using transmission electron microscopy were performed on a ZnO:Mn diluted magnetic semiconductor thin film. The high-resolution imaging and electron diffraction reveal that the ZnO:Mn thin film has a high structual quality and is free of clustering/segregated phases. High-angle annular dark field imaging and x-ray diffraction patterns further support the absence of phase segregation in the film. Magnetotransport was studied on the ZnO:Mn samples, and from these measurements, the temperature dependence of the resistivity and magnetoresistance, electron carrier concentration, and anomalous Hall coefficient of the sample is discussed. The anomalous Hall coefficient depends on the resistivity, and from this relation, the presence of the quadratic dependence term supports the intrinsic spin-obit origin of the anomalous Hall effect in the ZnO:Mn thin film.

Download or read book Phase formation in multicomponent films based on 3d transition metals written by Smita Gangaprasad Rao and published by Linköping University Electronic Press. This book was released on 2021-03-18 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: The need for materials that enhance life span, performance, and sustainability has propelled research in alloy design from binary alloys to more complex systems such as multicomponent alloys. The CoCrFeMnNi alloy, more commonly known as the Cantor alloy, is one of the most studied systems in bulk as well as thin film. The addition of light elements such as boron, carbon, nitrogen, and oxygen is a means to alter the properties of these materials. The challenge lies in understanding the process of phase formation and microstructure evolution on addition of these light elements. To address this challenge, I investigate multicomponent alloys based on a simplified version of the Cantor alloy. My thesis investigates the addition of nitrogen into a Cantor variant system as a step towards understanding the full Cantor alloy. Me1-yNy (Me = Cr + Fe + Co, 0.14 ≤ y ≤0.28 thin films were grown by reactive magnetron sputtering. The films showed a change in structure from fcc to mixed fcc+bcc and finally a bcc-dominant film with increasing nitrogen content. The change in phase and microstructure influenced the mechanical and electrical properties of the films. A maximum hardness of 11 ± 0.7 GPa and lowest electrical resistivity of 28 ± 5 μΩcm were recorded in the film with mixed phase (fcc+bcc) crystal structure. Copper was added as a fourth metallic alloying element into the film with the mixed fcc + bcc structure, resulting in stabilization of the bcc phase even though Cu has been reported to be a fcc stabilizer. The energy brought to the substrate increases on Cu addition which promotes surface diffusion of the ions and leads to small but randomly oriented grains. The maximum hardness recorded by nanoindentation was found to be 13.7 ± 0.2 GPa for the sample Cu0.05. While it is generally believed that large amounts of Cu can be detrimental to thin film properties due to segregation, this study shows that small amounts of Cu in the multicomponent matrix could be beneficial in stabilizing phases as well as for mechanical properties. This thesis thus provides insights into the phase formation of nitrogen-containing multicomponent alloys.

Download or read book Effect of Strain Due to Substrates on Mn doped ZnO Dilute Magnetic Semiconductor Thin Films written by Srikanth Manchiraju and published by . This book was released on 2007 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: