The Effect of Mn Concentration on Curie Temperature and Magnetic Behavior of MOCVD Grown GaMnN Films

2004 ◽  
Vol 834 ◽  
Author(s):  
Erkan Acar Berkman ◽  
Mason J. Reed ◽  
F. Erdem Arkun ◽  
Nadia A. El-Masry ◽  
John M. Zavada ◽  
...  
Keyword(s):  
Curie Temperature ◽  
Fermi Level ◽  
Solid Solutions ◽  
Room Temperature ◽  
Growth Conditions ◽  
Ferromagnetic Behavior ◽  
Secondary Phases ◽  
Mn Doping ◽  
Mn Concentration

ABSTRACTWe report on the growth and characterization of dilute magnetic semiconductor GaMnN showing ferromagnetism behavior above room temperature. GaMnN films were grown by MOCVD using (EtCp2)Mn as the precursor for in-situ Mn doping. Structural characterization of the GaMnN films was achieved by XRD, SIMS and TEM measurements. XRD and TEM confirmed that the films were single crystal solid solutions without the presence of secondary phases. SIMS analysis verified that Mn was incorporated homogeneously throughout the GaMnN layer which was ∼0.7μm thick. Ferromagnetic behavior for these films was observed along the c-direction (out of plane orientation) in a Mn concentration range of 0.025–2%. The saturation magnetization ranged from 0.18–1.05 emu/cc for different growth conditions. Curie temperatures of the GaMnN films were determined to be from 270 to above 400K depending on the Mn concentration. This dependence of Curie temperature on concentration of Mn in GaMnN indicates that the grown films are random solid solutions. SQUID measurements ruled out the possibility of spin-glass and superparamagnetism in these MOCVD grown GaMnN films. The grown films were electrically semi-insulating; however PL measurements showed that the films were still optically active after Mn doping. This study showed that the growth of III-Nitride films doped with Mn requires a small window of growth conditions that depend on growth temperature and (EtCp)2Mn flux to achieve ferromagnetism above room temperature, and the magnetic response of the film depends on the Fermi level position. We suggest that ferromagnetism occurs when the Fermi level lies within the Mn energy level which is 1.4 eV above the GaN valence band.

Photoluminescence and Magnetic Properties of Undoped and (Mn, Co) co-doped ZnO Nanoparticles

2020 ◽  
Vol 16 (4) ◽  
pp. 655-666
Author(s):  
Mona Rekaby
Keyword(s):  
Magnetic Properties ◽  
Zno Nanoparticles ◽  
Room Temperature ◽  
Magnetic Measurements ◽  
Structural Defects ◽  
Ferromagnetic Behavior ◽  
Secondary Phases ◽  
Antiferromagnetic Ordering ◽  
Doped Zno ◽  
Co Doped

Objective: The influence of Manganese (Mn2+) and Cobalt (Co2+) ions doping on the optical and magnetic properties of ZnO nanoparticles was studied. Methods: Nanoparticle samples of type ZnO, Zn0.97Mn0.03O, Zn0.96Mn0.03Co0.01O, Zn0.95Mn0.03 Co0.02O, Zn0.93Mn0.03Co0.04O, and Zn0.91Mn0.03Co0.06O were synthesized using the wet chemical coprecipitation method. Results: X-ray powder diffraction (XRD) patterns revealed that the prepared samples exhibited a single phase of hexagonal wurtzite structure without any existence of secondary phases. Transmission electron microscope (TEM) images clarified that Co doping at high concentrations has the ability to alter the morphologies of the samples from spherical shaped nanoparticles (NPS) to nanorods (NRs) shaped particles. The different vibrational modes of the prepared samples were analyzed through Fourier transform infrared (FTIR) measurements. The optical characteristics and structural defects of the samples were studied through Photoluminescence (PL) spectroscopy. PL results clarified that Mn2+ and Co2+ doping quenched the recombination of electron-hole pairs and enhanced the number of point defects relative to the undoped ZnO sample. Magnetic measurements were carried out at room temperature using a vibrating sample magnetometer (VSM). (Mn, Co) co-doped ZnO samples exhibited a ferromagnetic behavior coupled with paramagnetic and weak diamagnetic contributions. Conclusion: Mn2+ and Co2+ doping enhanced the room temperature Ferromagnetic (RTFM) behavior of ZnO. In addition, the signature for antiferromagnetic ordering between the Co ions was revealed. Moreover, a strong correlation between the magnetic and optical behavior of the (Mn, Co) co-doped ZnO was analyzed.

Characterization of heterogeneities in detector-grade CdZnTe crystals

2009 ◽  
Vol 24 (4) ◽  
pp. 1361-1367 ◽  
Author(s):  
M.C. Duff ◽  
D.B. Hunter ◽  
A. Burger ◽  
M. Groza ◽  
V. Buliga ◽  
...  
Keyword(s):  
Room Temperature ◽  
Collection Efficiency ◽  
Analytical Techniques ◽  
Charge Collection ◽  
Secondary Phases ◽  
Charge Collection Efficiency

Synthetic Cd1–xZnxTe or “CZT” crystals are highly suitable for γ-spectrometers operating at room temperature. Secondary phases (SP) within CZT, presumed to be Te metal, have detrimental impacts on the charge collection efficiency of fabricated device. Using analytical techniques rather than arbitrary theoretical definitions, we identify two SP morphologies: (i) many void, 20-μm “negative” crystals with 65-nm nanoparticle residues of Si, Cd, Zn, and Te and (ii) 20-μm hexagonal-shaped bodies, which are composites of metallic Te layers with cores of amorphous and polycrystalline CZT material that surround the voids.

Synthesis and Characterization of BaTiO3-(Bi0.5Na0.5)TiO3 Solid Solution Based Dielectric Ceramics

2012 ◽  
Vol 512-515 ◽  
pp. 1160-1164
Author(s):  
Guo Feng Yao ◽  
Xiao Hui Wang ◽  
Long Tu Li
Keyword(s):  
Solid Solution ◽  
Dielectric Properties ◽  
Solid State ◽  
Curie Temperature ◽  
Solid Solutions ◽  
Solid State Reaction ◽  
Synthesis And Characterization ◽  
Conventional Solid State Reaction ◽  
Dielectric Ceramics

BaTiO3-(Bi0.5Na0.5)TiO3 (BTBNT) solid solution ceramics with the Curie temperature higher than 150°C were prepared, which were promising for X9R MLCCs application. (Bi0.5Na0.5)TiO3 (BNT) was first synthesized by the conventional solid state reaction and then it was mixed with BaTiO3 (BT) with increasing BNT content from 0 to 12 mol%. BaTiO3-(Bi0.5Na0.5TiO3 solid solutions were obtained after calcining at 1100°C. The structural and dielectric properties of BTBNT and Nb-doped BTBNT ceramics were investigated.

scholarly journals Characterization of Pd Impurities and Finite-Sized Defects in Detector Grade CdZnTe

2011 ◽  
Vol 1341 ◽  
Author(s):  
M.C. Duff ◽  
J.P. Bradley ◽  
Z.R. Dai ◽  
N. Teslich ◽  
A. Burger ◽  
...  
Keyword(s):  
Room Temperature ◽  
Cubic Phase ◽  
Secondary Phases ◽  
Detector Performance ◽  
X Ray ◽  
Metal Impurities ◽  
Transmission Electron ◽  
Large Numbers ◽  
Topographic Imaging

ABSTRACTSynthetic CdZnTe or “CZT” crystals are highly suitable for γ-spectrometers operating at the room temperature. Secondary phases (SP) in CZT are known to inhibit detector performance, particularly when they are present in large numbers or dimensions. These SP may exist as voids or composites of non-cubic phase metallic Te layers with bodies of polycrystalline and amorphous CZT material and voids. Defects associated with crystal twining may also influence detector performance in CZT. Using transmission electron microscopy, we identify two types of defects that are on the nano scale. The first defect consists of 40 nm diameter metallic Pd/Te bodies on the grain boundaries of Te-rich composites. Although the nano-Pd/Te bodies around these composites may be unique to the growth source of this CZT material, noble metal impurities like these may contribute to SP formation in CZT. The second defect type consists of atom-scale grain boundary dislocations. Specifically, these involve inclined “finite-sized” planar defects or interfaces between layers of atoms that are associated with twins. Finite-sized twins may be responsible for the subtle but observable striations that can be seen with optical birefringence imaging and synchrotron X-ray topographic imaging.

Fabrication and characterization of magnetic porous silicon with curie temperature above room temperature

2017 ◽  
Vol 24 (5) ◽  
pp. 1139-1144 ◽  
Author(s):  
Mansour Aouassa ◽  
Imen Jadli ◽  
Mohammad Ali Zrir ◽  
Hassen Maaref ◽  
Ridha Mghaieth ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Curie Temperature ◽  
Room Temperature ◽  
Fabrication And Characterization

Hydrothermal Synthesis and Room Temperature Ferromagnetism of Ni-Doped Rod-Like ZnO Particles

2014 ◽  
Vol 934 ◽  
pp. 71-74
Author(s):  
Lian Mao Hang ◽  
Zhao Ji Zhang ◽  
Zhi Yong Zhang
Keyword(s):  
Quantum Interference ◽  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Hexagonal Wurtzite Structure ◽  
Ferromagnetic Behavior ◽  
Secondary Phases ◽  
Superconducting Quantum Interference Device ◽  
X Ray Diffraction ◽  
X Ray ◽  
Zno Particles

Ni-doped rod-like ZnO particles with doping concentration of 1 at.% were synthesized at 200°C by hydrothermal method and characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and superconducting quantum interference device (SQUID). The results show that the as-synthesized samples are pure hexagonal wurtzite structure without metallic Ni or other secondary phases and display rod-like shape with smooth surface. The magnetization measurements reveal that the Ni-doped rod-like ZnO particles show ferromagnetic behavior at room temperature. The saturation magnetization and coercive field are 0.0046 emu/g and 15 Oe, respectively.

Comparison of the Incorporation of Various Transition Metals into GaN by MOCVD

2006 ◽  
Vol 955 ◽  
Author(s):  
Matthew H Kane ◽  
William Fenwick ◽  
Nola Li ◽  
Shalini Gupta ◽  
Eun Hyun Park ◽  
...  
Keyword(s):  
Transition Metals ◽  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Magnetic Hysteresis ◽  
Chemical Vapor ◽  
Magnetic Ordering ◽  
Growth Conditions ◽  
Shallow Donor ◽  
Organic Chemical ◽  
Secondary Phases

ABSTRACTThe incorporation of transition metals in GaN has long been of interest in spintronics due to theoretical predictions of room temperature ferromagnetism in these materials. However, the mechanism of the observed ferromagnetism of the nitride-based DMS is still controversial, and may originate from a carrier-mediated, defect-related or nanoscale clustering mechanism. In this work, we present a comparative study of the incorporation of various transition metals and their effect on the optical, structural, and magnetic properties of GaN. Metal-organic chemical vapor deposition (MOCVD) has been employed to produce epitaxial films of varying thickness and manganese and iron doping using bis-cyclopentyldienyl(magnanese,iron) as the transition metal sources. High-resolution X-ray diffraction reveals no secondary phases under optimized growth conditions. Magnetic hysteresis is observed at room temperature in both GaMnN and GaFeN, though the strength of the magnetic ordering is roughly an order of magnitude weaker in the Fe-alloyed samples. Increasing Mn concentrations significantly affect long-range lattice ordering, and the observation of local vibrational modes (LVMs) supports the formation of nitrogen vacancies, even under optimized MOCVD growth conditions. Such vacancies form shallow donor complexes and thus contribute to self-compensation. A disorder-induced mode at 300 cm−1 and a LVM due to vacancies at 669 cm-1 were revealed by Raman spectroscopy.

Spectrofluorimetric Characterization of an Ionic Conductor: Sodium Sulfate High-Temperature Phases Doped with Europium(III)

1994 ◽  
Vol 369 ◽  
Author(s):  
Lowell R. Matithews ◽  
Edward T. Knobbe ◽  
Gamini Dharmasena ◽  
Renée Cole ◽  
Roger Frech
Keyword(s):  
Solid Solutions ◽  
Sodium Sulfate ◽  
National Science Foundation ◽  
Room Temperature ◽  
Local Environment ◽  
X Ray ◽  
National Science ◽  
Trivalent Cations ◽  
The Individual

AbstractThe highest-temperature polymorph of sodium sulfate, (I), has significant orientational disorder in its structure which allows it to readily accept substitution by di- and trivalent cations. Although Na2SO4 (I) exhibits reasonable ionic conductivity, it cannot be quenched to room temperature without changing phase. However, aliovalent solid solutions of (I) can be quenched to RT and resultant cation vacancies promote conduction via Na+ migration. The closely related but more ordered phase Na2SO4 (III) can also form aliovalent solid solutions which can be quenched to RT.The europium(III) ion is an extremely sensitive and useful probe of its immediate local environment. The presence, location, and intensity of its fluorescence transitions (particularly the 5D0→7F0-2 emissions) can provide detailed information about the symmetry, nature, and multiplicity of the individual Eu3+ site which cannot be gained from X-ray or neutron diffraction techniques.Our research (supported by the National Science Foundation and the State of Oklahoma) involves the structural characterization of two europium-doped sodium sulfate phases via fluorescence spectroscopy.

Contactless Electromodulation Characterization of Compound Semiconductor Surfaces and Device Structures

1993 ◽  
Vol 324 ◽  
Author(s):  
J.M. Woodall
Keyword(s):  
Fermi Level ◽  
Electric Fields ◽  
Growth Conditions ◽  
Compound Semiconductor ◽  
Conduction Band Edge ◽  
Semiconductor Surfaces ◽  
Air Exposure ◽  
Fermi Level Pinning ◽  
Characterization Of Properties

AbstractThis paper will review the use of contactless electromodulation methods, such as photoreflectance (PR) and contactless electroreflectance (CER), to characterize the electronic properties of compound semiconductor surfaces exposed to different growth and post-growth conditions. Also the characterization of properties critical to device performance can be evaluated. For example, using PR and CER it has been found that there is a lower density of surface hole traps than electron traps in certain as-grown MBE (001) GaAs samples and that this condition persists even after air exposure. This behaviour is in contrast to other samples, including both bulk and MBE grown (001) surfaces in which the Fermi level is pinned mid-gap for both n- and p-type structures. We also have observed that Ar+ bombardment under UHV conditions results in Fermi level pinning close to the conduction band edge and that thermal annealing restores mid-gap pinning. Finally, using PR we are able to characterize the electric fields and associated doping levels in the emitter and collector regions of heterojunction bipolar transistor structures (fabricated from III-V materials), thus demonstrating the ability to perform inprocess evaluation of important device parameters.

Preparation and Characterization of Well-Dispersed Nd1.6Eu0.4Zr2O7 Solid Solution and its Fluorescent Behavior

2010 ◽  
Vol 97-101 ◽  
pp. 182-186
Author(s):  
Yu Ping Tong ◽  
Jing Wang ◽  
Rui Zhu Zhang ◽  
Shun Bo Zhao
Keyword(s):  
Solid Solution ◽  
Solid Solutions ◽  
Room Temperature ◽  
Single Phase ◽  
Combustion Process ◽  
Crystal Form ◽  
Scherrer Formula ◽  
Xrd Patterns ◽  
Average Size

Well-dispersed Nd1.6Eu0.4Zr2O7 solid solutions were successfully prepared by a convenient salt-assisted combustion process using glycine as fuel. The samples were characterized by XRD, Raman, TEM and HRTEM. The results showed that the Nd ion can be partially replaced by Eu ion. The substituted product was still single-phase solid solutions and the crystal form remained unchanged. TEM images showed that the Nd1.6Eu0.4Zr2O7 solid solutions were composed of well-dispersed sphere-shaped nanocrystals with an average size of 30 nm, which is consistent with the value obtained from XRD patterns using the Scherrer formula. Moreover, the fluorescent characterization of the Nd1.6Eu0.4Zr2O7 nanocrystals at 385 nm upon excitation was carried out at room temperature, and the results showed that there were some intense and prevailing emission peaks located at 590-650 nm.

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