Mn Impurities Research Articles

Cp2Mg-induced transition metal ion contamination and performance loss in MOCVD-grown blue emitting InGaN/GaN multiple quantum wells

The detrimental effects of Cp2Mg-induced trace transition metal (iron and manganese) contamination on the optical performance of metalorganic chemical vapor deposition (MOCVD)-grown blue-emitting InGaN/GaN multiple quantum wells (MQWs) are investigated experimentally. Five samples are grown at various stages of conditioning of a freshly installed MOCVD tool with stainless steel gas lines. Without conditioning, Cp2Mg flow induced Fe and Mn impurities with concentrations of 3×1015 and 3×1014 cm−3, respectively. These contaminants introduce nonradiative recombination centers with lifetimes on the order of nanoseconds. These impurities also induce indium-clustering related phenomena such as low energy shoulder at low temperature and a strong S-curve shift in emission energy with increasing temperature. Through successive cycles of chamber conditioning, the Fe and Mn concentrations decrease to below their detection limits, and the nonradiative recombination lifetime (+8 ns), internal quantum efficiency (+26%), microphotoluminescence nonuniformity (−4.7%), and S-curve shift (−26 meV) of the MQWs improved. The suppression of the transition metal ion contamination in the MOCVD chamber is shown to be crucial for high performance MQWs and blue light emitting diode growths.

Self-organization of various “phase-separated” nanostructures in a single chemical vapor deposition

Chemical vapor deposition (CVD) is one of the most versatile techniques for the controlled synthesis of functional nanomaterials. When multiple precursors are induced, the CVD process often gives rise to the growth of doped or alloy compounds. In this work, we demonstrate the self-assembly of a variety of ‘phase-separated’ functional nanostructures from a single CVD in the presence of various precursors. In specific, with silicon substrate and powder of Mn and SnTe as precursors, we achieved self-organized nanostructures including Si/SiOx core-shell nanowire heterostructures both with and without embedded manganese silicide particles, Mn11Si19 nanowires, and SnTe nanoplates. The Si/SiOx core-shell nanowires embedded with manganese silicide particles were grown along the direction of the crystalline Si via an Au-catalyzed vapor-liquid-solid process, in which the Si and Mn vapors were supplied from the heated silicon substrates and Mn powder, respectively. In contrast, direct vapor-solid deposition led to particle-free -oriented Si/SiOx core-shell nanowires and -oriented Mn11Si19 nanowires, a promising thermoelectric material. No Sn or Te impurities were detected in these nanostructures down to the experimental limit. Topological crystalline insulator SnTe nanoplates with dominant {100} and {111} facets were found to be free of Mn (and Si) impurities, although nanoparticles and nanowires containing Mn were found in the vicinity of the nanoplates. While multiple-channel transport was observed in the SnTe nanoplates, it may not be related to the topological surface states due to surface oxidation. Finally, we carried out thermodynamic analysis and density functional theory calculations to understand the ‘phase-separation’ phenomenon and further discuss general approaches to grow phase-pure samples when the precursors contain residual impurities.

Influence of 3d Transition Metal Impurities on Garnet Scintillator Afterglow

Garnet scintillators often suffer from undesired afterglow, the origin of which is not always well-understood. A possible origin is contamination with transition metal (TM) ions. These impurities can act as traps giving rise to afterglow. Alternatively, they may show long-lived (microsecond) d–d emission. Here we present a systematic study on the role of 3d TM impurities in (Lu,Gd)3(Ga,Al)5O12 garnet scintillators. Scintillator disks intentionally doped with ppm levels of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, or Zn were studied to identify TM-related traps in thermoluminescence (TSL) glow curves and their role in afterglow. For Ti, V, and Cr additional TSL peaks were observed that gave rise to RT afterglow in the 10–2–103 s time range, depending on garnet composition. On the millisecond time scale long-lived red/near-infrared emission was observed from Mn and Fe impurities, explained by spin-forbidden d–d emission. We show that afterglow can be reduced by the use of ultrapure raw materials. Other solutions include bandgap engineering for the garnet host to modify trap depths and applying optical filters to block the spin-forbidden d–d emission. The present study provides an insightful overview of the role of 3d TM impurities on afterglow in Ce-doped scintillators and procedures to predict and reduce afterglow. These insights will aid the development of Ce-doped garnets with superior afterglow behavior.

Exchange coupling and Mn valency in GaN doped with Mn and co-doped with Mg

We study 1 or 2 neighboring Mn impurities, as well as complexes of 1 Mn and 1 or 2 Mg ions in a 64 atoms supercell of GaN by means of density functional calculations. Taking into account the electron correlation in the local spin density approximation with explicit correction of the Hubbard term (the LSDA+U method) and full lattice relaxation we determine the nearest neighbor exchange J for a pair of Mn impurities. We find J to be ferromagnetic and of the order of about 18 meV in the Hamiltonian H=-2*J1*J2. That J is only weakly influenced by the U parameter (varying between 2 and 8 eV) and by the lattice relaxation. From a detailed analysis of the magnetization density distribution we get hints for a ferromagnetic super-exchange mechanism. Also the Mn valence was found to be 3+ without any doubt in the absence of co-doping with Mg. Co-doping with Mg leads to a valence change to 4+ for 1 Mg and to 5+ for 2 Mg. We show that the valence change can already be concluded from a careful analysis of the density of states of GaN doped with Mn without any Mg.

Preparation of High-Purity Lithium Carbonate Using Complexing Ion-Exchange Resins

Sorption of a series of alkaline earth and nonferrous metals (Ca, Mg, Cu, Ni, and Zn) from lithium hydrocarbonate and chloride solutions onto ion-exchange resins of various classes was studied. The highest values of the static exchange capacity were observed in sorption from a LiHCO3 solution onto imino carboxylic ion exchangers Amberlite IRC 748 (Rohm and Haas, the United States), Purolite S930 (Purolite, the United Kingdom), and AXIONIT 3S (AO Aksion RDM, Russia). In sorption from a LiCl solution with рН 1.4, the sorption capacity of all the sorbents tested is 3–7 lower. Sorption treatment of a LiHCO3 solution to remove Na, K, Са, Mg, Al, Si, Ti, Cr, Mn, Fe, Ni, Cu, and Zn impurities under dynamic conditions using AXIONIT 3S imino carboxylic sorbent was performed. The sorption ensures deep removal of Ca, Cu, and Zn impurities from a LiHCO3 solution. A procedure was suggested for preparing high-purity lithium carbonate by ion-exchange purification of a LiHCO3 solution on an imino carboxylic sorbent, followed by thermal decomposition of the purified solution at the boiling point to obtain a lithium carbonate precipitate. Lithium carbonate with the main substance content of 99.90 ± 0.05 wt % was obtained.

Manganese Clusterization in ZnS:Mn, Mg Synthesized by Self-Propagating High-Temperature Synthesis

The ZnS:Mn, Mg powder is fabricated by self-propagating high-temperature synthesis with the simultaneous introduction of Mn and Mg impurities. It is found that the simultaneous introduction of Mn and Mg impurities leads to the nonuniform distribution of manganese forming regions with a lower and higher Mn concentration. In the latter case, the manganese ions form paramagnetic clusters. At the same time, numerous centers of self-activated luminescence form in the synthesized ZnS:Mn, Mg due to mechanical stress and lattice strain. Additional annealing leads to a more uniform Mn distribution in the formed ZnS:Mn, Mg phosphor, which is accompanied by an increase in the intensity of the manganese photoluminescence band and quenching of the self-activated luminescence band.

Recovery of vanadium from leach solutions of vanadium slag using solvent extraction with N235

Leach solutions of vanadium (V) slag was generated from (NH4)2SO4 (AS) roasting and water leaching process. After separating titanium (Ti) from the solutions, the remaining liquor contains a large amount of V and iron (Fe). In this study, a system composed of trioctyl tertiary amine (N235) and sulfonated kerosene was used to separate V; moreover, the feasibility, mechanism, and energy evaluation of this system were also investigated. The results indicated that the single-stage V extraction rate was 86.35% using 40% N235 (v/v) and 60% sulfonated kerosene, an initial pH of 1.23, an organic/aqueous phase ratio (O/A) of 1.5:1, a temperature of 298.15 K, and an extraction time of 1 min. Based on McCabe-Thiele analysis, over 99% of the V was extracted by three-stage countercurrent extraction. Using the slope method and Fourier transform infrared (FT-IR) spectroscopy, the V extracted by N235 was proposed to exist as [(R3NH)4·H2V10O28]. Using 1.4 mol/L ammonia water, over 90% of the V could be stripped. The effects of the impurities Si, Ca, Al, Mg, and Mn on V recovery were negligible. A preliminary material and energy calculation (MEC) indicated that 113.64 kg V2O5 could be recovered from 1000 kg raw V slag using 5.57 × 106 kJ of heat and 974.45 kWh of electricity.

High-performance UV-B detectors based on MnxZn1-xS thin films modified by bandgap engineering

The high-speed performance ultraviolet (UV) detectors were successfully fabricated based on the ternary MnxZn1-xS (0.2 ≤ x ≤ 0.4) thin films deposited by a simple spray pyrolysis method. The optoelectrical properties of the samples were modified by introducing the Mn impurities at high content to enhance the performance of UV detectors. Microstructural characteristics confirmed the well-incorporation of Mn2+ ions into the ZnS lattice having nanocrystalline nature with homogeneous surface and strong adherence to the substrates. The optical measurements revealed that at the higher Mn2+ concentration, the optical transmittance increased over 95 % in the visible to near-infrared regions. Compared to the pure ZnS, the values of bandgap energy were found to blue-shift about 0.14 eV due to both quantum confinement and Burstein-Moss theories. Meanwhile, the Urbach energy decreased dramatically, leading to a considerable reduction of the electron-phonon interaction. The photoluminescence (PL) spectra revealed that the PL emission intensity was enhanced by introducing excess charge carriers through increasing the Mn2+ concentration, which can improve the generation of electron-hole pairs in the alloys. The photoresponse characterization featured a tremendous photosensing and photoswitching for the fabricated UV detectors, in which an excellent UV-B responsivity and high visible rejection were observed for the devices. For the UV detector based on the Mn0.4Zn0.6S thin film, the current gain greatly improved over 4.5 times compared to the pure ZnS one. Likewise, the photoresponse speed of the samples was found to enhance over 5 times, considerably.

Parameters of ZnO Semiconductor Films Doped with Mn and Fe 3d Impurities

The effect of Fe and Mn impurities on the magnetic parameters of ZnO wide-gap semiconductor films produced by high-frequency sputtering with wide variations in the defect concentration is studied. The introduction of Mn and Fe magnetic impurities brings about the existence of a magnetically ordered state in the semiconductor matrix, with different positions of the axis of easy magnetization. In the case of doping with Mn, this axis lies perpendicularly to the film plane, and in the case of doping with Fe, this axis lies in the film plane.

Analysis of Fe and Mn impurities in Chinese sponge titanium enterprise using an input-output model

The impurity content is an important index reflecting the quality of sponge titanium, especially Fe and Mn impurities. However, at present, only qualitative research has been conducted on the input of impurities, and no quantitative research has been conducted on the input and output of impurities. Therefore, based on the input-output model, this study analyzes the input and output of typical impurities in the magnesiothermic reduction-vacuum distillation process, product sorting process, and magnesium processing process, respectively. Quantitative characterization of the input and output of impurities in sponge titanium production. The results show that the Fe impurity is mainly input by the equipment, and the Mn impurity is mainly input from the raw materials. Determined the chemical reactions of impurities Fe and Mn during reduction, impurities of Fe and Mn exist in the product as the form of simple substance after the reaction.

Кластеризация марганца в ZnS : Mn, Mg, полученного методом высокотемпературного самораспространяющегося синтеза

Abstract The ZnS:Mn, Mg powder is fabricated by self-propagating high-temperature synthesis with the simultaneous introduction of Mn and Mg impurities. It is found that the simultaneous introduction of Mn and Mg impurities leads to the nonuniform distribution of manganese forming regions with a lower and higher Mn concentration. In the latter case, the manganese ions form paramagnetic clusters. At the same time, numerous centers of self-activated luminescence form in the synthesized ZnS:Mn, Mg due to mechanical stress and lattice strain. Additional annealing leads to a more uniform Mn distribution in the formed ZnS:Mn, Mg phosphor, which is accompanied by an increase in the intensity of the manganese photoluminescence band and quenching of the self-activated luminescence band.

Influence of Аl and Mn impurities on structural processes transformations in copper alloys

In the work on specific examples involving real copper-based alloys containing 14 weight %Al and 3 weight%Mn, describes the results of a study of the process of restoring the shape of a material that was defomatedaccording to the three-point bending scheme. The studies were carried out by measuring changes in thetemperature dependence of the electrical resistance and deflection of the sample, as well as by obtainingmicroelectronograms using an electron microscope. It is established that martensitic crystals that occur inhardened samples have a high density of packing defects and thin twins formed on the (121) γ´ plane.

Chemical State Analysis of the Periostracum in the Corbicula Clam Hatched in Lake Biwa

The periostracum of corbicula clams is a unique outermost organic layer secreted from the inner surface of the outer mantle. It records the environmental history of corbicula clams which inhabited Lake Biwa. Two types of corbicula clams, yellowish and blackish shells, were studied with X-ray fluorescence element mapping and S, Fe and Mn K-edge X-ray absorption fine structure (XAFS) spectroscopy. It was revealed that the blackish shells grow in the more reducing environment than the yellowish ones. Main constituent of the periostracum is protein-based material, such as cysteine and methionine. The blackish shells contain much higher amount of Fe and Mn impurities. Fe was accumulated as FeOOH along the growth lines. Sulfur exists exclusively as organic molecules with the functional groups of thiol (-SH), which is oxidized to form disulfide (-SS-) by exposure to the oxidizing environment.

Semiconductor–Metal Transition in Magnetic Semiconductor Compounds at High Pressure

The magnetic, transport, and magnetotransport properties of ferromagnetic Zn0.1Cd0.9GeAs2 + 10% MnAs and Zn0.1Cd0.9GeAs2 + 15% MnAs nanocomposites with a Curie temperature TC ≈ 310–312 K are studied at a high pressure up to 7 GPa and room temperature. The behavior of the magnetic and electronic properties under pressure points to a magnetic transformation and a semiconductor–metal transition, which occur at the same pressure (P ≈ 3.5 GPa). Both compositions exhibit pressure-induced magnetoresistance in the magnetic field range up to H = 5 kOe. As follows from an analysis of the experimental data, the magnetoresistance in the semiconductor–metal transition area is described by a standard p–d model, which takes into account the interaction of carrier spins and the magnetic moment localized at Mn impurities. A giant magnetoresistance is detected in this region: it is maximal in comparison with the magnetoresistance at atmospheric pressure (Δρxx/ρ0 < 1%) for the composition with 15% MnAs clusters. The appearance of enhanced magnetoresistance and the magnetic and electronic phase transformations are mainly caused by pressure-induced changes in the matrix.

Paramagnetic Mn Antisite Defects in Nanoceramics of Aluminum–Magnesium Spinel

The effect of structure and size parameters on the formation of intrinsic and impurity paramagnetic centers in nanoceramics of aluminum–magnesium spinel is studied. The studied samples (grain size ~30 nm) are obtained by thermobaric synthesis. Microcrystalline ceramics and MgAl2O4 single crystal are used as the reference samples. Characteristic paramagnetic centers of Mn2+ (hyperfine structure constant (HFS) A = 82 G) are present in both single crystal and microceramics. In the studied samples of nanoceramics in the initial state, both impurity Mn2+ and intrinsic F+ centers exist. Unlike the nanoceramics, the centers of F+ type in the reference sample appear only after the irradiation with accelerated electrons (130 keV). The parameters of Mn2+ centers in nanoceramics significantly differ on that in microceramics and single crystal. EPR signal of Mn2+ centers in nanoceramics is characterized by two anomalous constant HFS (A1 = 91.21 G, A2 = 87.83 G) caused by two types of octahedrally coordinated manganese ions ([Mn2+]$$_{{{\text{A}}{{{\text{l}}}^{{{\text{3 + }}}}}}}$$ antisite defects). The features of spectral parameters of manganese centers correlate with a decrease in the cell parameter of MgAl2O4 in the nanostructural state. The observed effects are interpreted based on the assumed scheme of [Mn2+]$$_{{{\text{A}}{{{\text{l}}}^{{{\text{3 + }}}}}}}$$ charge compensation by the aluminum antisite defect and F+ center.

Development of an AES based analytical method for the determination of trace metallic impurities in uranium silicide dispersion fuel: from precursors to end products

An analytical method was developed based on the D.C. arc carrier distillation atomic emission spectrometric (D.C. Arc AES) technique for determination of trace metallic impurities (Al, Ca, Co, Cr, Cu, Fe, Mg, Mn, Mo, Na, Ni, Si, Sn, Ti, V and Zn) in uranium silicide samples.

Парамагнитный резонанс ионов Cr-=SUP=-4+-=/SUP=- и Mn-=SUP=-2+-=/SUP=- в кристалле Li-=SUB=-2-=/SUB=-CaSiO-=SUB=-4-=/SUB=-

Tetragonal Cr4+ centers (3d2 electron configuration, spin S=1) in the Li2CaSiO4 crystal at different frequencies were detected and studied. The value of splitting at a zero magnetic field was determined. In the area where the positions of the two Cr4+ transitions coincide, the additional signal with inverse phase was observed. For uncontrolled impurity Mn2+ ions (S=I=5/2) the spin Hamiltonian parameters and localization are determined

Параметры полупроводниковых пленок ZnO, легированных 3d-примесями Mn, Fe

Abstract The effect of Fe and Mn impurities on the magnetic parameters of ZnO wide-gap semiconductor films produced by high-frequency sputtering with wide variations in the defect concentration is studied. The introduction of Mn and Fe magnetic impurities brings about the existence of a magnetically ordered state in the semiconductor matrix, with different positions of the axis of easy magnetization. In the case of doping with Mn, this axis lies perpendicularly to the film plane, and in the case of doping with Fe, this axis lies in the film plane.

Парамагнитные антисайт Mn-дефекты в нанокерамике алюмомагниевой шпинели

The influence of structural and dimensional factors on the formation of intrinsic and impurity paramagnetic centers in nanoceramics of aluminum-magnesium spinel is studied. The studied samples (with a grain size of 30 nm) were obtained by thermobaric synthesis. Microcrystalline ceramics and a MgAl2O4 single crystal were used as standards. The single crystal and microceramics contain characteristic Mn2+ paramagnetic centers (hyperfine structure constant (HFS) A = 82 G). In the studied nanoceramic samples in the initial state, both impurity Mn2+ and intrinsic F+ centers are detected. In contrast to nanoceramics, in reference samples centers of the F+ type appear only after irradiation with 130 keV by accelerated electrons. The parameters of the Mn2+ centers in nanoceramics differ significantly from those in microceramics and single crystals. For the Mn2+ center in nanoceramics, the EPR signal is characterized by two anomalous HFS constants (A1 = 91.21 G, A2 = 87.83 G) caused by two varieties of octahedrally coordinated manganese ions (anti-site defects [Mn2+]Al3+). The specific features of the spectral parameters of manganese centers correlate with a decrease in the lattice parameter of MgAl2O4 in the nanostructured state. The observed effects are interpreted based on the proposed charge compensation scheme of [Mn2+]Al3+ with an aluminum anti-site defect and an F+ center.

Thermodynamic phase diagram, magneto-optic and thermoelectric properties of the AlXN (X = Co, Fe and Mn) nano-sheet: DFT and TDDFT calculations

Based on the density functional theory, the phase diagrams, the structural, electronic, magneto-optic, and thermoelectric properties of the two-dimensional AlN structure are investigated with impurities Mn, Fe and Co in the position of Al and N atoms. Mechanical calculations show that all structures have a ground state point, and phase diagram calculations also confirm this. So that, for the negative chemical potentials of the Al atom, compounds that have impurity instead of the N atom are more stable, while at chemical potentials above −0.15 and positive regions, compounds that have impurities in the position of the Al atom are more stable. The electronic calculations show that in all the compounds, there is a magnetic behavior except in AlCoN–N ( N is replaced by Co). Hence, we see the emergence of magnetic gaps in two spins up and dn. The calculations of the magneto-optical Kerr effect show that the AlMnN-Al AlCoN–Al AlCoN–Al AlMnN-N combinations have appropriate angles of Kerr rotation at the UV edge, in particular, AlCoN–Al, in the range of 4 to 5 eV, we observed clockwise and counterclockwise rotations in Kerr angle, and also the most elasticity of light occurs.