Mn Ion Implantation Research Articles

Diamond‐Based Supercapacitors with Ultrahigh Cyclic Stability Through Dual‐Phase MnO2‐Graphitic Transformation Induced by High‐Dose Mn‐Ion Implantation

AbstractWhile occasionally being able to charge and discharge more quickly than batteries, carbon‐based electrochemical supercapacitors (SCs) are nevertheless limited by their simplicity of processing, adjustable porosity, and lack of electrocatalytic active sites for a range of redox reactions. Even SCs based on the most stable form of carbon (sp3 carbon/diamond) have a poor energy density and inadequate capacitance retention during long charge/discharge cycles, limiting their practical applications. To construct a SC with improved cycling stability/energy density Mn‐ion implanted (high‐dose; 1015–1017 ions cm−2) boron doped diamond (Mn‐BDD) films have been prepared. Mn ion implantation and post‐annealing process results in an in situ graphitization (sp2 phase) and growth of MnO2 phase with roundish granular grains on the BDD film, which is favorable for ion transport. The dual advantage of both sp2 (graphitic phase) and sp3 (diamond phase) carbons with an additional pseudocapacitor (MnO2) component provides a unique and critical function in achieving high‐energy SC performance. The capacitance of Mn‐BDD electrode in a redox active aqueous electrolyte (0.05 M Fe(CN)63‐/4− + 1 M Na2SO4) is as high as 51 mF cm−2 at 10 mV s−1 with exceptional cyclic stability (≈100% capacitance even after 10 000 charge/discharge cycles) placing it among the best‐performing SCs. Furthermore, the ultrahigh capacitance retention (≈80% retention after 88 000 charge/discharge cycles) in a gel electrolyte containing a two‐electrode configuration shows a promising prospect for high‐rate electrochemical capacitive energy storage applications.

Nanodiamonds Doped with Manganese for Applications in Magnetic Resonance Imaging.

Nanodiamonds (NDs) are emerging with great potential in biomedical applications like biomarking through fluorescence and magnetic resonance imaging (MRI), targeted drug delivery, and cancer therapy. The magnetic and optical properties of NDs could be tuned by selective doping. Therefore, we report multifunctional manganese-incorporated NDs (Mn-NDs) fabricated by Mn ion implantation. The fluorescent properties of Mn-NDs were tuned by inducing the defects by ion implantation and enhancing the residual nitrogen vacancy density achieved by a two-step annealing process. The cytotoxicity of Mn-NDs was investigated using NCTC clone 929 cells, and the results revealed no cytotoxicity effect. Mn-NDs have demonstrated dual mode contrast enhancement for both T 1- and T 2-weighted in vitro MR imaging. Furthermore, Mn-NDs have illustrated a significant increase in longitudinal relaxivity (fivefold) and transversal relaxivity (17-fold) compared to the as-received NDs. Mn-NDs are employed to investigate their ability for in vivo MR imaging by intraperitoneal (ip) injection of Mn-NDs into mice with liver tumors. After 2.5 h of ip injection, the enhancement of contrast in T 1- and T 2-weighted images has been observed via the accumulation of Mn-NDs in liver tumors of mice. Therefore, Mn-NDs have great potential for in vivo imaging by MR imaging in cancer therapy.

Structural, optical and half-metallic properties of Mn and As co-implanted ZnO thin films

In this work, we use ion implantation to implant Mn ions and As ions into the ZnO films prepared by molecular beam epitaxy.The surface morphology and crystalline structure of ZnO thin films are investigated by X-ray diffraction, atomic force microscopy and Raman spectroscopy. First-principles calculations discover the half-metallic property of the ZnO films implanted with Mn ions. The effects of Mn ions and As ions implantation on the absorption edges, refractive index (n), extinction coefficient (k) and dielectric constant of ZnO films are studied by transmission spectra, absorption spectroscopy and spectroscopic ellipsometric technique. From the spectroscopic ellipsometry (SE), the n and k of the films have increased after ion implantation. Due to the half-metallic properties of the Mn-implanted ZnO film, the variation trend of the peaks of n and k with wavelength is much gentler than the peak of unimplanted ZnO film. The dielectric constant measured by SE and the results of photoluminescence spectra reveal that the electron transition of ZnO films is weakened by Mn ions implantation. The results provide a new direction for the design and optimization of optoelectronic devices based on ZnO thin films with semi-metallic properties.

Exploring the corrosion behavior of Mn-implanted biomedical Mg

Many surface modification technologies have been developed on biomedical magnesium (Mg) and its alloys to expand potential clinical applications. In this study, the bio-safe manganese (Mn) element was implanted into the biomedical Mg surface by a metal vapor vacuum arc (MEVVA) technique. In the Mn-implanted layer, Mn existed in the form of both metallic and oxidized states. Besides, Mn ion implantation changed the corrosion behavior of biomedical Mg in Hank’s solution. At the initial stage of immersion, the corrosion rate was accelerated owing to the galvanic couple between metallic Mn and Mg, and micro-scale galvanic corrosion was uniformly distributed on surfaces. With the immersion time prolonging, Mn-implanted Mg displayed enhanced anti-corrosive property, presenting as a change from corrosion prone to corrosion resistance. On the one hand, the anti-corrosive and uniform Ca, P-containing products were formed on the corroded surface based on uniformly-distributed micro-scale pitting corrosion. On the other hand, the metallic Mn tended to be oxidized to stable Mn oxide so that galvanic corrosion was retarded. This research attempts to explore the effect of Mn ion implantation on the corrosion behavior of biomedical Mg, and offers new insight into novel surface modifications of biomedical Mg devices for long-time implantation.

Fabrication and characterization of Mn-implanted GaN layers followed by annealing

We report the effect of Mn incorporation on the structural and optical properties of GaN grown on a sapphire substrate in a plasma-enhanced molecular-beam epitaxy system followed by Mn ion implantation and annealing. The crystalline quality and phase purity were determined by high-resolution X-ray diffraction (XRD). The XRD results indicated that no macroscopic second phases were present in the Mn-implanted GaN layer after the annealing process. High-resolution transmission microscopy and energy dispersive X-ray spectroscopy revealed that the as-grown GaN epilayer and Mn-implanted GaN layer after annealing were single crystals with a hexagonal wurtzite structure, and they grew with a c-axis orientation perpendicular to the sapphire substrate. The Raman and photoluminescence spectra showed that the Mn-implanted GaN layer fabricated with a Mn ion dose of 5 × 1015 cm−2 followed by annealing at 800 °C for 30 min had higher crystalline quality than the Mn-implanted GaN layers fabricated with Mn ion doses of 5 × 1015 and 2 × 1016 cm−2 followed by annealed at 900 °C for 30 and 80 min.

Manganese ion implanted ultrananocrystalline diamond films: Optical and electrical characterization

We report the optical and electrical properties of high-dose (1015–1017 ions/cm2) Mn-ion implanted ultrananocrystalline diamond (Mn-UNCD) films. Mn-ion implantation and post-annealing of UNCD films lead to the formation of Mn-related color centers, characterized in Mn-UNCD films by their zero phonon line emissions at 621.2 nm and phonon sidebands at 611.2 nm and 630.3 nm. Raman spectra of Mn-UNCD films indicated amorphization via high-dose Mn-ion implantation and that the annealing process results in graphitization of the films. The Mn-UNCD film implanted with the Mn-ion dose of 1017 ions/cm2 exhibits a conductivity of 122.25 (Ω cm)−1, as well as enhanced field electron emission (FEE) properties such as a turn-on field of 10.67 V/μm and a FEE current density of 0.85 mA/cm2.

XAS and TEM studies on ferromagnetic GeMn prepared by Mn ion implantation and helium ion beam induced epitaxial crystallization

In this study, we prepared a p-type Ge thin film and then implanted Mn ions in it at room temperature. P-type Ge thin film was made by gallium ion implantation in to an n-type Ge substrate to provide additional hole carriers. Mn ions were implanted into the same layer with Ga ions. Helium ion beam induced epitaxial crystallization with 2 MeV was used to growth GeMn thin films. The results show the beam annealed GeMn sample has been regrowth and has magnetoresistance.

Ferromagnetic (In,Ga,Mn)As films prepared by ion implantation and pulsed laser melting

In the present work, we show the preparation of (In,Ga,Mn)As films with different Ga concentration by Mn ion implantation and pulsed laser melting. All films are confirmed to be well recrystallized by Rutherford backscattering spectrometry/channeling and to be ferromagnetic by magnetometry measurements, respectively. Their Curie temperatures depend on the Ga concentration. Our results show the perspective of ion implantation in the preparation of different III-Mn-V quaternary alloys as new members of diluted ferromagnetic semiconductors.

EXAFS study on local structure of GaMnAs thin film made by Mn ion implantation following with ion beam induced epitaxial crystallization

In this study, we used Mn ion implantation following with helium ion irradiation to prepare GaMnAs thin film. Extended X-ray absorption fine structure, and X- ray absorption spectrum were applied to analyze the crystalline of Mn implanted GaAs layer. And the results showed implanted Mn ions stand on the substitutional site of Ga ions of GaAs lattice. Also from X-ray absorption spectrum, we confirmed the electronic valence state of Mn ions in the implanted layer were 2+.

Effects of thermal annealing on structural and magnetic properties of Mn ions implanted AlInN/GaN films

In the search of functional diluted magnetic semiconductors, a study of effects of Mn ions implantation on structural and magnetic properties of AlInN/GaN/sapphire films is reported. Mn ions at 200 keV were implanted into the layers at three doses 5 × 1014 cm−2, 5 × 1015 cm−2 and 5 × 1016 cm−2. The as-implanted samples were thermally annealed and investigated by using X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS) and vibrating sample magnetometry (VSM). The structural analysis of the samples indicated that the sample implanted at dose of 5 × 1014 cm−2 and thermally annealed at 750 °C exhibited good crystalline recovery. The ferromagnetism of the samples was investigated by recording magnetization as a function of applied magnetic field. The magnetic characterizations exhibited well shaped hysteresis at room temperature which indicates presence of high temperature ferromagnetism in the samples. The findings of this work pointed out that AlInN/GaN samples implanted with Mn ions at dose of 5 × 1016 cm−2 and annealing at 750 °C exhibited maximum magnetization. On the basis of first principles calculations, it is predicted that p–d interaction is the mechanism of ferromagnetic ordering in the material.

Effects of Mn Ion Implantation on XPS Spectroscopy of GaN Thin Films

Gallium nitride (GaN) thin film was deposited onto a sapphire substrate and then implanted with 250 keV Mn ions at two different doses of 2 × 1016 ions/cm2 and 5 × 1016 ions/cm2. The as-grown and post-implantation-thermally-annealed samples were studied in detail using x-ray photoelectron spectroscopy (XPS). The XPS peaks of Ga 3d, Ga 2p, N 1s, Mn 2p and C 1s were recorded in addition to a full survey of the samples. The doublet peaks of Ga 2p for pure GaN were observed blue-shifted when compared with elemental Ga, and appeared further shifted to higher energies for the implanted samples. These observations point to changes in the bonds and the chemical environment of the host as a result of ion implantation. The results revealed broadening of the N 1s peak after implantation, which is interpreted in terms of the presence of N-Mn bonds in addition to N-Ga bonds. The XPS spectra of Mn 2p recorded for ion-implanted samples indicated splitting of Mn 2p 1/2 and Mn 2p 3/2 peaks higher than that for metallic Mn, which helps rule out the possibility of clustering and points to substitutional doping of Mn. These observations provide a framework that sheds light on the local environment of the material for understanding the mechanism of magnetic exchange interactions in Mn:GaN based diluted magnetic semiconductors.

Interplay between localization and magnetism in (Ga,Mn)As and (In,Mn)As

Ion implantation of Mn combined with pulsed laser melting is employed to obtain two representative compounds of dilute ferromagnetic semiconductors (DFSs): Ga1-xMnxAs and In1-xMnxAs. In contrast to films deposited by the widely used molecular beam epitaxy, neither Mn interstitials nor As antisites are present in samples prepared by the method employed here. Under these conditions the influence of localization on the hole-mediated ferromagnetism is examined in two DFSs with a differing strength of p-d coupling. On the insulating side of the transition, ferromagnetic signatures persist to higher temperatures in In1-xMnxAs compared to Ga1-xMnxAs with the same Mn concentration x. This substantiates theoretical suggestions that stronger p-d coupling results in an enhanced contribution to localization, which reduces hole-mediated ferromagnetism. Furthermore, the findings support strongly the heterogeneous model of electronic states at the localization boundary and point to the crucial role of weakly localized holes in mediating efficient spin-spin interactions even on the insulator side of the metal-insulator transition.

Defect formation and its effect on electronic structure and magnetic properties of GaN:Mn films

GaN:Mn thin films were fabricated by implanting Mn ions into Mg-doped GaN epilayer. X-ray diffraction study reveals that all the samples are in single phase wurtzite crystalline structure. Raman spectra exhibit additional excitations attributed to the vibrational mode of defects caused by Mn ion implantation and the Mn related local vibrational mode in the vicinity of E2high. The X-ray photoelectron spectroscopy results indicate that the Mn ions were successfully incorporated into the GaN host lattice by substituting the Ga sites. The magnetization curve as a function of the magnetic field at 300K indicates that room ferromagnetisms exist in GaN:Mn thin films. The effect of vacancy defect on the magnetic properties of MnMg co-doped GaN has been studied by first principles calculations. Based upon experimental and theoretical results, it is believed that the alteration of ferromagnetism with annealing temperature is directly related to the variation of magnetic exchange interaction with microstructure in this material system.

Strain and optical characteristics study of ferromagnetic GaMnAs fabricated by ion beam induced epitaxial crystallization

Abstract In this study, we use a semi-insulating GaAs wafer to prepare a GaMnAs thin film by Mn ion implantation and subsequent helium ion beam induced epitaxial crystallization. In addition, we use different helium energies to anneal the GaMnAs thin films. The regrown GaMnAs thin films are measured using high-resolution X-Ray diffraction, Raman scattering and spectrophotometry to analyze the crystal structures and optical properties. It is found that the GaMnAs thin films remain fully strained. All experimental results indicate that the GaMnAs thin film is formed after the ion beam induced epitaxial crystallization annealing.

Depth distribution of Mn in Mn doped GaAs using secondary ion mass spectrometry

Secondary ion mass spectrometry (SIMS) was used for depth distribution analysis of Mn in GaAs formed by ion implantation of Mn in GaAs single crystal wafers at an implant energy of 300 keV, followed by laser pulse heating to anneal out the radiation damage. Mn doped GaAs, due to its ferromagnetic behavior, has potential applications in spintronic devices. Knowledge of the quantitative depth distribution, diffusion and segregation of these dopant atoms in the host material are necessary for fabrication of these devices. The depth distribution of Mn was carried out using oxygen and cesium primary ion beams at various impact energies. The obtained depth profiles of Mn demonstrated that Mn was uniformly distributed in as-implanted and single shot laser annealing samples, whereas in case of double shot annealing, segregation effect of Mn atoms toward the decaying trail of the distribution curve was observed, thanks to extremely high detection sensitivity of SIMS. Relative sensitivity factors of Mn in GaAs were determined for oxygen and cesium primary ion beams using as-implanted samples at various impact energies under the optimized analysis conditions, retaining the high depth resolution. Surface distribution of Mn was carried out using SIMS, which revealed uniform lateral distribution of Mn in as-implanted as well as laser annealed samples.

Anomalous magnetic properties of Mn-implanted InN thin films

Anomalous magnetic properties of C-axis-oriented Mn-implanted InN thin films on GaN/sapphire substrates are reported. X-ray diffraction analysis revealed Mn-implanted InN films of a high-quality crystal phase with wurtzite structure. All samples show n-type conductivity by Hall measurements. The un-implanted InN/GaN/Al2O3 sample with a carrier concentration of 1.6×1021cm−3 (n2D=8×1016cm−2) exhibits increasing magnetization with decreasing temperature and did not appear superconductive above 1.8K. After Mn-ion implantation, the appearance of the Meissner effect with superconducting onset temperature near 2.4K was observed. The superconducting volume fraction χ is near 36% at 2.2K. Moreover, type-II behavior was further characterized by field-dependent magnetization measurement.

Local structure study of GeMn recrystallization process by helium ion beam-induced epitaxial crystallization

In this study, GeMn thin films were fabricated by implantation of Mn ions at room temperature. Post-annealing was performed using 2MeV of He+ ion irradiation. The recrystallization phenomena of the GeMn thin films were analyzed by Raman scattering. High-resolution transmission electron microscopy was also used to characterize the recrystallization process before and after ion beam annealing. A structure phase transition-like behavior of the recrystallization process of GeMn thin films was observed in the Raman spectra.

A comprehensive study of the magnetic, structural, and transport properties of the III-V ferromagnetic semiconductor InMnP

The manganese induced magnetic, electrical, and structural modification in InMnP epilayers, prepared by Mn ion implantation and pulsed laser annealing, are investigated in the following work. All samples exhibit clear hysteresis loops and strong spin polarization at the Fermi level. The degree of magnetization, the Curie temperature, and the spin polarization depend on the Mn concentration. The bright-field transmission electron micrographs show that InP samples become almost amorphous after Mn implantation but recrystallize after pulsed laser annealing. We did not observe an insulator-metal transition in InMnP up to a Mn concentration of 5 at. %. Instead all InMnP samples show insulating characteristics up to the lowest measured temperature. Magnetoresistance results obtained at low temperatures support the hopping conduction mechanism in InMnP. We find that the Mn impurity band remains detached from the valence band in InMnP up to 5 at. % Mn doping. Our findings indicate that the local environment of Mn ions in InP is similar to GaMnAs, GaMnP, and InMnAs; however, the electrical properties of these Mn implanted III-V compounds are different. This is one of the consequences of the different Mn binding energy in these compounds.

Enhancement of La0.6Sr0.4Co0.2Fe0.8O3-δ Surface Exchange through Ion Implantation

La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) has been demonstrated to be one of the best performing mixed ionic-electronic conductors (MIEC) for SOFC cathode materials. Surface exchange on LSCF, however, limits oxygen transport and performance. We investigated surface modified LSCF, by Mn ion implantation, for an enhanced surface oxygen exchange rate while maintaining LSCFs oxygen ion conductivity through the bulk. Various implantation energies and ion concentrations were used to create samples with different Mn-ion depth profiles. The oxygen transport properties, chemical diffusion coefficient (Dchem) and effective chemical surface exchange coefficient (kchem), were characterized by electrical conductivity relaxation (ECR), using DC four-point probe measurements during the oxygen re-equilibration process. The changes of kchem for different Mn doping levels and ion acceleration energies determined with ECR are compared with surface configurations obtained using X-ray photoelectron spectroscopy. The Mn ion implanted LSCF samples show an enhanced kchem, improving the overall oxygen reduction reaction for the LSCF cathode material. Possible factors for the increase in surface exchange for the Mn implanted LSCF samples are discussed.

Synthesis and characterization of MnAs and MnP nanoclusters embedded in III–V semiconductors

We report on a systematic study of the synthesis and magnetism of hybrid ferromagnetic semiconductors comprised of MnAs and MnP nanoclusters embedded in GaAs and InP matrices, respectively. Samples were prepared by Mn-ion implantation followed by millisecond-range flash lamp annealing. X-ray diffraction and Auger electron spectroscopy results confirm the formation of MnAs nanoclusters of sizes 150 ± 50 nm. Ferromagnetic properties of MnAs:GaAs (MnP:InP) hybrid systems are studied by magnetic force microscopy and superconducting quantum interference device magnetometry. We show that the magnetization at saturation and the ferromagnetic transition temperature , of MnAs:GaAs depend on the Mn-concentration and on the annealing energy density. While in the case of MnP:InP they are independent of the annealing energy density used. Ferromagnetism in such hybrid systems (ferromagnet–semiconductor) above 300 K makes them very attractive for applications in spintronic devices.