Mn Ion Implantation Research Articles

Above room temperature ferromagnetism in Mn-ion implanted Si

Above room temperature ferromagnetic behavior is achieved in Si through Mn ion implantation. Three-hundred-keV ${\mathrm{Mn}}^{+}$ ions were implanted to 0.1% and 0.8% peak atomic concentrations, yielding a saturation magnetization of $0.3\phantom{\rule{0.3em}{0ex}}\mathrm{emu}∕\mathrm{g}$ at $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for the highest concentration as measured using a SQUID magnetometer. The saturation magnetization increased by $\ensuremath{\sim}2\ifmmode\times\else\texttimes\fi{}$ after annealing at $800\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ for $5\phantom{\rule{0.3em}{0ex}}\mathrm{min}$. The Curie temperature for all samples was found to be greater than $400\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. A significant difference in the temperature-dependent remnant magnetization between the implanted p-type and n-type Si is observed, giving strong evidence that a Si-based diluted magnetic semiconductor can be achieved.

The effects of implanted nitrogen ions on the magnetic properties of Mn-implanted GaN

The effects of implanted N ions on the magnetic properties of Mn-implanted GaN were studied. The ferromagnetic signal increased when N ions were implanted into GaN prior to the implantation of Mn ions and annealed at 900°C. Synchrotron radiation photoemission spectroscopy revealed that the Ga−Mn magnetic phases contributing to ferromagnetic properties increased. Mn−N binary phases such as Mn6N258 and Mn3N2 decreased and sheet resistivity significantly increased, indicating a reduction of N-vacancies. Consequently, it is suggested that the enhancement of the ferromagnetic properties in (Mn+N)-implanted GaN originated from the decrease of N-vacancies and the increase of Ga−Mn magnetic phases.

Formation of ferromagnetic clusters in GaAs matrix and GaAs/AlGaAs superlattice through Mn ion implantation at two different temperatures

Different submicron ferromagnets are fabricated into GaAs and GaAs/AlGaAs superlattice through ion implantation at two different temperatures followed by thermal annealing. The structural and magnetic properties of the granular film are studied by an atomic force microscope, X-ray diffraction and alternating gradient magnetometer. By analyzing the saturation magnetization M s, remanence M r, coercivity H c and remanence ratio S q, it is confirmed that both MnGa and MnAs clusters are formed in the 350°C-implanted samples whereas only MnAs clusters are formed in the room-temperature implanted samples.

Nondestructive spectroscopic method to detect MnAs metallic nanocrystals in annealed GaAs:Mn

We report an optical spectroscopic method to monitor NiAs-type MnAs (α-MnAs) nanocrystals in (Ga,Mn)As diluted magnetic semiconductors. We utilize Mn ion implantation of low temperature (LT) GaAs epitaxial thin films followed by rapid thermal annealing (RTA) to yield embedded ferromagnetic α-MnAs nanoclusters in a GaAs:Mn matrix. As-implanted samples are paramagnetic and become ferromagnetic with Curie temperature of ∼320 K after RTA at 750 °C. No peaks of potential secondary phases could be observed in x-ray diffraction measurements. However, in optical spectra, the annealed samples show resonant absorption at 0.9 eV photon energy, due to resonant surface plasma oscillation of spherical metallic phases embedded in LT GaAs. Since the absorption peak position in the photon energy has a direct relation to the value of the plasma frequency of metallic inclusions, the metallic clusters in LT GaAs are identified as α-MnAs nanocrystals by comparing them with simulations based on Maxwell–Garnett theory. We suggest that this optical method can be applied to various granular systems and diluted magnetic semiconductors as a nondestructive way to detect and quantify metallic nanoclusters.

Effects of High Dose Ni, Fe, Co, and Mn Implantation into SnO[sub 2

The effects of high dose (3 3 1016 cm22) implantation of Ni, Fe, Co, or Mn ions into bulk, single-crystal SnO2 substrates carried out at substrate temperature of ;350 C to avoid amorphization of the implanted region on the magnetic properties of the material are reported. X-ray diffraction showed no evidence of secondary phase formation in the SnO2 . The Mn-implanted samples remained paramagnetic, as also reported for samples doped during thin film growth, but the Fe, Co-, and Ni-implanted SnO2 showed evidence of hysteresis with approximate Curie temperatures of ;120 K ~Co and Cr! or 300 K ~Fe!. The carrier density in the implanted region appears to be too low to support carrier-mediated origin of the ferromagnetism and formation of bound magnetic polarons may be one explanation for the observed magnetic properties. The much reduced Curie temperature seen in Co-implanted SnO2 compared to material doped during pulsed laser deposition suggests the residual implant damage degrades the magnetic properties.

The magnetic and structure properties of room-temperature ferromagnetic semiconductor (Ga,Mn)N

Diluted magnetic semiconductor (Ga,Mn)N were prepared by the implantation of Mn ions into GaN/Al 2O 3 substrate. Clear X-ray diffraction peak from (Ga,Mn)N is observed. It indicates that the solid solution (Ga,Mn)N phase was formed with the same lattice structure as GaN and different lattice constant. Magnetic hysteresis-loops of the (Ga,Mn)N were obtained at room temperature (293 K) with the coercivity of about 2496.97 A m −1.

Magnetic properties of Mn-implanted AlGaP alloys

Ion implantation of Mn at concentrations of 1–5 at. % was performed in AlxGa1−xP:C (x=0, 0.24, 0.38, and 0.54) epilayers grown by gas source molecular beam epitaxy. Ferromagnetic-like ordering at 300 K was observed for Mn doses up to 3 at. % for all Al subfractions in superconducting quantum interference device measurements. The calculated magnetic moment was found to peak at 3 at. % Mn in plots of magnetization versus Mn for all four Al subfractions. For a given Mn concentration, the magnetic moment was found to initially increase then decrease in plots of magnetization versus Al subfraction. Structural characterization revealed the presence of the Mn2P and Mn3Ga phases in Al0.54Ga0.46P:C layers implanted with 5 at. % Mn, while no second phases were observed in any other combinations of Al and Mn. A substantial increase in magnetic ordering temperature predicted by theory for AlxGa1−xP:C films compared to GaP:C films with Mn incorporation was not observed.

Ferromagnetic semiconductors based upon AlGaP

Ion implantation of Mn or Cr at concentrations of 1–5 at. % were performed in AlxGa1−xP (x=0.24,0.38) epilayers grown by gas source molecular beam epitaxy. Ferromagnetic-like ordering above 100 K for Cr and 300 K for Mn was observed in superconducting quantum interference device measurements. Structural characterization revealed no second phases that could influence the measured magnetic properties. As the AIP mole fraction in the AlxGa1−xP layers increased, the magnetic ordering temperatures were generally observed to increase, while the calculated magnetic moment decreased. Mn appears to be a more promising choice than Cr for high temperature ferromagnetism in AlGaP.

(Ga,Mn,N) compounds growth with mass-analyzed low energy dual ion beam deposition

The (Ga,Mn,N) samples were grown by the implantation of low-energy Mn ions into GaN/Al 2O 3 substrate at different elevated substrate temperatures with mass-analyzed low-energy dual ion beam deposition system. Auger electron spectroscopy depth profile of samples grown at different substrate temperatures indicates that the Mn ions reach deeper in samples with higher substrate temperatures. Clear X-ray diffraction peak from (Ga,Mn)N is observed in samples grown at the higher substrate temperature. It indicates that under optimized substrate temperature and annealing conditions the solid solution (Ga,Mn)N phase in samples was formed with the same lattice structure as GaN and different lattice constant.

Ferromagnetic Ga1−xMnxAs produced by ion implantation and pulsed-laser melting

We demonstrate the formation of ferromagnetic Ga1−xMnxAs films by Mn ion implantation into GaAs followed by pulsed-laser melting. Irradiation with a single excimer laser pulse results in the epitaxial regrowth of the implanted layer with Mn substitutional fraction up to 80% and effective Curie temperature up to 29 K for samples with a maximum Mn concentration of x≈0.03. A remanent magnetization persisting above 85 K has been observed for samples with x≈0.10, in which 40% of the Mn resides on substitutional lattice sites. We find that the ferromagnetism in Ga1−xMnxAs is rather robust to the presence of structural defects.

Maskless Mn implantation in GaAs using focused Mn ion beam

Fifteen kiloelectronvolts focused Mn ion beam was implanted on molecular beam epitaxy-grown Si-δ-doped GaAs which was mesa-etched to form Hall-bar geometry and annealed at 840 °C for 10 s in hydrogen and argon mixed gas ambient. Au–Si–Mn liquid metal alloy ion source was fabricated to perform both Mn and Si ion implantation. From the Hall resistance measurement at 77 K, non-linear behavior and hysteresis were observed in the Hall resistance in the Mn implanted region. The present result indicates that a ferromagnetic layer is formed in GaAs by the Mn ion implantation.

Structural and magnetic properties of MnAs nanoclusters formed by Mn ion implantation in GaAs

Ferromagnetic (FM) nanostructures embedded in semiconductors are attracting interest because their physical properties could be used in new devices such as memories, sensors or more generally involving “spintronics”. In this work, we present results on the synthesis and the characterization of nanosized MnAs ferromagnets buried in GaAs. These nanocrystals can be formed either by single Mn implantation or by Mn+As co-implantation at room temperature into GaAs wafers followed by thermal annealing. High-resolution transmission electron microscopy and diffraction analysis show that the MnAs precipitates exhibit the regular hexagonal structure with a 3 m orientation relationship with respect to the matrix. The mean diameters of the nanocrystals range from 9 to 13 nm depending on the annealing conditions. Magnetization measurements by superconducting quantum interference device magnetometry reveal an FM state. Upon warming, a progressive transition to a superparamagnetic state is evidenced, probably due to the distribution of individual blocking temperatures, resulting both from the size distribution of the nanocrystals and from dipolar interactions. Curie temperatures in the range of 360 K are measured, significantly higher than for bulk MnAs.

Properties of Mn-Implanted BaTiO[sub 3], SrTiO[sub 3], and KTaO[sub 3

Mn ion implantation into single-crystal BaTiO 3 (K). SrTiO 3 , or KTaO 3 (Ca) was investigated for its effects on the magnetic properties of these materials. Following annealing at 700°C, the Mn implantation was found to induce ferromagnetic behavior for most of the concentration range investigated. For BaTiO 3 , Mn implantation produced magnetic ordering temperatures near 300 K with coercivities ≤70 Oe. The magnetization/temperature plots showed a non-Brillouin-shaped curve. No secondary phases were detected by high resolution X-ray diffraction. The results are consistent with theoretical predictions for transition metal doping of BaTiO 3 . The same basic trends were observed for both SrTiO 3 and KTaO 3 , with the exception that at high Mn concentrations (∼5 atom %) the SrTiO3 was no longer ferromagnetic.

Room-temperature ferromagnetic semiconductor MnxGa1xSb

Ferromagnetic semiconductor MnxGa1-xSb single crystals were fabricated by Mn-ions implantation, deposition, and the post annealing. Magnetic hysteresis-loops in the MnxGa1-xSb single crystals were obtained at room temperature (300 K). The structure of the ferromagnetic semiconductor MnxGa1-xSb single crystal was analyzed by Xray diffraction. The distribution of carrier concentrations in MnxGa1-xSb was investigated by electrochemical capacitance- voltage profiler. The content of Mn in MnxGa1-xSb varied gradually from x = 0.09 near the surface to x = 0 in the wafer inner analyzed by X-ray diffraction. Electrochemical capacitance-voltage profiler reveals that the concentration of p-type carriers in MnxGa1-xSb is as high as 1 1021 cm-3, indicating that most of the Mn atoms in MnxGa1-xSb take the site of Ga, and play a role of acceptors.

Preparation and characterization of room-temperature ferromagnetism GaMnN based on ion implantation

This paper reports the fabrication of GaMnN ferromagnetic semiconductor on GaN substrate by high-dose Mn ion implantation. Both the structural and optical properties for Mn+-implanted GaN material were studied by X-ray diffraction, Raman scattering and photoluminescence. the results reveal that the implanted manganese incorporates on Ga site and GaMnN ternary phase is formed in the substrate. The magnetic behavior has been characterized by superconducting quantum interference device. The material shows room-temperature ferromagnetism. The temperature-dependent magnetization indicates different mechanism for ferromagnetism in Mn+-implanted GaN.

Unconventional carrier-mediated ferromagnetism above room temperature in ion-implanted (Ga, Mn)P:C.

Ion implantation of Mn ions into hole-doped GaP has been used to induce ferromagnetic behavior above room temperature for optimized Mn concentrations near 3 at. %. The magnetism is suppressed when the Mn dose is increased or decreased away from the 3 at. % value, or when n-type GaP substrates are used. At low temperatures the saturated moment is on the order of 1 Bohr magneton, and the spin wave stiffness inferred from the Bloch-law T(3/2) dependence of the magnetization provides an estimate T(c)=385 K of the Curie temperature that exceeds the experimental value, T(c)=270 K. The presence of ferromagnetic clusters and hysteresis to temperatures of at least 330 K is attributed to disorder and proximity to a metal-insulating transition.

Magnetic effects of direct ion implantation of Mn and Fe into p-GaN

In p-GaN implanted with Mn (3 × 1016cm-2 at 250 keV), the material after annealing shows ferromagnetic properties below 250 K. Cross-sectional transmission electron microscopy (TEM) revealed the presence of platelet structures with hexagonal symmetry. These regions are most likely GaxMn1-xN, which produce the ferromagnetic contribution to the magnetization. In p-GaN implanted with Fe, the material after annealing showed ferromagnetic properties at temperatures that were dependent on the Fe dose, but were below 200 K in all cases. In these samples, TEM and diffraction analysis did not reveal any secondary phase formation. The results for the Fe implantation are similar to those reported for Fe doping during epitaxial growth of GaN.

(Ga,Mn,As) compounds grown on semi-insulating GaAs with mass-analyzed low energy dual ion beam deposition

The (Ga,Mn,As) compounds were obtained by the implantation of Mn ions into semi-insulating GaAs substrate with mass-analyzed low energy dual ion beam deposition technique. Auger electron spectroscopy depth profile of a typical sample grown at the substrate temperature of 250°C showed that the Mn ions were successfully implanted into GaAs substrate with the implantation depth of 160 nm. X-ray diffraction was employed for the structural analyses of all samples. The experimental results were greatly affected by the substrate temperature. Ga 5.2Mn was obtained in the sample grown at the substrate temperature of 250°C. Ga 5.2Mn, Ga 5Mn 8 and Mn 3Ga were obtained in the sample grown at the substrate temperature of 400°C. However, there is no new phase in the sample grown at the substrate temperature of 200°C. The sample grown at 400°C was annealed at 840°C. In this annealed sample Mn 3Ga disappeared, Ga 5Mn 8 tended to disappear, Ga 5.2Mn crystallized better and a new phase of Mn 2As was generated.

Enhanced positive magnetoresistance effect in GaAs with nanoscale magnetic clusters

The enhanced positive magnetoresistance effect has been observed in GaAs containing nanoscale magnetic clusters. The ferromagnetic metallic clusters were embedded into GaAs by Mn ion implantation and rapid thermal annealing. Positive magnetoresistance in these structures has been observed and attributed to the enhanced geometric magnetoresistance effect in inhomogeneous semiconductors with metallic inclusions. The additional enhancement of positive magnetoresistance under light illumination is due to the higher mobility of photoexcited electrons in comparison with the mobility of holes in p-type GaAs prepared by Mn ion implantation.

Photo-enhanced Magnetoresistance Effect in GaAs with Nanoscale Magnetic Clusters

Enhanced positive magnetoresistance effect under light illumination has been observed in GaAs containing nanoscale magnetic clusters. The ferromagnetic clusters were embedded into GaAs by using Mn ion implantation and rapid thermal annealing. Positive magnetoresistance in these structures has been observed and attributed to the scattering of charge carriers by the nanomagnet-dipole field. The enhancement of positive magnetoresistance under light illumination is due to a higher mobility of photoexcited electrons in comparison with the mobility of holes in p-type GaAs prepared by Mn ion implantation.