Diluted magnetic semiconductors (DMSs) are expected to be key materials in future spintronic devices, since they are an excellent media in which charge and spin degrees of freedom are accommodated in a single matter, resulting in interesting magnetooptical, magnetoelectronic, and other properties. T...
Diluted magnetic semiconductors (DMSs) are expected to be key materials in future spintronic devices, since they are an excellent media in which charge and spin degrees of freedom are accommodated in a single matter, resulting in interesting magnetooptical, magnetoelectronic, and other properties. The unique properties of DMSs, such as field-effect control of ferromagnetism, efficient spin injection to produce circularly polarized light, and spin-dependant resonant tunneling, allow technological innovation in magnetoelectronics. Since the discovery of carbon nanotubes, the one-dimensional (1D) semiconductor nanostructures have attracted much attention as well-defined building blocks to fabricate nanoscale electronic and optoelectronic devices. The integration of 1D DMS nanostructures into electronics is particulary of importance in order to make real use of the advantages offered by the spins. We devote the most attention 1D DMS nanostructures have been synthesized using chemical vapor deposition methods. One of the crucial factors in the synthesis of 1D DMS nanostructures is the control of size, shape, growth direction, crystallinity, and composition. The structure, composition and magnetic properties were thoroughly investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-voltage TEM (HVEM) using 1.2 MV, scanning TEM (STEM) elemental mapping, energy-dispersive X-ray spectroscopy (EDX), high-resolution X-ray diffraction (XRD), Raman spectroscopy, and superconducting quantum interference (SQUID, Quantum Design) magnetometer. Chapter 1. We report Mn-doped GaN nanowires exhibiting ferromagnetism even at room temperature. The growth of single-crystalline wurtzite-structured GaN nanowires doped homogeneously with about 5 at. % Mn was achieved by chemical vapor deposition using the reaction of Ga/GaN/MnCl2 with NH3. The ferromagnetic hysteresis at 5 and 300 K and the temperature-dependent magnetization curves suggest the Curie temperature around 300 K. Negative magnetoresistance of individual nanowires was observed at the temperatures below 150 K. Chapter 2. We characterized the structure and magnetic properties of Mn-incorporated GaP nanowires synthesized by thermal evaporation of GaP/Mn powders. The nanowires consist of twin-crystalline zinc blende GaP grown with the [111] direction and doped with about 1 at. % Mn. They are often sheathed with the bumpy amorphous outerlayers containing high concentrations of Mn and O. The ferromagnetic hysteresis curves at 5 and 300 K and temperature-dependent magnetization provide evidence for the ferromagnetism with the Curie temperature higher than room temperature. Magnetic properties of individual nanowires have been measured, showing a large negative magnetoresistance equal to about -5% at 5 K. We suggest that the Mn doping of GaP nanowires would form a dilute magnetic semiconductor.
Diluted magnetic semiconductors (DMSs) are expected to be key materials in future spintronic devices, since they are an excellent media in which charge and spin degrees of freedom are accommodated in a single matter, resulting in interesting magnetooptical, magnetoelectronic, and other properties. The unique properties of DMSs, such as field-effect control of ferromagnetism, efficient spin injection to produce circularly polarized light, and spin-dependant resonant tunneling, allow technological innovation in magnetoelectronics. Since the discovery of carbon nanotubes, the one-dimensional (1D) semiconductor nanostructures have attracted much attention as well-defined building blocks to fabricate nanoscale electronic and optoelectronic devices. The integration of 1D DMS nanostructures into electronics is particulary of importance in order to make real use of the advantages offered by the spins. We devote the most attention 1D DMS nanostructures have been synthesized using chemical vapor deposition methods. One of the crucial factors in the synthesis of 1D DMS nanostructures is the control of size, shape, growth direction, crystallinity, and composition. The structure, composition and magnetic properties were thoroughly investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-voltage TEM (HVEM) using 1.2 MV, scanning TEM (STEM) elemental mapping, energy-dispersive X-ray spectroscopy (EDX), high-resolution X-ray diffraction (XRD), Raman spectroscopy, and superconducting quantum interference (SQUID, Quantum Design) magnetometer. Chapter 1. We report Mn-doped GaN nanowires exhibiting ferromagnetism even at room temperature. The growth of single-crystalline wurtzite-structured GaN nanowires doped homogeneously with about 5 at. % Mn was achieved by chemical vapor deposition using the reaction of Ga/GaN/MnCl2 with NH3. The ferromagnetic hysteresis at 5 and 300 K and the temperature-dependent magnetization curves suggest the Curie temperature around 300 K. Negative magnetoresistance of individual nanowires was observed at the temperatures below 150 K. Chapter 2. We characterized the structure and magnetic properties of Mn-incorporated GaP nanowires synthesized by thermal evaporation of GaP/Mn powders. The nanowires consist of twin-crystalline zinc blende GaP grown with the [111] direction and doped with about 1 at. % Mn. They are often sheathed with the bumpy amorphous outerlayers containing high concentrations of Mn and O. The ferromagnetic hysteresis curves at 5 and 300 K and temperature-dependent magnetization provide evidence for the ferromagnetism with the Curie temperature higher than room temperature. Magnetic properties of individual nanowires have been measured, showing a large negative magnetoresistance equal to about -5% at 5 K. We suggest that the Mn doping of GaP nanowires would form a dilute magnetic semiconductor.
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