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Scanning electron microscopy and high-resolution transmission electron microscopy measurements showed that the self-assembled (Ga0.8Mn0.2)As quantum wires (QWRs) grown on GaAs (100) substrates by using molecular beam epitaxy were straight crystals. The magnetization curve as functions of the magnetic field at 5 K indicated that the (Ga0.8Mn0.2)As QWRs were ferromagnetic, and the magnetization curve as a function of the temperature showed that the ferromagnetic transition temperature of the (Ga0.8Mn0.2)As diluted magnetic semiconductor (DMS) QWRs was as high as 350 K. Near-field scanning optical microscopy spectra showed the interband transitions of the (Ga0.8Mn0.2)As QWRs, indicative of the Mn atoms acting as substituents. These results indicate that the (Ga1-xMnx)As DMS QWRs with a high Mn concentration hold promise for potential application in spin optoelectric devices operating at room temperature. [ABSTRACT FROM AUTHOR]

(Ga1-xMnx)As thin films with both semiconducting and magnetic properties were formed by using Mn+ ion implantation and thermal annealing with a goal of producing (Ga1-xMnx)As with a high ferromagnetic transition temperature Tc. Energy dispersive x-ray fluorescence measurements showed that the Mn+-implanted neutron-transmutation-doped (NTD) GaAs samples were (Ga1-xMnx)As thin films, and photoluminescence spectra showed that the annealed (Ga1-xMnx)As thin films were p-type semiconductors. The magnetization curve as a function of the magnetic field showed that ferromagnetism existed in the (Ga1-xMnx)As thin films, and the magnetization curve as a function of the temperature showed that the Tc was ≈140 K. The present results indicate that high-Tc (Ga1-xMnx)As thin films with both semiconducting and magnetic properties can be formed from NTD-GaAs bulks by using Mn+ implantation and annealing method. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

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. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this work, pure and Ni-doped ZnO nanostructures (NSs) with different concentrations of Ni (2, 4, 6%) were successfully prepared via solution combustion method. The TEM photograph shows the formation of flake-like structures with the decrease in size of NSs as the dopant concentration is increased. XRD investigation shows the hexagonal wurtzite structure of doped and undoped ZnO nanostructures with a NiO peak (200) as secondary phase for 4 and 6% dopant concentration level. Broadening of spectra of ZnO around 480 cm in FTIR spectra is observed with the increase of dopant concentration. UV-Visible spectra show the increase in absorbance when the dopant level (Ni) is increase from 2 to 4% in ZnO and decrease in absorbance with further increase in dopant level to 6%. An increase in energy band gap is observed in Ni (6%)-doped ZnO due to due to the sp-d interactions taking place between the band electrons and the localised d electrons of Ni ions (Burstein-Moss effect). I-V characteristics reveal the increase in current with the increase in dopant level from 2 to 4% and decrease in current when the dopant level is further increased to 6% which is in agreement with the Burstein-Moss effect. [ABSTRACT FROM AUTHOR]