Manganese and cobalt-doped ZnO have been produced using a modified melt-growth technique. X-ray diffraction measurements indicate that the samples are high-quality single crystals with −2 full width at half maximum values of 78 arc sec for the undoped ZnO and 252 arc sec for Zn 1−x Mn x O ͑x = 0.05͒. The lattice parameter of the Zn 1−x Mn x O was observed to increase with Mn concentration. Transmission measurements showed systematic variations dominated by absorption from interatomic Mn 2+ and Co 2+ transitions. No evidence of diluted magnetic semiconductor mean-field ferromagnetic behavior was observed in any of these nominally noncarrier-doped samples. The magnetic properties instead showed paramagnetic behavior for Zn 1−x Mn x O dominated by an antiferromagnetic Mn-Mn exchange interaction at low temperatures. Zn 1−x Co x O showed hysteresis that was attributed to superparamagnetic Co clusters embedded in a diamagnetic ZnO matrix. It has been shown that in the bulk single-crystal form, intrinsic and noncarrier-doped Zn 1−x TM x O is not ferromagnetic; thus creative processing and doping techniques are necessary to achieve practical ferromagnetism in these materials.

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We report the growth and characterization of gadolinium oxide films deposited on Si͑100͒ and fused quartz in the temperature range of 450-800°C by a low-pressure metalorganic chemical vapor deposition technique using a ␤-diketonate complex of gadolinium as the precursor. The x-ray diffractometry study of the films reveals that, irrespective of the growth temperature, the films grown on fused quartz (i.e., an amorphous substrate) and silicon (i.e., a single-crystal substrate) comprise the cubic Gd 2 O 3 phase with a (111) texture. However, the films grown on fused quartz at higher temperatures also show the presence of the monoclinic phase of Gd 2 O 3 . The growth of strongly oriented films on fused quartz has been understood on the basis of minimization of the surface energy. The scanning electron microscopy and atomic force microscopy studies reveal that the films grown at or above 525°C are densely packed and grainy. Optical properties of the films, as studied by ultraviolet (UV)-visible spectrophotometry and Fourier transform infrared spectroscopy, are found to depend strongly on the chemical vapor deposition condition. The analyses reveal further that the films grown at or above 500°C are free of heteroatoms, i.e., C, N, and H. The optical band gap of the films is in the range of 5.0-5.4 eV. Electrical characterization was carried out on Al/ Gd 2 O 3 / Si metal-insulator-semiconductor structures by capacitance-voltage ͑C -V͒ and current-voltage analyses. The effective dielectric constant of the films was in the range of 7-23. The bidirectional C -V characteristics show a counterclockwise hysteresis due to the presence of slow interface traps. A minimum leakage current of 4.6ϫ 10 -5 A/cm 2 at the 1-MV/ cm field was demonstrated.

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