[en] We have studied the origin of the cooperative Jahn-Teller effect and the metamagnetic transition in the orthorhombic compound PrCu₂. We have determined the anisotropic ferroquadrupole phase diagram by measuring the specific heat and thermal expansion under magnetic fields. With increasing the field, the Jahn-Teller transition temperature increases slightly for the field along a- and c-axes, while it decreases intensively along the b-axis. The phase diagram can be explained quantitatively by including the quadrupolar interaction of -K_JT< O_xy>O_xy in the crystalline electric field and Zeeman Hamiltonian. The metamagnetic transition, which brings about the conversion between the easy (a)- and hard (c)-axes magnetization, has been also studied through the magnetostriction. This phenomenon is also explained quantitatively on the basis of the quadrupolar interaction of -K_M< O₂²>O₂². The sign of < O₂²> is found to be negative in the state where the c-axis is the hard one, while it changes from negative to positive above the metamagnetic transition field. (author)

[en] In the present work the microstructure of anatase TiO₂ film deposited on LaAlO₃ and SrTiO₃ substrates by pulse laser ablation was investigated using high-resolution transmission electron microscopy (HRTEM) and electron diffraction analysis. The experimental observations reveal the structural features of the interface between the film and the substrate and three main types of crystal defects in the anatase TiO₂ film. Observation of the interface showed that the anatase was epitaxially grown on the substrates although defects, such as dislocations and distorted regions can be observed near the interface. Using HRTEM observation several types of defects were found in the deposited film. These defects include both dislocations with the (112) and (001) planes as extra atom planes and micro-twins with the (112) plane as the twin plane

[en] Binary alloy Schottky contacts on ZnO are developed using the combinatorial ion beam deposition system. The compositional fraction of the Schottky binary alloy was continuously changed by the composition spread technique. Pt-Ru alloy composition spreads were deposited as the Schottky metal alloys. It was shown that the compositional fraction of the Schottky binary alloys changed continuously. A Pt-Ru alloy metal film was grown on o-polar ZnO epitaxially, and its crystal structures changed from the Pt-phase (cubic structure) to the Ru-phase (hexagonal structure) in the Pt-Ru alloy phase diagram. Schottky barrier heights determined by current-voltage measurements increased with increasing Pt content. By combining the ion beam deposition and combinatorial system, the Schottky barrier heights of the Schottky binary alloys have been controlled systematically. (author)

[en] A ternary alloyed thin film library of HfO₂-Y₂O₃-Al₂O₃ was grown on a Si(1 0 0) substrate in a few hours by a new pulsed laser deposition (PLD) system installed with a masking and substrate rotating scheme. This specially designed combinatorial ternary composition spread method enabled us to fabricate continuous ternary and binary composition spread film libraries. It is noteworthy that the library made by this system is addressable; each film composition covers the full range (from 0 to 100%) and can be directly correlated with the film location in the ternary and binary phase diagram. Rapid permittivity measurement on the film libraries was carried out by a scanning microwave microscope, while the crystal structure was by a combinatorial X-ray diffractometer (XRD). The (HfO₂)₆(Y₂O₃)₁(Al₂O₃)₃ ternary composition area in an amorphous phase was found to have a dielectric constant higher than HfO₂-Y₂O₃ binary area. This ternary oxide is promising as amorphous gate dielectric material

[en] We have studied the metamagnetism in PrCu₂ via the magnetostriction. The metamagnetic transition accompanies a conversion between an easy and a hard axes in magnetization and also a huge magnetostriction. It is due to the magnetoelastic effect arising from the quadrupolar interaction, bringing about the rotation of the quadrupole moment. (orig.)

[en] We have studied the origin of the cooperative Jahn-Teller effect in PrCu₂. We have determined the anisotropic phase diagram by measuring the thermal expansion and the magnetostriction in magnetic fields up to 15 T. The Jahn-Teller transition temperature is almost constant for the field along the a- and c-axis, while it decreases with increasing the field along the b-axis. The phase diagram can be explained qualitatively by including the quadrupolar interaction for left angle O_xy right angle in the crystalline electric field Hamiltonian. (orig.)

[en] We have carefully reinvestigated the superconducting heavy-electron system CeCu₂Si₂ by preparing very homogeneous polycrystalline samples at many different compositions in the homogeneity range by levitation melting and discovered in the Cu-deficient region a weakly ferromagnetic phase, presumably due to heavy quasiparticles of the Kondo compound. We, in addition, confirmed that the superconducting phase emerges at the fading end of the novel ferromagnetic phase in a very limited region of the phase diagram, which has revealed some salient superconducting properties. (author). Letter-to-the-editor

[en] We report on ZF and TF-studies of PrCu₂ above the induced Jahn-Teller transition at 7.3 K. Generally a two-component signal is found, one showing inhomogeneous the other one homogeneous, temperature dependent line broadening. In ZF the former component is well represented by a Gaussian Kubo-Toyabe function with Δ ≅ 6.5 μs^-1 at 7.5 K, corresponding to a field width of 76 G. This is about 30 times larger than what is calculated to arise from the ¹⁴¹Pr-nuclear dipole moments alone, pointing to strong hyperfine enhanced features. TF-field scans at 12 K revealed that the enhancement is suppressed in external fields exceeding 1 kG. In parallel the Knight shift drops from very large values well above 10% at 100 G to shifts of the order of 1% above 1 kG. A scaling of the Knight shifts with the corresponding relaxation rates seems to imply that the strange field dependence below 1 kG is associated with the magnetic susceptibility of the muons's nearest neighbour Pr³⁺-ions, a result for which we have no explanation yet to offer

[en] Gallium nitride (GaN) nanostructures were fabricated by focused-ion-beam-assisted chemical vapor deposition. Gallium precursor gas and atomic nitrogen radicals were irradiated onto the surface simultaneously during the irradiation of a Ga ion beam of 25 keV at 600 deg. C. Scanning electron microscopy observations revealed three-dimensional structures formed periodically on the substrates. Although near-band-edge emission from GaN was observed using this method, other luminescence attributed to defects and/or impurities was also observed. Surface damage caused by the ion beam was also observed. To improve the structural shape and optical properties, a two-step growth method is proposed. First, structure formation was performed at 300 deg. C. Second, nitridation was performed at 600 deg. C to make the GaN nanostructures stoichiometric and to activate the nitrogen in the structures. GaN nanostructures of a 200 nmx100 nm block of height 50 nm were fabricated and strong near-band-edge emission at 3.37 eV from GaN was observed

[en] Radio-frequency (rf) performances of a sub-100 nm MOSFET with two different gate dielectrics have been characterized. A 59 nm gate-length field-effect transistor (FET) with a SiON gate dielectric exhibited a cut-off frequency (f_T) and a maximum oscillation frequency (f_max) of 178 and 127 GHz, respectively. However, an FET with a HfSiON gate dielectric exhibited 148 and 122 GHz, respectively. The reduction in f_T has been found to be attributed to the degradation in the mobility and not to the dielectric relaxation of the HfSiON film. It has been confirmed that the high dielectric constant of HfSiON films can be utilized for future rf CMOS circuits at least up to 40 GHz