[en] Electrostatic charge properties on polypropylene film have been characterized by atomic force microscopy and electrostatic force microscopy. The measurements have been carried out after the polypropylene film was electrified by contact and separation process in an atmosphere of controlled humidity. The negative and positive charge in concave surface has been observed. The correlation between concave surface and charge position suggests that the electrostatic charges could be caused by localized contact. On the other hand, positive charge on a flat surface has been observed. The absence of a relationship between surface profile and charge position suggests that the electrostatic charge should be caused by discharge during the separation process. The spatial migration of other positive charges through surface roughness has been observed. The results suggest that there could be some electron traps on the surface roughness and some potentials on the polypropylene film.

[en] A percolated-induced ferromagnetic moment in KNi_xZn_1-xF³ for x = 0:57, which is Heisenberg-type diluted three-dimensional magnet, is studied by electron spin resonance. Below T_C ' 24 K, ferrimagnetic resonance spectra appeared as expected. On the other hand, in KCo_xZn_1-xF³ for 0.49 ≥ x < 1, which are Ising-type diluted three-dimensional magnets, a percolated-induced ferromagnetic moment did not appear. This difference may play an important key role in Coulomb repulsion between Zn²⁺ ions because KNi_xZn_1-xF³ consists of simple cubic lattice, on the other hand tetragonal distortion exists in KCo_xZn_1-xF³.

[en] Flat surface is essential to base electrodes of sandwich type Josephson junctions. In the present study, c-axis YBa₂Cu₃O₇ (c-YBCO) films with excellent surface smoothness were fabricated by off-axis sputtering. For the flat surfaces, key parameters in the sputtering process were growth temperature, atmosphere conditions and surface nature of substrates. The correlation between the sputtering conditions and the characteristic of the c-YBCO films reveal the following phenomena; i) The films deposited at low temperature of 660 deg. C showed a low zero-resistance temperature because of a poor connection between the c-axis crystallites. Surfaces of these low temperature grown films involve large and rectangular shaped a-axis grains, thereby the peak-to-valley (PV) amplitude of the surface was beyond 80 nm. The experiments indicate that the growth of the grains should be caused by low surface diffusion of adatoms at the low growth temperature. ii) Contrarily, at high T_s above 770 deg. C, a serious deviation of film composition from the stoichiometry took places, which also promoted an outgrowth of a-axis grains. Consequently, the high temperature grown films had seriously rough surfaces (PV amplitude > 25 nm). iii) The growth at the optimised T_s of 765 deg. C led a remarkable reduction of surface roughness (root-mean-square (RMS) of the roughness < 1.8 nm) without any degradation of superconducting properties. The achieved surface morphology is classified as one of the smoothest surfaces of the YBCO film grow by sputtering. iv) A density of the a-axis outgrowth was related to the surface defects of the substrate. The usage of SrTiO₃ (100) plane consists of atomically flat and wide terraces and unit-cell high steps resulted in almost outgrowth-face surface with an excellent smoothness (PV amplitude < 10 nm, RMS of the roughness < 1.0 nm)

[en] (Cu, C)-1201 films have been grown on SrCuO₂ buffer layer over SrTiO₃ (100) by pulse laser deposition. Effects of the insertion of SrCuO₂ buffer on growth mode of the 1201 phase has been investigated by comparing in-situ RHEED pattern of the films growth on SrCuO₂ / SrTiO₃, SrTiO₃ and NdGaO₃. (Cu, Q-1201 films directly grown on SrTiO₃ and NdGaO₃ exhibit diffusive streak patterns in the beginning of the film growth. On the other hand, the films on the buffer show sharp streaks in the beginning from the film growth on buffer, a-axis parameters of the films on SrTiO₃ and NdGaO₃ estimated by RHEED patterns drastically expanded from 3.90 ± 0.06 A and 3.93 ± 0.10 A at 10 nm thick to 4.07 ± 0.05 A and 3.99 ± 0.03 A at 40 nm thick, respectively. The films on 10 nm thick buffer gradually expanded from 3.95 ± 0.05 A at 10 nm thick to 4.01 ± 0.05 A at 40 nm thick. The films on 10 nm and 20 nm thick buffer layers showed the rises of superconducting onset temperature T_c-onset to 72 K and 62 K, respectively, whereas T_c-onset of the films directly grown on SrTiO₃ was about 50 K. Due to the growth mode without misfit dislocations in the beginning of the film growth, the SrCuO₂ buffer could strain the 1201 phase. These results indicated that the interfacial strain should be important T_c for (Cu, Q-1201 films, and superlattice based on it.

[en] Transport properties of (Cu, C)Ba₂CuO_x [(Cu, C)-1201] thin films have been characterized by in situ temperature dependence of resistivity, without breaking vacuum from the deposition to the measurement. In in situ transport properties measurements, the obtained results reveal that (Cu, C)Ba₂CuO_x films exhibit T_c > 20 K on the cased of conductivity at 290 K (σ_[290K]) > 4 x 10² S/cm and temperature coefficient of resistivity (TCR) > 1.5 x 10^-3 K^-1, and doping level of them should be in between under-doped and optimally-doped states. Their results suggest that there would be possible to further increases of T_c, and XPS data suggest that (Cu, C)-system should have the excellent dopability in their charge reservoir and the possibility of low anisotropy.

[en] (Cu, C)-Ba-O thin films have been deposited at low growth temperature of 450-570 ^oC by pulsed laser deposition method. A control of CO₂ gas pressure and the growth temperature, usage of BaCu_yO_x pellet target resulted in an expansion of twice c-axis length of BaCuO₂ structure (2c phase) and a significant rise of conductivity. Measurements of in-situ XPS suggest that the 2c phase should be (Cu, C)Ba₂CuO_x [(Cu, C)-1201]. The maximum temperature of onset of the superconducting transition and zero resistance state obtained so far were 60 and 47 K, respectively.

[en] Transport properties of (Cu, C)-1201 thin films have been characterized by in-situ four probe method without breaking vacuum, subsequent to their growth by pulsed laser deposition, in order to clarify intrinsic transport properties. Owing to the in-situ measurements, degradation of contact resistance and normal state conductivity were successfully suppressed. Obtained results reveal the positive correlation between T_c and normal state conductivity δ at 290 K, and that between T_c and temperature coefficient of resistivity (TCR) at 290 K. The films exhibit T_c(ρ=0) > 20 K on the cases of δ_[290K] > 4 x 10² S/cm and TCR > 1.5 x 10^-3 K^-1. The high T_c with low conductivity of (Cu, C)-1201 films indicates the presence of extrinsic defects such as grain boundaries. The absence of saturation of T_c with an increase of TCR indicates doping level of the (Cu, C)-1201 films in this study should be in between under-doped to optimally-doped states. They suggest there would be some room for further increases of T_c.

[en] Ba-Cu-O films have been grown by pulsed laser deposition. Investigation of their transport properties and characterization of electronic structure by in-situ photoemission spectroscopy have been carried out. The films grown at 450 ∼ 480 deg. C from BaCuO₂ target had simple infinite layer structure with lattice parameter of a and c about 0.385 and 0.405 nm, respectively. Conductivity of these films were, however, poor. Usage of BaCu_0.75O_x target and addition of CO₂ into the growth atmosphere resulted in an expansion of c-axis length up to 0.810 ∼ 0.835 nm and a significant rise of conductivity. This structure is represented as '2c'. For the 2c phase, conductivity above of 10³ S/cm was achieved by adjusting their growth temperature in the range of 500 ∼ 530 deg. C. Most of the highly conductive 2c phase showed superconductivity. The maximum temperature of onset of the superconducting transition and zero resistance state obtained so far were 60 and 47 K, respectively. Finite spectral weights at Fermi level were successfully observed in in-situ photoemission spectra of the 2c phase. In valence band region, a prominent peak with u 3d character located at a binding energy around 1.6 eV. Though this low binding energy suggested a rather high hole concentration of mobile holes were around middle of 10²¹ cm^-3 range. These results about electronic structure indicate a coexistence of conventional CuO₂ planes and distorted ones. The latter structure might play charge-reserving blocks, though some portions of holes should localize in them. Correlations between the properties and electronic structure are to be discussed

[en] Change of electronic structure of superconducting (Cu, C)-1201 thin films grown by pulsed laser deposition with superconducting critical temperature T_c has been characterized by means of in situ photoemission spectroscopy. The finite spectral weight at the Fermi level in the valence band of (Cu, C)-1201 superconducting thin films and a rigid-band-like approach of the main peak of the valence band toward the Fermi level with a rise of T_c has been observed, which reveals hole-doping-induced superconductivity of this system. The obtained Ba 4d and Cu 2p signals with an increase of T_c suggest excess oxygen should be introduced around Ba ions in the early stage of the emergence of superconductivity. Then, they should be preferentially introduced around Cu ions. The changes of core signals with T_c and comparisons of the obtained data with infinite-layer and other cuprate superconductor compounds suggest that the (Cu, C)-O charge reservoir in this system is in the heavily hole-doped state, similar to that of the Cu-O chain in YBa₂Cu₃O_7-δ