Showing papers in "Japanese Journal of Applied Physics in 1990"
TL;DR: In this paper, a correlation between the nanoscale B-site order and relaxor on glassy ferroelectric behavior is found in these lead perovskites, and a hypothesis is suggested which relates 0-3 polar connectivity to order-disorder connectivity.
Abstract: From transmission electron microscopy studies on several complex lead perovskite compounds Pb(B'B'')O3, and their solid solutions a classification can be obtained based on B-cation order. This classification divides the complex lead perovskites into three subgroups; random occupation or disordered, nanoscale or short coherent long-range order and long coherent long-range order of B-site cations. A correlation between the nanoscale B-site order and relaxor on glassy ferroelectric behavior is found in these lead perovskites. An hypothesis is suggested which relates 0-3 polar connectivity to 0-3 order-disorder connectivity. This hypothesis is discussed with relation to present theories [G. A. Smolenskii: J. Phys. Soc. Jpn. (1970) Suppl., p. 26, L. E. Cross: Ferroelectrics 76 (1987) 241, T. L. Renieke and K. L. Ngai: Solid State Commun. 18 (1973) 1543] and reported experimental results of the perovskite relaxor ferroelectrics.
319 citations
TL;DR: In this paper, the conoscopic figure in the antiferroelectric smectic CA* phase does not shift its center and is biaxial with its optic plane perpendicular to the field direction.
Abstract: Molecular orientational structures in MHPOBC were studied by means of conoscope observation. Contrary to a ferroelectric response of the conoscope to an electric field in the smectic C* phase, the conoscopic figure in the antiferroelectric smectic CA* phase does not shift its center and is biaxial with its optic plane perpendicular to the field direction. This conoscope change is only due to a dielectric contribution, indicating the existence of the inherent threshold in the electric field induced transition to the ferroelectric phase. In between the ferroelectric and antiferroelectric phases, a kind of ferrielectric phase was clearly distinguished in the field response of the conoscopic figure; the shift of the conoscope center perpendicular to the applied field and the biaxial optic plane parallel to the field suggest a novel molecular orientational structure.
216 citations
TL;DR: In this article, a new type of singularity is formed on Si wafer surface by the Standard Cleaning 1 (SC1) of the RCA cleaning process, which correspond to small shallow pits caused by the etching effect of the SC1 cleaning solution.
Abstract: It is clarified that a new type of singularity is formed on Si wafer surface by the Standard Cleaning 1 (SC1) of the RCA cleaning process. Such singularities are perceived by laser particle counters as small particles on wafers. It is shown that the singularities correspond to small shallow pits caused by the etching effect of the SC1 cleaning solution. The origin of the pits is presumed to be some kind of defect in the melt-grown crystals.
206 citations
TL;DR: In this article, the authors have prepared polyacetylene (ν-(CH)x) yielding a conductivity of more than 105 S/cm, by making some modifications on Naarmann et al.'s method, which may suggest the formation of a staging structure and/or the transformation to metallic phase.
Abstract: We have prepared polyacetylene (ν-(CH)x) yielding a conductivity of more than 105 S/cm, by making some modifications on Naarmann et al.'s method. Structural analyses of this polymer were carried out by use of various analysis techniques such as SEM, IR and resonance Raman spectroscopy to characterize ν-(CH)x. No distinct differences in structure between conventional polyacetylene and ν-(CH)x were observed except for morphology and specific gravity. Upon iodine doping, conductivity increases stepwisely, which may suggest the formation of a staging structure and/or the transformation to metallic phase. However, in the temperature dependence of conductivity, we could not find any differences which distinguish the metallic ν-(CH)x from conventional polyacetylene.
204 citations
TL;DR: In this paper, the role of the dimensional effect in both piezoelectricity and electrostriction was discussed and a linear relationship between x and D was shown to be proportional to D2.
Abstract: Electric-field-induced changes in thickness have been measured interferometrically for thin films of ferroelectric VDF/TrFE copolymers. For sinusoidal fields high enough to induce ferroelectric switching, the strain x in the thickness direction draws a hysteresis loop of butterfly shape while the electric displacement D draws a conventional square D–E hysteresis loop. The x is shown to be proportional to D2. Their ratio gives the electrostriction constant κ33 ranging from -2.1 to -2.5 m4/C2. Low-field measurements for poled samples with remnant polarization Pr yield a linear relationship between x and D. The piezoelectric constant given by the ratio x/D coincides with 2κ33Pr, implying that the piezoelectric activity of VDF copolymers originates from electrostrictive coupling as does that of traditional ferroelectrics. The role of the dimensional effect in both piezoelectricity and electrostriction is discussed.
197 citations
TL;DR: Bi2Sr2Ca1Cu2Ox textured tapes with an excellent Jc were synthesized by doctor-blade casting and a melt process as mentioned in this paper, where green tape was laid on a silver foil and oxide/silver composite tape was heat treated.
Abstract: Bi2Sr2Ca1Cu2Ox textured tapes with an excellent Jc were synthesized by doctor-blade casting and a melt process Green tape was laid on a silver foil and oxide/silver composite tape was heat treated A highly textured microstructure was formed by slow cooling from 890°C to 870°C with the oxide in a partially melted state The highest Tc and Jc (77 K, 0 T), 89 K and 13×104 A/cm2, respectively, were obtained by quenching from 870°C However, Jc at 42 K was higher for the sample slowly cooled to room temperature and reached 14×105 A/cm2 at 25 T These results indicate the potential for the practical application of Bi-based oxide superconductors at both 77 K and 42 K
177 citations
TL;DR: In this paper, the first observation of the room temperature stimulated emission near UV from a GaN film which was grown by metalorganic vapor phase epitaxy on a (0001) sapphire substrate using an AlN buffer layer was reported.
Abstract: We report the first observation of the room temperature stimulated emission near UV from a GaN film which was grown by metalorganic vapor phase epitaxy on a (0001) sapphire substrate using an AlN buffer layer This indicates that the GaN film is promising for the realization of an UV laser diode
170 citations
TL;DR: In this article, a copper nitride thin film was prepared by using the ion-assisted deposition in which accelerated nitrogen ions were irradiated during the deposition of copper metal, and the degree of nitrification of the film was controlled by changing the ion current density.
Abstract: Copper nitride thin films were prepared by using the ion-assisted deposition in which accelerated nitrogen ions were irradiated during the deposition of copper metal. The degree of nitrification of the film was controlled by changing the ion current density. The reflection coefficient of the prepared copper nitride films decreased with the increase of the ion current density. The reflection coefficient was about 30% at 780 nm wavelength, and it recovered to 70% after the film was heated at 300°C. The preliminary experiment of write-once optical recording of this film was carried out, and the viability of its practical use in new media was confirmed.
168 citations
TL;DR: An extremely large levitation force of as high as 30 N at a height of 1 mm was achieved in Ag-doped YBaCuO fabricated by the Melt-Powder-Melt-Growth process using a repulsive force against a 0.4 T rare-earth magnet at 77 K as discussed by the authors.
Abstract: An extremely large levitation force of as high as 30 N at a height of 1 mm was achieved in Ag-doped YBaCuO fabricated by the Melt-Powder-Melt-Growth process using a repulsive force against a 0.4 T rare-earth magnet at 77 K. The combination of a large Jc value and large shielding current loop is the source of such a large levitation force.
163 citations
TL;DR: In this paper, the authors investigated the silicidation process of the Ni/a-Si:H system on a fused silica substrate mainly by in situ electric resistance measurement.
Abstract: We have investigated the silicidation process of the Ni/a-Si:H system on a fused silica substrate mainly by in situ electric resistance measurement. A rise of the resistance is observed in the temperature range of 480–510°C of the resistance curve at a heating rate of 2 K/min. The results of the RBS measurements and the XRD measurements show that the rise of the resistance originates from the diffusion of Ni from the NiSi2 layer to a-Si:H film, and that the a-Si:H crystallizes during the diffusion. Noting that the crystallization temperature of a-Si:H film is higher than 700°C, the present crystallization occurs at a much lower temperature. It is suggested that this low-temperature crystallization is induced by heterogeneous nucleation, where the NiSi2 becomes the nucleus for Si crystallization.
158 citations
TL;DR: In this article, a sintered CeO2 target was ablated by ArF excimer laser to deposit films on Si(001), (111) and (110) substrates at temperatures ranging from 600 to 700°C.
Abstract: In a newly developed ultrahigh-vacuum (UHV) film preparation system equipped with in situ reflection high-energy electron diffraction (RHEED) and X-ray photoelectron spectrometer (XPS) analyzer, a sintered CeO2 target was ablated by ArF excimer laser to deposit films on Si(001), (111) and (110) substrates at temperatures ranging from 600 to 700°C. Tetravalence of the Ce in the films was confirmed by XPS, indicating that stoichiometric CeO2 was formed even in the UHV (≤10-6 Torr) condition. The orientation of deposited CeO2 films was strongly dependent on the surface state of Si substrates. The results are well explained in terms of preferential arrangement of the first plane of growing CeO2 by its interaction with substrate surface.
TL;DR: In this article, a block layer is proposed to isolate each CuO2-sheet and control carrier density within the Cu-O plane, which can isolate each sheet and control the carrier density.
Abstract: Structures of layered copper oxide compounds and relating high-temperature superconductors are classified by using the concept of the block layer which can isolate each CuO2-sheet and control carrier density within the Cu-O plane. Particular emphasis is laid on the Cu-O network dependent physico-chemical properties which are entirely governed by ordering and combination of constituent block layers. By the new classification method, structures and carrier-doping characteristics are predicted for prospective but hitherto unknown CuO2-layered superconductors. Possible importance of the concept of the block layer is pointed out in epitaxial growth of superconducting structures.
TL;DR: The role played by oxygen impurities in the optical activation of the 1.54 µm luminescence was demonstrated by implanting oxygen into Er implanted layers in silicon at concentrations comparable to those of Er.
Abstract: Luminescence spectra and SIMS measurements of Er-doped silicon are presented in this paper. Luminescence was found to be stronger in Czochralski-grown Si crystals, known to contain up to 1018 cm-3 of oxygen center. Direct role played by oxygen impurities in the optical activation of the 1.54 µm luminescence was demonstrated by implanting oxygen into Er implanted layers in silicon at concentrations comparable to those of Er. Possible mechanisms of enhancement of photoluminescence are discussed.
TL;DR: Ferroelectric PZT thin films were prepared by the simultaneous deposition of PbO, ZrO2 and TiO2 on heated substrates under a reduced pressure of 6 Torr as mentioned in this paper.
Abstract: Ferroelectric PZT thin films were prepared by the simultaneous deposition of PbO, ZrO2 and TiO2 on heated substrates under a reduced pressure of 6 Torr. Both tetraethyl lead-zirconium tetraisopropoxide and tetradipivaloylmethane-titanium tetraisopropoxide systems were examined as source materials. The films obtained at 500° to 650°C with those systems were constituted of PZT of the single perovskite phase, and highly c-axis-oriented films were grown on MgO(100) with the latter system. The c-axis orientation suggests an epitaxial growth of PZT on the substrates. With increasing molar fraction of ZrO2 in the PZT, the crystals were transformed from a tetragonal to rhom-bohedral structure. The film deposition rates were 100 to 1000 A/min, i.e., more than ten times those obtained by the conventional sputtering method.
TL;DR: In this article, Boron-doped homo-epitaxial films were deposited by microwave plasma CVD on synthesized single-crystal diamonds, and the effect of the surface orientation of substrates was found in the conductivity of highly doped films.
Abstract: Boron-doped homo-epitaxial films were deposited by microwave plasma CVD on synthesized single-crystal diamonds. Boron concentration in the films was determined by the boron concentration in the reactant gases. The crystallinity of boron- doped films was found to be affected by the boron concentration in the reactant gases. The conductivity of boron doped films was determined by the concentration of boron, and the activation energy was nearly the same as for natural IIb diamonds. The effect of the surface orientation of substrates was found in the conductivity of highly doped films. The result of the Hall effect measurement indicated that the mobility of boron-doped diamond epitaxial films was 70 cm2/Vs even at 500°C.
TL;DR: In this article, the spatial distribution of SiH3 radicals between the electrodes was measured to obtain the incident flux density of siH3 to the electrode surface and the growth rate of a-Si:H was also measured in the same plasma.
Abstract: Infrared diode laser absorption spectroscopy (IRLAS) was applied to the measurement of SiH3 in a RF silane P-CVD chamber with parallel plate electrodes. The spatial distribution of SiH3 radicals between the electrodes was measured to obtain the incident flux density of SiH3 to the electrode surface. The growth rate of a-Si:H was also measured in the same plasma. These data were used to estimate the contribution of SiH3 to a-Si:H thin-film growth.
TL;DR: In this article, a tetragonal "1-2-3" type was synthesized as a superconductor with an onset temperature of 60 K, where a and c are 3.7949 and 11.4102 A, respectively.
Abstract: At a high oxygen pressure of 7 GPa and high temperature of 1380°C, YSr2Cu3Oy was synthesized as a single phase. The crystal structure is a tetragonal "1-2-3" type, where a and c are 3.7949 A and 11.4102 A, respectively. This material is a superconductor with an onset temperature of 60 K.
TL;DR: In this article, a number of important parameters, such as gain, modulation response and threshold current in modulation-doped multi-quantum-well (MD-MQW) lasers are theoretically investigated.
Abstract: A number of important parameters, such as gain, modulation response and threshold current in modulation-doped multi-quantum-well (MD-MQW) lasers are theoretically investigated. The analytical results indicate that the relaxation oscillation frequency of p-type MD-MQW lasers is enhanced by a factor of 4 compared with DH lasers, and that the linewidth enhancement factor of p-type MD-MQW lasers is reduced to 1/4 that of undoped MQW lasers. The threshold current density of n-type MD-MQW lasers is reduced to 1/2~1/4 that of undoped MQW lasers. The improvements in these properties basically result from the unsatisfied charge neutrality due to the modulation doped effect and from asymmetry in density of states between conduction band and valence bands in III-V materials.
TL;DR: In this article, an explanation for the mechanism generating a pretilted nematic liquid crystal conformation aligned on rubbed alkylbranched polyimide layers is given based on a steric interaction model.
Abstract: An explanation for the mechanism generating a pretilted nematic liquid crystal conformation aligned on rubbed alkylbranched-polyimide layers is given based on a steric interaction model. An analytical calculation using this model was shown to agree fairly well with the data of torsional coupling strength obtained in this work.
TL;DR: By applying the Landau theory, the appearance of the antiferroelectric phase in smectic liquid crystals and the double hysteresis loop are interpreted Several types of phase sequences are obtained phenomenologically.
Abstract: By applying the Landau theory, the appearance of the antiferroelectric phase in smectic liquid crystals and the double hysteresis loop are interpreted Several types of phase sequences including the antiferroelectric, ferroelectric and/or ferrielectric phase are obtained phenomenologically The D-E curves in the antiferroelectric phase are classified into three types depending on temperature and the coefficients of the fourth-order terms in the free energy
TL;DR: In this paper, the sputtering of a hexagonal BN sintered target under a negative self-bias voltage applied to Si substrates and a sputtering gas composition of Ar/N2 was found to contain a c-BN phase.
Abstract: Cubic boron nitride (c-BN) films have been prepared by sputtering of a hexagonal BN sintered target under a negative self-bias voltage applied to Si substrates and a sputtering gas composition of Ar/N2. A c-BN phase was found to be contained only in the films prepared in pure Ar discharge with a negative self-bias above a threshold value. Moreover, the ratio of c-BN to hexagonal boron nitride increased with increasing negative self-bias voltage. The films consisting mainly of the c-BN phase were easily peeled from Si substrates on exposure to air because of their strong compressive stress.
TL;DR: In this paper, the existence of a subphase, SmCα*, between SmA and the normal SmC* (SmCβ*) was confirmed by means of dielectric measurements.
Abstract: In the phase transition from the paraelectric smectic A to the antiferroelectric SmCA* phase via the ferroelectric SmC* phase in MHPOBC, the existence of a subphase, SmCα*, between SmA and the normal SmC* (SmCβ*) was confirmed in addition to that of another subphase, SmCγ*, between SmC* and SmCA* by means of dielectric measurements. It was also confirmed that these subphases, SmCα* and SmCγ*, disappear in the same compound of lower optical purity as observed by DSC. The model structure of the SmCα* phase is speculated on the basis of the dielectric measurements.
TL;DR: In this paper, high-quality diamond epitaxial films were obtained on Ib diamond (100) substrates by means of the microwave plasma-assisted chemical-vapor-deposition (CVD) method.
Abstract: High-quality diamond epitaxial films were obtained on Ib diamond (100) substrates by means of the microwave plasma-assisted chemical-vapor-deposition (CVD) method. For the source gas, CH4 and H2 gases were used in different CH4 concentrations (CH4/H2), from 1 vol% to 8 vol%. At CH4/H2=6%, the surfaces of the films were smooth and streaks were observed by reflection high-energy electron diffraction (RHEED). Raman spectra showed that they had no graphitic components. In contrast, Raman spectra showed that both the (110) epitaxial films and the polycrystalline films grown at CH4=6% had graphitic components.
TL;DR: In this article, a realistic model structure of the ferrielectric phase was proposed by taking into account the apparent tilt angle measurements, and the electric and optical responses were investigated in both the antiferroelectric and the ferrilectric phases of MHPOBC under triangular waves of various frequencies.
Abstract: A realistic model structure of the ferrielectric phase is proposed by taking into account the apparent tilt angle measurements. On the basis of the model, the electric and optical responses are investigated in the ferrielectric SmCγ* as well as in the antiferroelectric SmCA* phases of MHPOBC (C8H17O---COO--COOC*H(CH3)C6H13) under triangular waves of various frequencies. At low frequencies, D-E curves show double and triple hysteresis loops characteristic of the antiferroelectric and the ferrielectric phases, respectively. T (transmittance)-E curves also reveal similar hysteresis loops. With increasing frequency, the direct switching between the two ferroelectric states occurs without passing through the antiferroelectric state or the ferrielectric states. The complicated frequency dependence is interpreted based on the spatially inhomogeneous domain switching.
TL;DR: In this paper, the authors analyzed the behavior of a quartz crystal microbalance (QCM) in the experimental environments of air and liquid using a Mason equivalent circuit and found that the mass loading effect of QCM could be regarded as an inductance increase, and the analytical equation of the frequency shift was derived.
Abstract: The authors analyzed the behavior of a quartz crystal microbalance (QCM) in the experimental environments of air and liquid using a Mason equivalent circuit. It was found that the mass loading effect of QCM could be regarded as an inductance increase, and the analytical equation of the frequency shift, which is valid over the wide range of the thickness of a loading film, was derived. Utilizing this equation, the frequency shift can be predicted without solving the transcendental equation. Furthermore, it was found that various kinds of QCM problems, such as liquid loading and mass loading in liquid, could be solved using the same method because the acoustic load was expressed as a circuit component. Finally, the method to enhance mass loading sensitivity by depositing a thick film with low acoustic impedance over the quartz plate, was suggested.
TL;DR: In this article, the authors investigated the relationship between the open-circuit voltage of hydrogenated amorphous silicon (a-Si:H) p-i-n solar cells and the surface morphology of transparent electrodes and the i-layer thickness.
Abstract: The open-circuit voltage of hydrogenated amorphous silicon (a-Si:H) p-i-n solar cells depends on the surface morphology of transparent electrodes and the i-layer thickness. We have studied the relationship between the Voc and these parameters experimentally. To investigate the detailed mechanism of the Voc drop, transmission and scanning electron microscopies (TEM and SEM) were used, and it was found by the TEM images that white stripelike defective regions were generated in the i-layer deposited on highly textured transparent electrodes. From the current-voltage characteristics of these solar cells under the dark condition, the relationship between the defects and the electrical properties of the cells has been studied. The results showed that the defect acts as a recombination center of carriers.
TL;DR: In this article, a wide-aperture color projection principle is presented whose functional parts, namely, polarizers, bandpass filters and electrooptical modulators, consist entirely of liquid crystal elements.
Abstract: A wide-aperture, color projection principle is presented whose functional parts, namely, polarizers, bandpass filters and electrooptical modulators, consist entirely of liquid crystal elements. The concept ideally enables one hundred percent input-output light conversion. The angular and wavelength dependences of planar cholesteric layers and layer combinations are shown. From them optical filter/polarizer elements result with adjustable center wavelengths and tunable bandwidths. The filters comprise novel cholesteric liquid crystals with a temperature dependence of their center wavelengths as low as 0.06 nm/°C. New, circularly polarized operating modes for twisted nematic (TN-LCDs) and other field effects exhibit not only low threshold voltages, but also voltage-transmission (reflection) characteristics whose slope is adjustable over a wide range. Thus, the new modes are applicable in high-information-content, actively addressed television TN-LCDs requiring gray scale, as well as in displays requiring large time multiplexing rates approaching those of supertwist LCDs.
TL;DR: In this paper, a novel method of nitridation of thin SiO2 film (30 C/cm2) was proposed, which indicates a quite uniform interface ordered within at least one or two atomic layers.
Abstract: A novel method of nitridation of thin SiO2 film ( 30 C/cm2) and indicates a quite uniform interface ordered within at least one or two atomic layers.
TL;DR: In this paper, step band regions of the DC-heating-induced bunching surface break up into finer step bands (subbands) and (111) facets below the (7×7)↔(1×1) phase transition temperature (Tc=830°C).
Abstract: Step bunching on a 1°-misoriented Si (111) surface induced by DC resistive heating is observed by ultrahigh-vacuum scanning electron microscopy. Step band regions of the DC-heating-induced bunching surface break up into finer step bands (subbands) and (111) facets below the (7×7)↔(1×1) phase transition temperature (Tc=830°C). The temperature dependence of bunching-inducing current direction on the vicinal surface is the same as that of nearly flat (111) surfaces previously reported, except that bunching is induced for the opposite current direction to nearly flat (111) surfaces below Tc.
TL;DR: In this article, an organic ion-complex crystal composed of protonated merocyanine and p-toluenesulfonate anion was synthesized for second-order nonlinear optics.
Abstract: The novel organic ion-complex crystal composed of protonated merocyanine and p-toluenesulfonate anion, i.e., 1-methyl-4-(2-(4-hydroxyphenyl)vinyl)pyridinium 4-toluenesulfonate (MC-PTS), was synthesized for second-order nonlinear optics. Crystal structure analysis revealed that MC-PTS crystallized in the space group of P1, i.e., the most desired space group for waveguide applications where molecular dipoles are perfectly aligned in one direction. It was also pointed out that the tetrahedral sulfonate anion plays the role of a chiral handle to give noncentrosymmetric space groups.