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A study was performed on the electronic structures and properties of perovskite compounds with the chemical formula ABX3and the monovalent copper ion (Cu+) as the A-site cation. Most Cu+-based perovskite chlorides (CuMCl3, where M denotes an element) had lower total energies than cesium (Cs)-based perovskite crystals. The energy gaps of CuMCl3perovskites with B-site cations spanning chromium (Cr) to zinc (Zn) were close to the ideal value for photovoltaic materials. The calculated carrier effective mass ratios indicated that CuMCl3should have a similar or higher carrier mobility than CsPbCl3(Pb=lead). Unlike Cs-based perovskites, the electron orbitals of Cu and the MCl6octahedron overlap, suggesting that the Cu+at the A-site should affect the stability of the crystal structure and the carrier mobility. The Cu+ion can be used as the A-site cation in ABX3perovskites to tune the composition of all-inorganic perovskite crystals and thereby increase the diversity of physical properties.

Graphical Abstract:

Carbon (C)/copper (Cu)-based materials with high thermal conductivity and good stability at high temperatures were developed by adding a small amount of zirconium, which has a low enthalpy of alloy formation with C and Cu. The felt-type C/C composites, which were impregnated by Cu and zirconium, provided 1.4 times higher thermal conductivity at 1300?K than that of the original carbon materials. Microstructural analysis showed that the increase of thermal conductivity is due to the formation of zirconium compounds at the C/Cu interface. These carbon-based materials could be one of the candidate materials for the plasma-facing components of the fusion devices.

Carbon (C)/copper (Cu)-based materials with high thermal conductivity and good stability at high temperatures were developed by adding a small amount of zirconium, which has a low enthalpy of alloy formation with C and Cu. The felt-type C/C composites, which were impregnated by Cu and zirconium, provided 1.4 times higher thermal conductivity at 1300 K than that of the original carbon materials. Microstructural analysis showed that the increase of thermal conductivity is due to the formation of zirconium compounds at the C/Cu interface. These carbon-based materials could be one of the candidate materials for the plasma-facing components of the fusion devices.

A monovalent copper ion (Cu+) with the same valence as formamidinium is focused on the present work, and the effects of A-site inorganic cations on the electronic structures and device performance are discussed from the experiments and the first-principles calculations. The addition of inorganic cations increased the conversion efficiencies, and the copper-doped device showed the highest conversion efficiency. In particular, the hysteresis of current density–voltage characteristics was significantly suppressed by the addition of Cu+, which would be due to suppression of iodine ion (I−) diffusion by electrostatic interaction between Cu+and I−. The addition of rubidium or cesium contributed to the increase in short-circuit current density by suppressing decomposition of perovskite crystals and formation of PbI2.

The crystal structures of various types of perovskite halide compounds were summarized and described. Atomic arrangements of these perovskite compounds can be investigated by X-ray diffraction and transmission electron microscopy. Based on the structural models of basic perovskite halides, X-ray and electron diffractions were calculated and discussed to compare with the experimental data. Other halides such as elemental substituted or cation ordered double perovskite compounds were also described. In addition to the ordinary 3-dimensional perovskites, low dimensional perovskites with 2-, 1-, or 0-dimensionalities were summarized. The structural stabilities of the perovskite halides could be investigated computing the tolerance and octahedral factors, which can be useful for the guideline of elemental substitution to improve the structures and properties, and several low toxic halides were proposed. For the device conformation, highly crystalline-orientated grains and dendritic structures can be formed and affected the photo-voltaic properties. The actual crystal structures of perovskite halides in the thin film configuration were studied by Rietveld analysis optimizing the atomic coordinates and occupancies with low residual factors. These results are useful for structure analysis of perovskite halide crystals, which are expected to be next-generation solar cell materials.

Transition metal doped cesium lead halide (CsPbI3) perovskite compounds were studied for application in photovoltaic solar cells. Electronic structures, chemical shifts of 207Pb and 127I-NMR, vibration modes in infrared and Raman spectra of transition metals (Mn2+, Fe2+or Cu2+)-doped CsPbI3perovskite compounds were studied by the first-principles calculation using density functional theory. The CsPb(Fe)I3perovskite crystals had a slight perturbation of crystal field in the coordination structure. The electron density distribution was delocalized on the 5porbital of I atom, the 3dorbital of Fe atom and the 6porbital of Pb atom. The first excited process was based on ligand metal charge transfer from the 5porbital on I atom to the 3dorbital of Fe atom. The chemical shifts of 127I-NMR were associated with the electron correlation of electron-nuclear spin interaction and nuclear quadrupole interactions based on electron field graduate. The asymmetric vibrations of Pb–I bonds stretching mode related to electron conductivity with scattering of the carrier diffusion as phonon effectiveness. The slight perturbation of the coordination structure in the CsPb(Fe)I3perovskite crystal will improve the photovoltaic and optical properties.

The stability of TiO2/CH3NH3PbI3–xClx-based photovoltaic devices in ambient air was evaluated upon adding PbI2and/or PbCl2. X-ray diffraction (XRD) peak intensities corresponding to the perovskite phase were increased by adding PbI2. After 7 weeks, the XRD peak intensities corresponding to the perovskite phase decreased and those corresponding to PbI2increased. The reaction rate constants for the decomposition of perovskite and formation of PbI2were estimated from these data. Thermodynamic calculations of the reaction between PbCl2and I2suggested that the formation of PbI2was not related to the added PbCl2but rather to excess PbI2. Open-circuit voltages and fill factors of the devices were improved with the 7 week time lapse because of the suppression of electron–hole recombination by the PbI2. In addition, the decomposition of perovskite grains was suppressed by the added PbI2. The I content of the perovskite phase decreased with the 7 week time lapse. However, the Cl content was largely constant after the 7 weeks, which suggested that Cl doping effectively stabilized the perovskite photovoltaic devices.

To avoid formation of the photo-inactive δ-phase of formamidinium-cesium lead triiodide, copper or germanium was added to the perovskite compounds to stabilize the photoactive α-phase. It was found that the substitution of lead by germanium (Ge) or copper (Cu) provided the stabilization of the α-phase in the present work. The first-principles molecular dynamics calculations indicated that displacements of formamidinium molecules were suppressed by the Ge doping. X-ray diffraction results indicated that the Ge or Cu doping of the perovskite compounds could be effective for suppression the phase transition from α- to δ-phase.

The additive effect of a gadolinium ion into a formamidinium lead iodide (FAPbI3) perovskite crystal on electronic structures and molecular dynamics was investigated for improving photovoltaic performance with stability. The electronic structures, band structure, partial density of state, and molecular dynamics were determined by first-principles calculation. The band distribution and charge transfer between the 5d orbital of the gadolinium atom, the 5p orbital of the iodine atom, and the 6p orbital of the lead atom promoted the carrier generation and diffusion related to short-circuit current density. The enthalpy and kinetic energy prompted stabilization of the gadolinium-doped crystal with a slight distortion of coordination structure, as compared with the decomposition of the FAPbI3crystal. Diffusion coefficients of iodine and lead ions in the FAPbI3crystal with defect were increased, predicting decomposition. The gadolinium-doped FAPbI3perovskite crystal has great potential for applications in photovoltaic devices by improving photovoltaic performance.

Experiments and first-principles calculations were performed to investigate the effects of Cu substitution in CH3NH3PbI3perovskite crystals. The first-principles calculations indicated that the energy level of the Cu d orbital formed above the VB maximum would be an acceptor or defect level. The effect of Cu addition on device properties was investigated, and the device with added 2% Cu provided higher efficiencies than the standard device. On the other hand, the decrease in short-circuit current density with increasing Cu content would be attributed to the defect level of the Cu d orbitals. First-principles calculations and experimental results provided insight into the function of Cu in CH3NH3-based perovskite crystals.

Conditions of nuclear fusion and nuclear fusion devices were described, and some possible applications of nanomaterials for nuclear fusion devices were presented in the present article. Muon-catalyzed fusion is one of methods for nuclear fusion to cause even at room temperature or lower, and protons or heavy ions with huge energy are irradiated to metals such as beryllium or copper, which results in emission of negative or positive charged muons from the metals. An experiment using a pyroelectric power source using lithium tantalite crystal was also reported to achieve nuclear fusion in a desktop-like device. Hydrogen storage is also important for the fusion devices, and the possibility of hydrogen storage in hydrogen storage metallic alloys was studied by diffusion calculation and potential calculation of deuterium fusion. Enhancement of deuterium diffusion in the Pd alloys would be one of the key points for energy materials. Carbon(C)/copper(Cu)-based composite materials with high thermal conductivity and good stability at high temperatures were also developed by adding a small amount of titanium, which has a low enthalpy of alloy formation with C and Cu. These carbon-based materials could be a candidate material for the plasma facing components of fusion devices.

TiO2/CH3NH3PbI3-xClx-based photovoltaic cells with a small amount of excess added PbI2were fabricated in ambient air. The fill factor and short-circuit current density were increased, which resulted in improvement of the photovoltaic performance. The recombination between a hole and an electron would be suppressed by the PbI2formation, and the external quantum efficiencies were increased.Excess PbI2addition to the perovskite CH3NH3PbI3(Cl) precursor solutions resulted in increase of the conversion efficiencies of the perovskite solar cells. The recombination between a hole and an electron would be suppressed by the PbI2formation, and the fill factor and short-circuit current density were increased.

CH3NH3PbI3perovskite solar cells using metal phthalocyanines (MPcs) with decaphenylcyclopentasilane (DPPS) are fabricated and characterized. The effect of addition of MPcs on the photovoltaic properties is investigated by changing the central element of the MPc and depositing MPc and DPPS successively on the perovskite layer. When silicon phthalocyanine is used to the cell, the microstructure of the perovskite film improves, which results in improvement of the open‐circuit voltage, fill factor, and photoconversion efficiency. For cells with only MPcs as the hole‐transport layer, the conversion efficiency increases by passivation with the phthalocyanine and crystal growth at room temperature. When silicon phthalocyanine is used to the cell, the microstructure of the perovskite film improves, which results in improvement of the open‐circuit voltage, fill factor, and photoconversion efficiency. For cells with only phthalocyanines as the hole‐transport layer, the conversion efficiency increases by passivation with the phthalocyanine and crystal growth at room temperature.

Electronic and crystal structures of CsPbIBr2perovskite compounds doped with copper (Cu) or tin (Sn) were investigated. From the band calculations, an energy gap of CsPbIBr2was reduced by the Cu or Sn doping, and optimized crystal structures of CsCuIBr2were compared with the fabricated crystals. Energy gaps of Cu- or Sn-doped CsPbIBr2were measured by optical absorption and external quantum efficiencies of the cells, and compared with the calculations. Addition of a small amount of Cu or Sn to the CsPbIBr2increased the short-circuit current density of the fabricated solar cells, which agree with the expected results from the calculated band structures and partial density of states.

Insoluble hierarchical polybithiophene/poly(ethylenedioxythiophene) thin films with a double-layered structure were prepared on an indium tin oxide transparent electrode by sequential electrochemical polymerization. The formation of the hierarchical structure was supported by the transmission absorption spectra and Raman scattering spectra of the double-layered polythiophene thin films. In the presence of residual oxygen as an electron acceptor, light irradiation on the polythiophene-modified electrodes generated stable cathodic photocurrents. A broad peak at approximately 440 nm corresponding to the absorption of neutral polythiophene was observed in the incident photon to current conversion efficiency profile of the polybithiophene/poly(ethylenedioxythiophene)-modified electrode. The photocurrent density of the polybithiophene/poly(ethylenedioxythiophene)-modified electrode was higher than that of the poly(ethylenedioxythiophene)-modified electrode.

[60]Fullerene assembly films consisting of C60and 1,2-diaminoethane (ethylenediamine) were easily fabricated on an amino-group-modified substrate by an alternate immersion process. The C60-assembly film was characterized after confirming the film formation using transmission absorption spectroscopy, transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. An inverted-type organic solar cell was fabricated by using the C60-assembly film as the acceptor layer in the photoactive layer of the solar cell. The resultant photoelectric conversion performances of the solar cells were evaluated using the photocurrent and photovoltage via the photoexcitation of polythiophene. The results suggested that the fabricated C60-assembly film works as an n-type semiconductor for polythiophene.

AbstractHigh-resolution electron microscopy and electron diffraction are quite useful for structural characterization of perovskite-type superconducting copper oxides on the atomic scale. Valuable information on the crystal structures and the microstructures could be obtained from observed high-resolution images if severe conditions such as thinner crystals and definite defocus values are satisfied. The structure images and electron diffraction patterns include information not only on accurate atomic coordinates of cations but also on ordered arrangements of oxygen atoms and oxygen vacancies. Crystal structures of the various perovskite-type copper oxides were analyzed from the observed structure images. Modulated structures, defects, intergowth, surfaces, and interfaces were also investigated.

Hierarchical polybithiophene/poly(3,4-ethylenedioxythiophene) films with polybithiophene layers of various thicknesses were prepared on an indium tin oxide glass transparent electrode by sequential electrochemical polymerization. In the presence of methyl viologen as a sacrificial electron acceptor, cathodic photocurrents were generated under monochromatic light irradiation. The irradiation light wavelength dependence of the incident photon-to-electron conversion efficiency changed drastically with the thickness of the polybithiophene layer. The main reason for the change in the photoelectric conversion properties was light absorption by the polybithiophene layer.

In this work we investigated the effects of the addition of guanidinium [C(NH2)3; GA] on CH3NH3PbI3perovskite solar cells fabricated at a high temperature of 190°C in atmospheric air. The addition of GA iodide and the insertion of decaphenylpentasilane between the perovskite and hole transport layer improved the external quantum efficiency and short-circuit current density, and the conversion efficiencies were stable after 1 month. X-ray diffraction showed that the lattice constant of the perovskite crystals was increased by the addition of GA, and addition of GA also improved the surface morphology. First-principles calculations on the density of states and band structures showed reduction of the total energy by the addition of GA and the effectiveness of the nitrogen atoms in GA.

Polysilane/fullerene bulk heterojunction solar cells were fabricated on indium tin oxide electrodes by a spin-coating method, and performance and microstructures of the solar cells were investigated. Decaphenylcyclopentasilane (PDPS), polymethlyphenylsilane (PMPS) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) were used for the solar cells. The conversion efficiencies of PDPS:PCBM solar cells were higher than those of PMPS:PCBM devises. Transmission electron microscopy and X-ray diffraction indicated that PDPS:PCBM layer had a nanocomposite structure.

AbstractHigh-resolution electron microscopy (HREM) analysis has contributed to the direct structure analysis of advanced nanostructured materials, of which the properties of these materials are strongly dependent on the atomic arrangements. In the present article, the direct structure analysis of nanostructured materials such as boride and oxide materials was described and the high-resolution imaging methods were applied to boron nitride nanomaterials such as nanotubes and nanoparticles. An aberration correction technique is also expected as an advanced nanostructure analysis with higher resolution. The HREM image of TlBa2Ca3Cu4O11was taken with the incident beam parallel to the a axis together with a structure model after image processing.

Abstract: Copper phthalocyanine/fullerene-based solar cells were fabricated, and the electronic and optical properties were investigated. Effects of germanium addition to the solar cells were also investigated, which resulted in increase of power conversion efficiencies of the solar cells. Nanostructures of the solar cells were investigated by transmission electron microscopy and electron diffraction, which indicated formation of Ge compound nanoparticles in the copper phthalocyanine layers. Energy levels of the solar cells were discussed from the present analysis data.

Polyaniline thin films as hole transporting layers were fabricated on transparent indium--tin-oxide electrodes by electrodeposition of aniline in an aqueous H2SO4electrolyte solution. Emerald-green polyaniline films were obtained, which showed stable redox waves. A mixed solution of polythiophene and fullerene derivative was spin-coated onto the electrodeposited polyaniline film. After the modification of titanium oxide film on the surface of the polythiophene/fullerene layer, an aluminum electrode was fabricated by vacuum deposition. The obtained solar cells generated stable photocurrent and photovoltage under light illumination.

Fluorophthlocyanine thin films were used as n-type semiconductor in organic solar cell. Heterojunction solar cells of cupper hexadecafluorophthalocyanine (F16CuPc) / copper phthalocyanine (CuPc) and F16CuPc / zinc phthalocyanine (ZnPc) deposited with PEDOT-PSS on ITO as electrode were fabricated and characterized. Comparison between CuPc and ZnPc as p-type semiconductor on photovoltaic performance was studied. Light-induced charge separation and charge transfer was investigated by current density and optical absorption. Internal microstructure in active layer was measured by transmission electron microscopy, X-ray and electron diffractions. The F16CuPc thin film in the deposited active layer worked for electron-accepting layer as n-type semiconductor. The photovoltaic performance was original in charge transfer from CuPc to F16CuPc in active layer.

High-resolution electron microscopy (HREM) analysis has contributed to the direct analysis of the atomic structures of advanced nanostructured materials, of which properties of these materials are strongly dependent on the atomic arrangements. In the present paper, the direct atomic analysis of nanostructured materials such as borides and oxide materials was described, and the HREM methods were applied to boron nitride nanomaterials such as nanotubes and nanoparticles.

Fabrication and characterization of fullerene (C60) / dibenzotetrathiafulvalene (DBTTF) solar cells were carried out. Photovoltaic and optical properties of the organic solar cells were investigated. Transmission electron microscopy, x-ray and electron diffraction confirmed that the bulk heterojunction thin films had microstructure of C60 crystal phase in DBTTF amorphous phase. The photovoltaic performance of the bulk heterojunction solar cell would be originated in the extent of electron diffusion across interface around the microstructure. Photovoltaic mechanism was discussed on the basis of experimental results.

Effects of SbI3addition to CH3NH3PbI3precursor solutions on the photovoltaic properties were investigated. TiO2/CH3NH3Pb1−xSbxI3-based photovoltaic devices were fabricated in air, and formation of a perovskite-type structure was confirmed by X-ray diffraction. The conversion efficiencies were improved by adding a small amount of Sb, and formation of PbI2was suppressed by the Sb addition.

CH3NH3PbI3(MAPbI3) perovskite solar cells with guanidinium (C(NH2)3+, GA+) are fabricated at 150 °C using 3CH3NH3I:PbCl2starting composition in ambient atmosphere, and characterized. Their photoconversion efficiencies and stabilities are improved by the addition of a small amount of GA+. Lattice volumes are increased by the addition of GA+, which confirms the occurrence of GA+substitution at the CH3NH3site. Energy gaps are decreased by the addition of GA+, which agrees well with the results of molecular orbital calculation and band calculation. The carrier trap density is reduced by the GA+addition, which suggests that lattice defects are suppressed by the GA+doping. Two‐year stabilities of the devices in ordinary air are also investigated, which indicate the effectiveness of GA addition. Photovoltaic properties of CH3NH3PbI3perovskite solar cells are improved by guanidinium (GA) addition. Lattice volumes are increased by the GA substitution at the CH3NH3site, which provides improvement of structures and electronic states, and the lattice defects of CH3NH3are also suppressed by the GA doping.

Boron nitride (BN) nanohorns were synthesized by an arc-melting method, and atomic structure models for BN nanohorns with tetragonal BN rings were proposed from high-resolution electron microscopy and image calculation. Stability and electronic structures of the BN nanohorns were investigated by molecular orbital calculations, comparing with carbon nanohorns. The calculation showed that multi-walled BN nanohorns would be stabilized by the stacking of BN nanohorns. An energy gap of BN nanohorn was calculated to be 0.80 eV, which is lower compared to those of BN clusters and nanotubes.

A promising technique to synthesize iron nanoparticles with boron nitride BN and carbon C nanocoatings was developed. Mixtures of α-Fe2O3and boron or carbon powders were employed as starting materials and were annealed at temperatures above 1273 K in a nitrogen atmosphere. Products were mainly composed of α-Fe and hexagonal BN or graphite carbon without hematite, which was confirmed by X-ray diffraction. High-resolution transmission electron microscope observation revealed that BN and C nanocapsules with iron nanoparticles of ca.300 nm in diameter were formed, and they exhibited soft magnetic properties from magnetization measurements. In addition, multi-walled BN and C nanotubes with diameters of a few hundred nanometers were produced by the present method.

A promising technique to synthesize iron nanoparticles with boron nitride (BN) and carbon (C) nanocoatings was developed. Mixtures of α-Fe₂O₃ and boron or carbon powders were employed as starting materials and were annealed at temperatures above 1273 K in a nitrogen atmosphere. Products were mainly composed of α-Fe and hexagonal BN or graphite carbon without hematite, which was confirmed by X-ray diffraction. High-resolution transmission electron microscope observation revealed that BN and C nanocapsules with iron nanoparticles of ca. 300 nm in diameter were formed, and they exhibited soft magnetic properties from magnetization measurements. In addition, multi-walled BN and C nanotubes with diameters of a few hundred nanometers were produced by the present method.

Various boron nitride (BN) and carbon (C) nanocage fullerene materials (clusters, metallofullerenes, onion, nanotubes and nanocapsules) were synthesized by arc-melting, electron-beam irradiation, chemical reaction, and self-organization. Atomic structures and structural stability of these materials were investigated by high-resolution electron microscopy, energy dispersive spectroscopy, electron energy-loss spectroscopy, molecular mechanics, molecular dynamics and molecular orbital calculations. Photoluminescence, magnetic and electronic properties of these fullerene materials were also investigated. The present work indicates that the new BN and C nanocage fullerene materials with various atomic structures and properties can be produced by various synthesis methods, and a guideline for designing the BN and C fullerene materials is summarized.

Boron nitride nanocapsules with silver nanoparticles and carbon nanocage structures with Ge and SiC nanoparticles were produced by the new chemical solution process and hybrid arc-discharge method. High-resolution electron microscopy, energy dispersive spectroscopy and X-ray diffraction showed the formation of silver and silver oxide nanoparticles encapsulated in boron nitride nanocages, which were synthesized from mixtures of boric acid, urea and silver nitrate by reduction at 300–700°C in hydrogen gas. Ge and SiC nanoparticles and nanowires encapsulated in carbon nanocapsules and nanotubes were also produced by direct current and radio frequency hybrid arc-discharge of C, Ge and Si elements. The present work indicates that the various boron nitride and carbon nanocage structures with electronic conductors, superhard materials, semiconductor nanoparticles and nanowires can be synthesized by the new chemical process and hybrid arc-discharge method, and the chemical synthesis of the boron nitride nanocapsules from the organic solution materials is a useful fabrication method for the mass production of low-dimensional nanocage structures at low temperatures compared to the ordinary arc-discharge method.

Boron nitride (BN) nanocapsules with iron oxide nanoparticles were fabricated by an arc discharge method, and the magnetic properties of these nanocapsules were investigated. High resolution electron microscopy showed that iron oxide nanoparticles of size 20nm were encapsulated by boron nitride sheets of width 4nm. Magnetization of the BN nanocapsules showed paramagnetism and the initial iron oxides showed ferromagnetism, which suggests the transformation into superparamagnetism by separating the iron oxide nanoparticles with BN sheets. The present work showed that the BN nanocapsules with magnetic nanoparticles can be produced and the effectiveness of the arc melting method was confirmed.

Boron nitride (BN) fullerenes and nanotubes were obtained by applying the arc-melting method to a powder mixture of boron and iron oxide in a nitrogen gas. BN fullerenes of size 0.7nm were observed. Angular tips of BN nanotubes of diameter 6.6nm and length 50–100nm were also observed. When using a powder mixture of boron and gold, BN fullerenes and nanotubes were not obtained. Atomic structure models for BN fullerene and nanotube were proposed, and the (BN)36cluster was found to be stable in spite of the existence of distorted six- and four-membered rings. The density of states for the cluster was calculated theoretically, and is similar to that of hexagonal BN. The prime novelty of the study is that BN fullerenes and BN nanotubes can be synthesized by a simple arc-melting method, and the stability of their atomic structure and the electronic state were predicted by theoretical calculations.

High-resolution images of C3N3.6–4.5O1.1–1.2H4.1–4.2showed nanocage and nanotube-like structures, which have cage and tube sizes in the range 10–500nm. Electron diffraction of the cage structures showed diffuse ring patterns, and carbon and nitrogen were detected, which indicates a disordered CNxstructure. Nanocrystalline grains encapsulated in CNxnanotubes and nanocapsules were also observed, and carbon, oxygen and a little nitrogen were detected. These nanocrystals showed clear diffraction reflections with ring patterns. The present work indicates that the new nanocage structures consisting of CNx-based materials can encapsulate the nanocrystals, which are expected as future functional harmonized materials.

A thermally stable Ni-based ohmic contact is one of the most attractive contact materials for developing superior GaAs devices. To understand the interface reaction between an Ni thin film and a GaAs wafer, a combined grazing-incidence and grazing-takeoff x-ray fluorescence (GIT-XRF) method was applied. Ni thin films (~10 nm in thickness) were deposited on GaAs wafers, then annealed at 373 and 473 K. When the conventional grazing-incidence XRF and grazing-exit XRF methods were separately applied to a sample annealed at 373 K, it was not possible to recognize interface reactions between Ni and GaAs. However, the small compositional change at the interface could be detected by the non-destructive GIT-XRF method. The diffusion of Ni atoms into the GaAs substrate, which was induced by heating at 473 K for 3 min, was clearly found by measuring the takeoff angle dependences of characteristic x-ray intensities at a grazing incidence angle of 2.5 mrad. Finally, the mixed Ni–GaAs layer was evaluated to be Ni5GaAs with a thickness of 15 nm by fitting calculated curves to experimental plots. Copyright © 2000 John Wiley & Sons, Ltd.

AbstractCarbon onions were produced in a transmission electron microscope by electron beam irradiation of amorphous carbon with Pd clusters. High-resolution electron microscopy showed Pd atoms were intercalated between the graphite onion sheets, and the structural model for the intercalation was proposed. HREM images and diffraction patterns calculated for the model agrees well with the observed ones. The present work indicates that the electron-beam irradiation to amorphous carbon with Pd clusters is an effective method for the formation of intercalated onions.

AbstractFormation of carbon nanocapsules with various clusters (SiC, Au, Fe. Co. Ge. and GeO2) by polymer pyrolysis was investigated, and nanocapsules with SiC and Au nanoparticles were produced by thermal decomposition of polyvinyl alcohol at −500°C in Ar gas atmosphere. The formation mechanism of nanocapsules and a structural model for the nanocapsule/SiC interface were proposed. In addition, carbon clusters were formed at the surface of carbon nanocapsules, and carbon onions were produced by electron irradiation of amorphous carbon produced from polyvinyl alcohol. The present work indicates that the pyrolysis of polymer materials with clusters is a useful fabrication method for the mass-production of carbon nanocapsules and onions at low temperatures compared to the ordinaly are discharge method.

AbstractBoron nitride nanocapsules with gold, iron oxide and germanium nanoparticles were produced. High-resolution electron microscopy and electron energy-loss spectroscopy showed the gold, iron oxide and germanium nanoparticles were encapsulated in the boron nitide sheets. Weak peaks of photoluminescence spectrum were observed from the nanocapsules with germanium nanoparticles. The present work indicates that the boron nitide nanocapsules with conducting, magnetic and semiconductor nanoparticles can be produced by are melting method, and models for the formation mechanism and nano-structures of the boron nitide nanocapsule were proposed.

TiO2/CH3NH3PbI3-based photovoltaic devices were fabricated by a spin-coating method using a mixture solution of niobium(V) ethoxide, and the effects of niobium (Nb) addition to TiO2layers were investigated. The lattice distance and energy gap of the TiO2were almost same after Nb addition. The elemental mapping and sheet resistance measurements indicated a wide distribution of Nb and Ti, and a decrease in sheet resistance by Nb addition. The external quantum efficiency and internal quantum efficiency increased by Nb addition to compact TiO2and mesoporous TiO2layers, which resulted in an increase in the current density and conversion efficiency of the cell.

Thin films of [60]fullerene–1,2-diaminoethane adduct microparticles (C60P) were fabricated via a liquid/liquid interface precipitation. The energy level of the lowest unoccupied molecular orbital (LUMO) of the C60P was evaluated by electrochemical analysis. The additional tetraphenylporphyrin substantially enhanced the photocurrent from the C60P-thin-film-modified electrode.

We report here new types of suprastructure products consisting of C60-ethylenediamine microparticles and silver nanoparticles that were loaded onto the surfaces of the microparticles by electrostatic adsorption. The suprastructure products could be deposited on the surface of an indium tin oxide electrode by electrostatic deposition. These modified electrodes generated cathodic photocurrents in the presence of ascorbic acid and oxygen. The photocurrent generation behavior implies an ensemble of the electron-transfer processes of silver-nanoparticle-mediated electron transfer acting in the cathodic direction and plasmon-induced charge separation acting in the anodic direction.

The structure of an iron oxide clusterimplanted into zeolite Y (depicted) was determined by a combination of high‐resolution transmission electron microscopy, image processing and selected area electron diffraction. The six‐iron cluster is located in the sodalite cage of the zeolite.

Although it is difficult to determine the atomic arrangement of boron, carbon, and oxygen in the solid clusters and oxides because of their low atomic number, it is believed that the high-resolution images should have “some” information for disordering, ordering, and doping atomic positions in these materials. In the present work, we obtained and predicted the information for disordering, ordering, and doping atomic positions in YB56, HgTlBa2CuOx, and N@C60 from digital HREM images. Residual indices (RHREM = Σ ¦Iobs − Ical¦/ ΣIobs) were used for image analysis. Difference images between observed and simulated images were also calculated for structure analysis. The present work indicates that this kind of atomic detection would be very useful for evaluation of local atomic positions in the crystal with light elements such as boron, carbon, nitrogen and oxygen atoms.