Excitons in self-organized layered perovskite films prepared by the two-step growth process

Thin films of microcrystalline (C₈H₁₇NH₃)₂PbBr₄ were prepared by a two-step growth process as follows: (1) deposition of PbBr₂ films on substrates and (2) self-organized growth of layered perovskite compounds by exposing the PbBr₂ film to C₈H₁₇NH₃Br vapor in a vacuum chamber. As-synthesized (C₈H₁₇NH₃)₂PbBr₄ films were characterized by using X-ray diffraction, temperature dependence in optical absorption and photoluminescence spectra. (C₈H₁₇NH₃)₂PbBr₄ films created by this synthesis approach were found to microcrystalline form, single phase and highly oriented with a c-axis perpendicular to the substrate surface. (C₈H₁₇NH₃)₂PbBr₄ films showed clear exciton absorption and photoluminescence even at room temperature in the near-ultraviolet region. Exciton binding energy of (C₈H₁₇NH₃)₂PbBr₄ was estimated about 200 meV.     

Ultraviolet Photoelectron Spectroscopy of Two Titanium Metal Atoms Encapsulated Metallofullerenes, Ti2@C80 and Ti2@C84

Ultraviolet photoelectron spectra (UPS) of Ti₂@C₈₀ (mixture of two isomers) and two Ti₂@C₈₄ isomers excited by synchrotron radiation light source are presented. The spectra of Ti₂@C₈₀ are complicated compared with those of other metallofullerenes, which is considered with an aid of molecular orbital (MO) calculation. The photoelectron spectra of two Ti₂@C₈₄ isomers are fairly analogous with each other and show less structure than that of Sc₂@C₈₄. This suggests that the symmetry of two isomers differs from D_2d symmetry of Sc₂@C₈₄.     

Current‐Induced Nucleation and Annihilation of Magnetic Skyrmions at Room Temperature in a Chiral Magnet

A magnetic skyrmion is a nanometer‐scale magnetic vortex carrying an integer topological charge. Skyrmions show a promise for potential application in low‐power‐consumption and high‐density memory devices. To promote their use in applications, it is attempted to control the existence of skyrmions using low electric currents at room temperature (RT). This study presents real‐space observations for the current‐induced formation and annihilation of a skyrmion lattice (SkL) as well as isolated skyrmions in a microdevice composed of a thin chiral magnet Co₈Zn₉Mn₃ with a Curie temperature, T _C ≈ 325 K, above RT. It is found that the critical current for the manipulation of Bloch‐type skyrmions is on the order of 10⁸ A m^?2, approximately three orders of magnitude lower than that needed for the creation and drive of ferromagnetic (FM) domain walls in thin FM films. The in situ real‐space imaging also demonstrates the dynamical topological transition from a helical or conical structure to a SkL induced by the flow of DC current, thus paving the way for the electrical control of magnetic skyrmions.     

Nuclear Magnetism of Submonolayer Solid 3He on Graphite

Submonolayer solid ³ He adsorbed on graphite has been studied with NMR measurement down to the order of 0.1 mK. The magnetization curves are well fitted to the Curie-Weiss law in the whole investigated density region (5.0 nm ^–2 - 8.5 nm ^–2 ). The obtained Weiss temperatures are found to be positive at a commensurate phase and an incommensurate one. However they are negative in the intermediate density region, which suggests the existence of an antiferromaynetic phase also in the Submonolayer. The change from an antiferro to a ferromagnetic behavior at around 7.3 nm ^–2 is similar to that of the second layer, and can be explained by a multiple spin exchange model. Therefore the ferromagnetic behavior in the second layer is not necessarily due to the liquid overlayer. While the ferromagnetic behavior at the phase is not reproduced by a simple density dependence of competing multiple exchange interactions and indicates the importance of the corrugation potential from the graphite substrate.     

Capacitive touchscreen‐integrated electrostatic tactile display with localized sensation

An electrostatic tactile display with a projected capacitive touchscreen integrated into a single panel was demonstrated. Every electrode on the panel is driven for both tactile presentation and the touch sensor. The functions are both time and spatially multiplexed, and a reference–node‐driven high‐pass filter in the touch controller filters out the noise from the tactile driving signals.     

Microstructure and Photoluminescence Properties of Mg-Doped BaTiO3:Pr3+ Phosphor

The photoluminescence of Mg-doped BaTiO₃:Pr³⁺ (Pr³⁺: 0.1 mol%) ceramics was investigated by changing the doping concentration of Mg and the sintering temperature. The results indicated that the intensity of red emission due to the ¹ D ₂→³ H ₄ transition of Pr³⁺ exhibited significant dependence on both the Mg doping content and the sintering temperature; the strongest red emission intensity was observed for 2.0 mol% Mg-doped ceramics sintered at 1050°C. An interpretation of the results obtained was made in terms of the changes in the crystal structure and microstructure of the ceramics.     

Thermal properties of novel supramolecular polymer networks based on poly(4-vinylpyridine) and disulfonic acids

Novel supramolecular polymer networks were prepared by the reaction of poly(4-vinylpyridine) (P4VP) with 1,5-naphthalenedisulfonic acid (NDS), 1,3-propanedisulfonic acid (PDS), or adipic acid (AA). The IR and XPS analyses of the polymer networks revealed that the P4VP/NDS complex has a higher ionic interaction between pyridinium cation and sulfonate anion than the P4VP/PDS complex, and that hydrogen bonding interaction between pyridine and carboxylic acid predominantly contributes for the P4VP/AA complex. When the glass transition temperatures of P4VP and P4VP/proton donor (1/1) complexes are compared, the higher order was P4VP/NDS>P4VP/PDS>P4VP>P4VP/AA, in agreement with a higher degree of ionic interaction. The P4VP/PDS complex had a melting endothermic peak in the DSC thermograms, which was not observed for the P4VP/NDS complex. The thermal decomposition temperature of the P4VP complexes is also investigated in relation to the intermolecular interaction.     

Composition depth profile analysis of bulk heterojunction layer by time-of-flight secondary ion mass spectrometry with gradient shaving preparation

Composition depth profile analysis of bulk heterojunction (BHJ) layer was performed by time-of-flight secondary ion mass spectrometry with gradient shaving preparation. The BHJ layer comprised of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61butyric acid methyl ester (PCBM) was formed on the substrate coated with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) followed by annealing. The P3HT component increased toward the top surface in the BHJ layer. In addition, C₈H₇SO₃⁻ was detected inside the BHJ layer, suggesting penetration of PSS. P3HT was uniformly distributed in the BHJ layer without PEDOT:PSS. The P3HT-rich distribution in the top surface may be attributed to PSS penetration.