Intrinsic optical gain of ultrathin silicon quantum wells from first-principles calculations

Optical gains of ultrathin Si(001) quantum wells are calculated from first principles, and found to be positive because of an intrinsic quantum confinement effect. The gain of the ultrathin silicon film is comparable to that of the bulk GaAs if the carrier density is large enough. The impact of surface structure of the silicon film on the efficiency of light emission is also investigated and we found that SiO2 crystal that forms a strainless connection with a Si(001) surface such as quartz enhances optical gain

Spin-density functional study of the organic polymer dimethylaminopyrrole: A realization of the organic periodic Anderson model

While the periodic Anderson model (PAM) has been recognized as a good model for various heavy f-electron systems, here we design a purely organic polymer whose low-energy physics can be captured by PAM. By means of the spin density functional calculation, we show that polymer of dimethylaminopyrrole is a candidate, where its ground state can indeed be magnetic depending on the doping. We discuss the factors favoring ferromagnetic ground state.Comment: 8 pages, 8 figure

収着冷凍に用いる金属塩添着複合材料の水蒸気収着挙動に関する研究

13301甲第4419号博士(工学)金沢大学博士論文要旨Abstrac

収着冷凍に用いる金属塩添着複合材料の水蒸気収着挙動に関する研究

13301甲第4419号博士(工学)金沢大学博士論文本文Ful

Water vapor sorption characteristics of calcium chloride-anodized alumina composites

In this study, calcium chloride-anodized alumina composites were examined for water vapor sorption properties. Porous alumina host matrices for calcium chloride impregnation were prepared by anodizing aluminum plates in an oxalic acid bath or a sulfuric acid bath. CaCl2-alumina composites were obtained through calcination of the anodic alumina film impregnated with a CaCl2 solution at 473 or 773 K. XRD analyses indicated that the type of host matrix and the calcination temperature made an effect on crystal states of calcium chloride in the composite layer. The composite calcined at 473 K, of which the host matrix was oxalic-acid anodized alumina film, contained calcium chloride anhydrate crystals. Water vapor sorption experiments showed that the composite with crystalline calcium chloride sorbed water vapor well, and its sorption isotherm had a shape similar to that of bulk CaCl2. Therefore, the water sorption behavior of the CaCl2-alumina composite strongly depends on the crystal states of calcium chloride in anodized alumina layer. © 2016 The Society of Chemical Engineers, Japan

Deposition of thick, rigid and size-controlled silica particle layer on aluminum sheet for water vapor adsorption

Toward the development of a new adsorbent heat exchanger of adsorption chillers, silica-coated aluminum sheets were prepared by the combination of sol-gel and electrophoretic deposition techniques. Silica sols were synthesized by the hydrolysis of tetraethoxysilane precursor in an ethanol solution, and then a silica layer was directly formed on an aluminum sheet by electrophoretic deposition of the silica sols. The silica-coated aluminum sheets were subjected to the aging treatment in an ammonia water bath with a DC electric field. This aging treatment was found to be very effective to form rigid silica layer on aluminum sheet. It was found that the obtained layer was composed of monodisperse and spherical submicron-sized silica particles. Sodium dodecyl sulfate (SDS) in the silica sol solution played an important role in controlling the deposited amount of silica particles as well as their sizes. The particle size increased from 0.10 to 0.83 µm with an increase in SDS concentration. For the silica-coated aluminum sheet prepared at a pH value of 10.6 and a SDS concentration of 0.05 mass%, the deposited amount reached a maximum value of 19.8 mg cm−2, which was much higher than those reported by Kishida et al. (1994). The prepared composites were evaluated for the characteristics of water vapor adsorption through volumetric experiments. The results of adsorption experiments showed that the composite with a higher silica content adsorbed a larger amount of water vapor in the relative pressure range below 0.3. © 2017 Elsevier LtdEmbargo Period 12 month

Gate-induced band ferromagnetism in an organic polymer

We propose that a chain of five-membered rings (polyaminotriazole) should be ferromagnetic with an appropriate doping that is envisaged to be feasible with an FET structure. The ferromagnetism is confirmed by a spin density functional calculation, which also shows that ferromagnetism survives the Peierls instability. We explain the magnetism in terms of Mielke and Tasaki's flat-band ferromagnetism with the Hubbard model. This opens a new possibility of band ferromagnetism in purely organic polymers.Comment: 4 pages, 7 figure

Flat-Band Ferromagnetism in Organic Polymers Designed by a Computer Simulation

By coupling a first-principles, spin-density functional calculation with an exact diagonalization study of the Hubbard model, we have searched over various functional groups for the best case for the flat-band ferromagnetism proposed by R. Arita et al. [Phys. Rev. Lett. {\bf 88}, 127202 (2002)] in organic polymers of five-membered rings. The original proposal (poly-aminotriazole) has turned out to be the best case among the materials examined, where the reason why this is so is identified here. We have also found that the ferromagnetism, originally proposed for the half-filled flat band, is stable even when the band filling is varied away from the half-filling. All these make the ferromagnetism proposed here more experimentally inviting.Comment: 11 pages, 13figure