We study the spin ordering of a quantum dot defined via magnetic barriers in an interacting quantum spin Hall edge. The spin‐resolved density–density correlation functions are computed. We show that strong electron interactions induce a ground state with a highly correlated spin pattern. The crossover from the liquid‐type correlations at weak interactions to the ground state spin texture found at strong interactions parallels the formation of a one‐dimensional Wigner molecule in an ordinary strongly interacting quantum dot.
Ordered Sr2CrReO6 has been synthesized recently. It is measured to be ferrimagnetic semiconductor, in contrary to the previous reports of metallic properties. To solve the discrepancy, we have investigated the compound by using the density functional theory. The semiconducting behavior is reproduced by including the electron correlation and spin–orbit coupling simultaneously. The calculated band gap is 0.22 eV, close to the experimental value of 0.21 eV. A large orbital moment of 0.69µB is found for Re, which is caused by the Coulomb‐enhanced spin–orbit coupling. By applying pressure, a semiconductor to half‐metal transition is observed through 5% volume compression.
The fabrication of titania nanostructures with hierarchical order of different structural levels is investigated. The nanostructures are prepared with a diblock‐copolymer assisted sol–gel process. By iterative spin‐coating of the solution onto silicon substrates a thin polymer‐nanocomposite film is deposited and transformed to purely anatase titania nanostructures via calcination. In total, this procedure is repeated three times on top of the substrate. The approach is monitored with grazing incidence small angle X‐ray scattering after each fabrication step. With scanning electron microscopy the final hierarchical structure is imaged. From the characterization different structural levels are clearly identified.
The metastability of the bixbyite‐ and corundum‐type In2O3 polymorphs up to 33 GPa (at room temperature) is shown. While compressed (in diamond anvil cells) and laser‐heated, both polymorphs undergo a phase transition to the Rh2O3‐II‐type structure (space group Pbcn, No. 60). The direct transition from bixbyite to Rh2O3‐II structure has not yet been observed for any other oxide.
The possibility of multiferroicity arising from charge ordering in LuFe2O4 and structurally related rare earth ferrites is reviewed. Recent experimental work on macroscopic indications of ferroelectricity and microscopic determination of coupled spin and charge order indicates that this scenario does not hold. Understanding the origin of the experimentally observed charge and spin order will require further theoretical work. Other aspects of recent research in these materials, such as geometrical frustration effects, possible electric‐field‐induced transitions, or orbital order are also briefly treated.
The properties of transition‐metal (V, Cr, Mn, Fe, Co, Ni) δ‐doped ZnO are reported based on ab‐initio electronic structure calculations where the on‐site electronic correlations are included using the Hubbard parameters. The calculated electronic and magnetic properties are considerably altered with respect to usual band‐structure calculations. Most of the studied systems are found to be either half‐metals or ferromagnetic/antiferromagnetic semiconductors and thus can be employed in a variety of spintronic applications as spin‐filter materials.
We demonstrate the fabrication of a solid state heterojunction photovoltaic device with solution‐processed graphene oxide (GO) and n‐Si. Partially reduced GO with a high optical gap (2.8 eV) was spin‐coated on the n‐Si substrate and a heterojunction device was fabricated with the structure of Au/pr‐GO/n‐Si. In the fabricated device, incident light was transmitted through the thin GO film to reach the junction interface, generating photoexciton, and thereby a photovoltaic action was observed. By means of a built‐in electric potential at the GO/n‐Si junction, photoexcited electrons and holes can be separated, transported and collected at the electrodes.
By means of first‐principles calculations we predict the stability of silicene as buckled honeycomb lattice on passivated substrates of group‐IV(111)1 × 1 surfaces. The weak van‐der‐Waals interaction between silicene and substrates does not destroy its linear bands forming Dirac cones at the Brillouin zone corners. Only very small fundamental gaps are opened around the Fermi level.
A facile metal catalyst free route to synthesize boron doped (0.6%–1.0%) carbon nanotubes via ceramic nanowires in which the formation of the nanowires (probably serving as templates), the carbon nanotubes and their doping all occur unanimously in the reaction, is presented.
Interaction between negatively charged Nafion® and a positively charged polybenzimidazole‐decorated carbon nanotube leads to the formation of an ionic complex with high charge density for proton conduction, which can lead to an improvement in transport properties. Here we investigate the high‐temperature and low‐humidity proton conductivity of this nanocomposite membrane as a potential membrane for fuel cell applications.
Spin crossover compounds are considered to be a viable alternative for creating display, memory and switching devices due to the bistability of their magnetic, optical, mechanical and electrical properties. This Letter presents the study of the dielectric and transport properties of the [Fe(Htrz)2(trz)](BF4) (Htrz = 1H‐1,2,4‐triazole) complex in a wide temperature and frequency range. Our results reveal a singular behavior of the dielectric modulus upon the spin transition in conjunction with the switching of the conductivity between the high spin and low spin states.
A new method for fabricating carbon nanotube‐conducting polymer (CNT‐CP) composite single nanowires is reported. The method developed is highly efficient, reliable, and economical because it obviates the time consuming process of template fabrication and the post‐synthesis task of positioning nanowires. Single nanowires with diameters of 50‐500 nm are fabricated between electrodes, self‐templated by dielectrophoresis and electropolymerization. Fabrication of an individually addressed nanowire array with cantilever electrodes on a microchip is demonstrated.
The authors describe an organic complementary inverter with N,N′‐ditridecyl‐3,4,9,10‐perylenetetracarboxylic diimide as an n‐type semiconductor and pentacene as a p‐type semiconductor. Each transistor of the inverter exhibited high carrier mobility: 1.62 cm2/Vs for an n‐type drive transistor and 0.57 cm2/Vs for a p‐type switch transistor. The gain of the inverter reached 125. Another inverter using Ta2O5 as a high κ gate dielectric performed well with a gain of 500 and an operation voltage of only 5 V.
We report the fabrication procedure and the characterization of an Al0.3Ga0.7As solar cell containing high‐density GaAs strain‐free quantum dots grown by droplet epitaxy. The production of photocurrent when two sub‐bandgap energy photons are absorbed simultaneously is demonstrated. The high quality of the quantum dot/barrier pair, allowed by the high quality of nanostructured strain‐free materials, opens new opportunities for quantum dot based solar cells.
Metallic single‐walled carbon nanotubes (m‐SWCNTs) with excellent conductivity and transparency are considered to be eminent electrode materials. However, it still remains a challenge to separate m‐SWCNTs by their diameters. As reported in this Letter, by effective purification treatment of SWCNTs, we succeeded in achieving diameter separation of m‐SWCNTs using gel column chromatography. TEM and Raman characterizations revealed that metal catalysts and amorphous carbon on tube surfaces were largely reduced, which contributed to the diameter separation of m‐SWCNTs.
A high‐stability Eu complex has been achieved by coating with a silica glass via a low temperature sol–gel process using deuterated methanol. A three‐dimensional glass network protects the Eu complex from free oxygen and/or water to change the ligand structure. In addition, the chemical bond of the deuterated Eu complex is more stable than that of the conventional Eu complex. Therefore, we achieved a high‐thermal‐stability Eu complex encapsulated by a sol–gel derived silica glass using deuterated methanol instead of ethanol.
The BOSCO solar cell represents a bifacial structure with double‐sided collection. The structure allows the use of standard module interconnection technology and favours the use of material with low to medium diffusion length and low resistivity for maximum benefit towards other structures, such as Al‐BSF and PERC. Within this work, we present first results on different multicrystalline silicon materials yielding a monofacial efficiency of 17.4% on large‐area wafers from block‐cast mc‐Si. This value represents a gain of ～0.7%abs compared to Al‐BSF cells processed in parallel. The applicability for bifacial operation is demonstrated by a significantly increased quantum efficiency for rear side illumination. These results make the BOSCO solar cell concept a promising candidate to further boost the output of utility‐scale PV plants even when using low‐cost wafers of low to medium diffusion length material.
We demonstrate the self‐catalyst growth of vertically aligned InAs nanowires on bare Si(111) by droplet epitaxy. The growth conditions of indium droplets suitable for nucleation and growth of nanowires have been identified. We have then realized vertically aligned and non‐tapered InAs nanowires on bare Si(111) substrates through optimal indium droplets. It was found that the lateral dimensions and density of nano‐wires are defined by the indium droplets. This technique unravels a controllable, cost‐effective and time‐efficient route to fabricating functional monolithic hybrid structures of InAs nanowires on silicon.
