Efficiency of exciton dissociation at internal organic interfaces beyond harmonic approximation

Understanding the mechanism of the efficient exciton dissociation in multicomponent systems belongs to the most prominent challenges in applied soft-matter physics. The model with discrete dipoles along the internal interface between the different material components is often considered as promising to account for the exciton dissociation. However, the dissociation efficiency in the framework of this model has been so far calculated only within the harmonic approximation. In the current article we calculate the dissociation efficiency in the dipolar model beyond the harmonic approximation and show that the exciton dissociation probability appears drastically larger than assumed so far. We also consider the effect of a finite spatial extent of the dipole charges and show that if the charges cannot be treated as point-like species, harmonic approximation is not applicable.     

Economic Assessment of the Hydrogenation of CO2 to Liquid Fuels and Petrochemical Feedstock

To remove high concentrations of CO₂ from the off‐gas of coal‐driven power plants, a new process was proposed. The catalytic hydrogenation of the CO₂ leads to the production of C₂ – C₄ (petrochemical feedstock) and liquid C₅₊ hydrocarbons (fuel). Thus, environmentally harmful CO₂ may be converted sustainably to useful products. On the basis of a process flow sheet, the costs for processing the CO₂ are estimated for different plant sizes. The price of hydrogen contributes significantly to the overall production costs. Further price reductions may be achieved by final engineering optimization of the process as a whole and specific unit operations.     

Thermoelectric Properties of Nanostructured Bismuth-Doped Lead Telluride Bi x (PbTe)1−x Prepared by Co-Ball-Milling

In this work we present a simple method to synthesize nanostructured, bismuth-doped lead telluride by co-ball-milling. The obtained nanopowders were compacted via either a cold pressing/annealing approach or by hot pressing. The two compacting methods were compared regarding sample density. Series with bismuth content up to 6 at.% were characterized by measuring the thermoelectric transport properties over a wide temperature range between 123 K and 773 K using two different techniques for the Seebeck coefficient and electrical conductivity. A decreasing thermal conductivity and increasing electrical conductivity were found with increasing doping level. The best results were obtained for samples with 5 at.% and 6 at.% bismuth, showing a maximum ZT value of 1.1 at 773 K. Transmission electron microscopy study was performed to analyze the microstructure of the nanopowders, suggesting that, in addition to n-type doping of the lead telluride matrix, segregation effects occur and the samples consist of multiple phases.     

Defect engineering in semiconducting oxides: Control of ZnO surface potential via temperature and oxygen pressure

The technological usefulness of a semiconductor often depends on the types, concentrations, charges, spatial distributions, and mobilities of the atomic‐scale defects it contains. For semiconducting metal oxides, defect engineering is relatively new and involves complex transport and reaction networks. Surface‐based methods hold special promise in nanostructures where surface‐to‐volume ratios are high. This work uses photoreflectance augmented by X‐ray photoelectron spectroscopy to show that the surface potential V_S for Zn‐terminated ZnO(0001) can be manipulated over a significant range 54.97–79.08 kJ/mol (0.57–0.82 eV) via temperature and the partial pressure of O₂. A defect transport model implies this variation in V_S should affect the injection rate of oxygen interstitials by a factor of three. Such injection plays an important role in controlling the concentrations of oxygen vacancies deep in the bulk, which often prove troublesome as trapping centers in photocatalysis and photovoltaics and as parasitic emitters in light‐emitting devices. © 2015 American Institute of Chemical Engineers AIChE J, 62: 500–507, 2016     

A 1.544-Mb/s CMOS line driver for a 22.8-Ω load

A CMOS line driver for high-speed data communication according to the T1 and CEPT recommendations is presented. The differential output swing is 7.2 V_pp on a load of 22.8 Ω from a single 5-V supply. A novel quiescent current control scheme is used. The driver occupies an area of 6.5 mm² using a 2-μm p-well CMOS technology     

Tapered waveguide InGaAs/InGaAsP multiple-quantum-well lasers

The use of ultrathin etch-stop techniques to expand the vertical optical mode size adiabatically in 1.5-μm InGaAs/InGaAsP MQW lasers using a tapered-core passive intracavity waveguide structure is discussed. 30% differential quantum efficiency out the tapered facet, far-field FWHM of ~12° and a butt-coupling efficiency into a cleaved fiber of -4.2 dB, with -1-dB alignment tolerances of ~±3 μm, were achieved