Cotunneling in the \nu = 5/2 fractional quantum Hall regime

We show that cotunneling in the 5/2 fractional quantum Hall regime allows us to test the Moore-Read wave function, proposed for this regime, and to probe the nature of the fractional charge carriers. We calculate the cotunneling current for electrons that tunnel between two quantum Hall edge states via a quantum dot and for quasiparticles with fractional charges e/4 and e/2 that tunnel via an antidot. While electron cotunneling is strongly suppressed, the quasiparticle tunneling shows signatures characteristic of the Moore-Read state. For comparison, we also consider cotunneling between Laughlin states, and find that electron transport between Moore-Read states and between Laughlin states at filling factor 1/3 have identical voltage dependences

The Effect of Electrical Polarization on Electronic Structure in LSM Electrodes: An Operando XAS, RIXS and XES Study

The influence of electrical polarization on Mn in La0.5Sr0.5MnO3±δ electrodes has been investigated by operando High Energy Resolved Fluorescence Detected X-Ray Absorption Near-Edge Structure (HERFD-XANES) spectroscopy, Kβ X-ray Emission Spectroscopy (XES) and Resonant Inelastic X-ray Scattering (RIXS) at the Mn K-edge. The study of polarization induced changes in the electronic properties and structure has been carried out at 500°C in 10–20% O2 with electrical polarization applied in the range from −850 mV to 800 mV. Cathodic polarizations in the range −600 mV to −850 mV induced a shift in the Mn K edge energy towards lower energies. The shift is assigned to a decrease in the average Mn oxidation state, which based on Kβ XES changes from 3.4 at open circuit voltage to 3.2 at −800 mV applied potential. Furthermore, RIXS rendered pronounced changes in the population of the Mn 3d orbitals, due to filling of the Mn d-orbitals during the cathodic polarization. Overall, the study experimentally links the electrical polarization of LSM electrodes to the structural and electronic properties of Mn - these properties are expected to be of major importance for the electrocatalytic performance of LSM electrode towards the oxygen reduction reaction

Demonstrating the high Voc potential of PEDOT:PSS/c-Si heterojunctions on solar cells

In this study, we demonstrate the high surface passivation quality of PEDOT:PSS/c-Si junctions for the first time on solar cell level, reaching a record high Voc value of 688 mV after full-area metallization of the PEDOT:PSS. We achieve this by combining the PEDOT:PSS hole-selective layer at the rear of the crystalline silicon wafer with a well-passivating electron-selective a-Si:H(i/n) layer stack at the front. Our results clearly prove the excellent hole selectivity of PEDOT:PSS on crystalline silicon. © 2017 The Authors. Published by Elsevier Ltd

An Artificially Lattice Mismatched Graphene/Metal Interface: Graphene/Ni/Ir(111)

We report the structural and electronic properties of an artificial graphene/Ni(111) system obtained by the intercalation of a monoatomic layer of Ni in graphene/Ir(111). Upon intercalation, Ni grows epitaxially on Ir(111), resulting in a lattice mismatched graphene/Ni system. By performing Scanning Tunneling Microscopy (STM) measurements and Density Functional Theory (DFT) calculations, we show that the intercalated Ni layer leads to a pronounced buckling of the graphene film. At the same time an enhanced interaction is measured by Angle-Resolved Photo-Emission Spectroscopy (ARPES), showing a clear transition from a nearly-undisturbed to a strongly-hybridized graphene $\pi$-band. A comparison of the intercalation-like graphene system with flat graphene on bulk Ni(111), and mildly corrugated graphene on Ir(111), allows to disentangle the two key properties which lead to the observed increased interaction, namely lattice matching and electronic interaction. Although the latter determines the strength of the hybridization, we find an important influence of the local carbon configuration resulting from the lattice mismatch.Comment: 9 pages, 3 figures, Accepted for publication in Phys. Rev.

Advances in the Surface Passivation of Silicon Solar Cells

AbstractThe surface passivation properties of aluminium oxide (Al2O3) on crystalline Si are compared with the traditional passivation system of silicon nitride (SiNx). It is shown that Al2O3 has fundamental advantages over SiNx when applied to the rear of p-type silicon solar cells as well as to the p+ emitter of n-type silicon solar cells. Special emphasis is paid to the transfer of Al2O3 into industrial solar cell production. We compare different Al2O3 deposition techniques suitable for mass production such as ultrafast spatial atomic layer deposition, inline plasma-enhanced chemical vapour deposition and reactive sputtering. Finally, we review the most recent cell results with Al2O3 passivation and give a brief outlook on the future prospects of Al2O3 in silicon solar cell production

Morphological evolution of electrochemically plated stripped lithium microstructures by synchrotron X ray phase contrast tomography

Due to its low redox potential and high theoretical specific capacity, Li metal has drawn worldwide research attention because of its potential use in next generation battery technologies such as Li S and Li O2. Unfortunately, uncontrollable growth of Li microstructures LmSs, e.g., dendrites, fibers during electrochemical Li stripping plating has prevented their practical commercialization. Despite various strategies proposed to mitigate LmS nucleation and or block its growth, a fundamental understanding of the underlying evolution mechanisms remains elusive. Herein, synchrotron in line phase contrast X ray tomography was employed to investigate the morphological evolution of electrochemically deposited dissolved LmSs nondestructively. We present a 3D characterization of electrochemically stripped Li electrodes with regard to electrochemically plated LmSs. We clarify fundamentally the origin of the porous lithium interface growing into Li electrodes. Moreover, cleavage of the separator caused by growing LmS was experimentally observed and visualized in 3D. Our systematic investigation provides fundamental insights into LmS evolution and enables us to understand the evolution mechanisms in Li electrodes more profoundl

Surface passivation of silicon solar cells using industrially relevant Al2O3 deposition techniques

The next generation of industrial silicon solar cells aims at efficiencies of 20% and above. To achieve this goal using ever-thinner silicon wafers, a highly effective surface passivation of the cell front and rear is required. In the past, finding a suitable dielectric layer providing a high-quality rear passivation has been a major challenge. Aluminium oxide (Al2O3) grown by atomic layer deposition (ALD) has only recently turned out to be a nearly perfect candidate for such a dielectric. However, conventional ALD is limited to deposition rates well below 2nm/min, which is incompatible with industrial solar cell production. This paper assesses the passivation quality provided by three different industrially relevant techniques for the deposition of Al2O3 layers, namely high-rate spatial ALD, plasma-enhanced chemical vapour deposition (PECVD) and reactive sputtering