Macro- and micro-strain in GaN nanowires on Si(111)

We analyze the strain state of GaN nanowire ensembles by x-ray diffraction. The nanowires are grown by molecular beam epitaxy on a Si(111) substrate in a self-organized manner. On a macroscopic scale, the nanowires are found to be free of strain. However, coalescence of the nanowires results in micro-strain with a magnitude from +-0.015% to +-0.03%.This micro-strain contributes to the linewidth observed in low-temperature photoluminescence spectra

Transforming Diagrams' Semantics to Text for Visually Impaired

Using models and diagrams is a very useful and effective tool for representing information and systems in a graphical form to communicate and understand them better. On the other hand, graphical representations bring extra cognitive load and the process for understanding the diagrams is long and tedious in most cases for the visually impaired. To solve this problem, semantics of the diagrams should be converted to a different format that is both human and machine readable as well as communicable for the visually impaired. Most existing diagramming tools are not easily usable for the visually impaired as a tool for creating and using diagrams. In this paper, we propose an online system for defining specific diagrams and converting their semantics to text which can have a speech output for the visually impaired. We present analysis and design of this online system as well as a proof of concept prototype implementation. The prototype system provides create, save, load and transform features and tested with participants to recreate the diagrams using the automatically generated text output. Our case study showed that the results are very promising and the proposed solution can provide a way to correctly and accurately represent the information in diagrams textually

2D PbS Nanosheets Synthesis and Their Applications as Field Effect Transistors or Solar Cells

Two-dimensional, solution-processable semiconductor materials are interesting for low-cost electronic applications [1]. We demonstrate the synthesis of lead sulfide nanosheets and how their size, shape and height can be tuned by varying concentrations of pre-cursors, ligands and by varying the reaction temperature. Especially, the charge carrier confinement in the nanosheets' height adjustable from 2 to 20 nm has a decisive impact on their electronic properties. This is demonstrated by their use as conduction channel in a field effect transistor [2]. Recently we also showed that especially thin nanosheets show a high carrier multiplication (CM) efficiency [3] which could make them, through the confinement induced band gap and high photoconductivity, very attractive for application in photovoltaic devices. We are already able to manufacture photovoltaic devices out of single nanosheets which show promising results

2D PbS Nanosheets Synthesis and Their Applications as Field Effect Transistors or Solar Cells

Two-dimensional, solution-processable semiconductor materials are interesting for low-cost electronic applications [1]. We demonstrate the synthesis of lead sulfide nanosheets and how their size, shape and height can be tuned by varying concentrations of pre-cursors, ligands and by varying the reaction temperature. Especially, the charge carrier confinement in the nanosheets' height adjustable from 2 to 20 nm has a decisive impact on their electronic properties. This is demonstrated by their use as conduction channel in a field effect transistor [2]. Recently we also showed that especially thin nanosheets show a high carrier multiplication (CM) efficiency [3] which could make them, through the confinement induced band gap and high photoconductivity, very attractive for application in photovoltaic devices. We are already able to manufacture photovoltaic devices out of single nanosheets which show promising results

Access Pricing, Competition, and Incentives to Migrate From“Old” to “New” Technology - Harvard Kennedy School of Government RWP11-029

In this paper, we analyze the incentives of an incumbent and an entrant to migrate from an “old” technology to a “new” technology, and discuss how the terms of wholesale access affect this migration. We show that a higher access charge on the legacy network pushes the entrant firm to invest more, but has an ambiguous effect on the incumbent’s investments, due to two conflicting effects: the wholesale revenue effect, and the business migration effect. If both the old and the new infrastructures are subject to ex-ante access regulation, we also find that the two access charges are positively correlated

Access regulation and the transition from copper to fiber networks in telecoms

In this paper we study the impact of different forms of access obligations on firms’ incentives to migrate from the legacy copper network to ultra-fast broadband infrastructures. We analyze three different kinds of regulatory interventions: geographical regulation of access to copper networks–where access prices are differentiated depending on whether or not an alternative fiber network has been deployed; access obligations on fiber networks and its interplay with wholesale copper prices; and, finally, a mandatory switch-off of the legacy copper network–to foster the transition to the higher quality fiber networks. Trading-off the different static and dynamic goals, the paper provides guidelines and suggestions for policy makers’ decisions

2D PbS Nanosheets Synthesis and Their Applications as Field Effect Transistors or Solar Cells

Two-dimensional, solution-processable semiconductor materials are interesting for low-cost electronic applications [1]. We demonstrate the synthesis of lead sulfide nanosheets and how their size, shape and height can be tuned by varying concentrations of pre-cursors, ligands and by varying the reaction temperature. Especially, the charge carrier confinement in the nanosheets' height adjustable from 2 to 20 nm has a decisive impact on their electronic properties. This is demonstrated by their use as conduction channel in a field effect transistor [2]. Recently we also showed that especially thin nanosheets show a high carrier multiplication (CM) efficiency [3] which could make them, through the confinement induced band gap and high photoconductivity, very attractive for application in photovoltaic devices. We are already able to manufacture photovoltaic devices out of single nanosheets which show promising results

Electron and Spin Transport in the Presence of a Complex Absorbing Potential

We examine the impact of a complex absorbing potential on electron transport both in the continuum and on a lattice. This requires the use of non-Hermitian Hamiltonians; the required formalism is briefly outlined. The lattice formulation allows us to study the interesting problem of an electron interacting with a stationary spin and the subsequent time evolution of the electron and spin properties as the electron is absorbed after the initial interaction. Remarkably, the properties of the localized spin are affected “at a distance” by the interaction of the (now entangled) electron with a complex potential