Unusual nanostructures of "lattice matched" InP on AlInAs

We show that the morphology of the initial monolayers of InP on Al0.48In0.52As grown by metalorganic vapor-phase epitaxy does not follow the expected layer-by-layer growth mode of lattice-matched systems, but instead develops a number of low-dimensional structures, e.g., quantum dots and wires. We discuss how the macroscopically strain-free heteroepitaxy might be strongly affected by local phase separation/alloying-induced strain and that the preferred aggregation of adatom species on the substrate surface and reduced wettability of InP on AlInAs surfaces might be the cause of the unusual (step) organization and morpholog

Impact of Nitrogen incorporation on pseudomorphic site-controlled quantum dots grown by Metalorganic Vapour Phase Epitaxy

We report on some surprising optical properties of diluted nitride InGaAs_(1-y)N_y /GaAs (y<<1) pyramidal site-controlled quantum dots, grown by metalorganic vapor phase epitaxy on patterned GaAs (111)B substrates. Microphotoluminescence characterizations showed antibinding exciton/ biexciton behavior, a spread of exciton lifetimes in an otherwise very uniform sample, with unexpected long neutral exciton lifetimes (up to 7 ns) and a nearly zero fine structure splitting on a majority of dots

Wettability and "petal effect" of GaAs native oxides

We discuss unreported transitions of oxidized GaAs surfaces between (super)hydrophilic and hydrophobic states when stored in ambient conditions. Contact angles higher than 90deg and high adhesive force were observed for several air-aged epitaxial samples grown under different conditions as well as on epi-ready wafers. Regardless of the morphologies of the surface, superhydrophilicity of oxygen-plasma treated samples was observed, an effect disappearing with storage time. Reproducible hydrophobicity was likewise observed, as expected, after standard HCl surface etching. The relation between surface oxides and hydrophobic/hydrophilic behavior is discussed

Conditions for entangled photon emission from (111)B site-controlled Pyramidal quantum dots

A study of highly symmetric site-controlled Pyramidal In0.25Ga0.75As quantum dots (QDs) is presented. It is discussed that polarization-entangled photons can be also obtained from Pyramidal QDs of different designs from the one already reported in Juska et al. (Nat. Phot. 7, 527, 2013). Moreover, some of the limitations for a higher density of entangled photon emitters are addressed. Among these issues are (1) a remaining small fine-structure splitting and (2) an effective QD charging under non-resonant excitation conditions, which strongly reduce the number of useful biexciton-exciton recombination events. A possible solution of the charging problem is investigated exploiting a dual-wavelength excitation technique, which allows a gradual QD charge tuning from strongly negative to positive and, eventually, efficient detection of entangled photons from QDs, which would be otherwise ineffective under a single-wavelength (non-resonant) excitation

The Influence of E - Stim on Posture and Respiratory Function to Improve Aerobic Capacity: A Pilot

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Semiconductor nanostructures engineering: Pyramidal quantum dots

Pyramidal quantum dots (QDs) grown in inverted recesses have demonstrated over the years an extraordinary uniformity, high spectral purity and strong design versatility. We discuss recent results, also in view of the Stranski-Krastanow competition and give evidence for strong perspectives in quantum information applications for this system. We examine the possibility of generating entangled and indistinguishable photons, together with the need for the implementation of a, regrettably still missing, strategy for electrical control

Conflict and Astroturfing in Niyamgiri: The Importance of National Advocacy Networks in Anti-Corporate Social Movements

Traditional models of transnational advocacy networks (TANs) and stakeholder management do not capture the nuance and dynamics of (counter-)organising processes around anti-corporate mobilisation. Based on the case of a resistance movement against a planned bauxite mine on tribal land in India, we develop a process theory of interactions between local, national and international actors within transnational advocacy networks. These encounters are not always friendly and are often characterised by conflict between actors with disparate goals and interests. We highlight the importance of national advocacy networks (NANs) in anti-corporate social movements and describe the conflicts and disruptions that result from ignoring them. Our findings also point to the role of corporate counter-mobilisation strategies in shaping resistance movements. Our narrative revolves around a particular focal actor in the anti-mining campaign: a young tribal man who emerged as a passionate spokesperson of the movement, but later became a supporter of the controversial mine. Our findings contribute to a richer understanding of the processes underlying transnational and national anti-corporate mobilisation