Investigation of a contacting scheme for self-assembled cleaved edge overgrown InAs nanowires and quantum dot arrays

A contacting scheme to measure the transport properties into self-assembled InAs Quantum Wires (QWRs) or Quantum Dots (QDs) is presented. The nanostructures are formed on the (110) cleaved edge of a AlAs/AlGaAs heterostructure substrate by means of the Cleaved Edge Overgrowth (CEO) technique and Molecular Beam Epitaxy (MBE). The InAs nanostructure grows directly on top of the AlAs layer, which hosts a two dimensional electron gas (2DEG). In a transistor-like schematic of the device, the 2DEG acts as a contact to the InAs nanostructure. A top gate is used to deplete the 2DEG, thereby defining the InAs nanostructure as a channel L between source and drain. Measurements confirm that the device can be operated as a field-effect transistor, but no evidence of a current flow through the InAs QWRs can be found. Numerical calculations of the electron density and the device band structure confirm that a depletion zone is present in the AlAs layer close to the cleaved edge and the InAs QWR seems electrically isolated from the AlAs 2DEG leads. Possible solutions could be an additional Schottky gate contact on the CEO side or selective doping inside the CEO barrier. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Collins and Sivers asymmetries in muonproduction of pions and kaons off transversely polarised protons

Measurements of the Collins and Sivers asymmetries for charged pions and charged and neutral kaons produced in semi-inclusive deep-inelastic scattering of high energy muons off transversely polarised protons are presented. The results were obtained using all the available COMPASS proton data, which were taken in the years 2007 and 2010. The Collins asymmetries exhibit in the valence region a non-zero signal for pions and there are hints of non-zero signal also for kaons. The Sivers asymmetries are found to be positive for positive pions and kaons and compatible with zero otherwise. © 2015

Piezoelectric, dielectric and pyroelectric properties of 0-3 ceramic-polymer composites

The circular samples of composites were made from PZT ceramic grains dispersed in polymers (epoxy or rubber). Pressure dependencies of the hydrostatic piezoelectric coefficient dh and permittivity ε were measured in the range up to 60 MPa. The hydrostatic strain coefficient dh, the hydrostatic voltage coefficient gh and figure of merit dh·gh were determined using the static method. The pressure dependence of the hydrostatic coefficients was measured for several successive cycles. Experimental dependence of the charge on pressure and temperature was fitted by multi parameter function. The pressure and temperature dependencies of the hydrostatic dh and pyroelectric p3 coefficients were determined. It was found that the hydrostatic strain coefficient dh and hydrostatic voltage coefficient gh decreased and pyroelectric coefficient p3 increased with pressure at constant temperature.DFG [1102]; ICTP programme for Training and Research in Italian Laboratories (TRIL); German Bundesministerium fur Bildung und Forschung; Czech Republic MEYS Grants [ME492, LA242]; SAIL (CSR), Govt. of India; CERN-RFBR Grants [08-02-91009, 12-02-91500]; Portuguese FCT - Fundacao para a Ciencia e Tecnologia [CERN/FP/109323/2009, CERN/FP/116376/2010, CERN/FP/123600/2011]; MEXT; JSPS [18002006, 20540299, 18540281]; Daiko Foundation; Yamada Foundation; DFG cluster of excellence 'Origin and Structure of the Universe'; EU FP7 (HadronPhysics3) [283286]; Israel Science Foundation; Polish NCN Grant [DEC-2011/01/M/ST2/02350