The methods to detect vacuum polarization by evanescent modes

We propose the evanescent-mode-sensing methods to probe the electrodynamics (QED) vacuum polarization. From our methods, high-sensitivity can be achieved even though the external field is much smaller than the Schwinger critical field and may be realizable in contemporary experimental conditions. The methods are based on the effect of phase change and time delay of evanescent wave which is transmitted in QED vacuum. These methods can also be widely used in sensitive probing of tiny dissipation in other fields

Swift heavy ions effects in III–V nitrides

Four III–V nitrides, BN, AlN, GaN and InN have been irradiated under normal incidence at 300 K at GANIL (Caen, France) accelerator with 132 MeV 209Pb32+ swift heavy ions. Specimens were ion thinned for TEM observations before irradiation. Boron and aluminium nitrides were undamaged by the irradiation unlike the two others. In gallium and indium nitrides, ion impacts are found, forming circular areas. Their diameters are 3 and 8 nm, respectively. In fact, two regions may be distinguished around the ion impact: the inner part attributed to the section of the track formed along the ion path and corresponding to re-crystallized material and the external part to a strained material. For InN, structural defects, dislocations or interstitial loops are localised at the interface between the two regions and in the inner part

Screw threading dislocations in AlN: Structural and electronic properties of In and O doped material

Density functional theory calculations were performed on undoped AlN screw threading dislocations (TDs) as well as TDs doped by indium and oxygen, prompted by integrated experiments through transmission electron microscopy and spectroscopic techniques demonstrating enhanced In and O concentrations in screw dislocation cores. It is revealed that screw TDs act as conduction pathways to charge carriers, introducing multiple levels in the bandgap due to overstrained, dangling, and “wrong” bonds formed even in the undoped cores. The presence of impurities and especially metallic In elevates the metal-like electronic structure of the distorted material and promotes the conductivity along the dislocation line. Hence screw dislocations in AlN are established as highly prominent conductive nanowires in semiconducting thin films and prospects for novel, highly functional nano-device materials through exploitation of screw TDs are attested

Study of flash evaporated Culn1-x GaxTe2 (x=0, 0.5 and 1) thin films

International audienceCuIn1 − xGaxTe2 thin films with x=0, 0.5 and 1, have been prepared by flash evaporation technique. These semiconducting layers present a chalcopyrite structure. The optical measurements have been carried out in the wavelength range 200–3000 nm. The linear dependence of the lattice parameters as a function of Ga content obeying Vegard's law was observed. The films have high absorption coefficients (4•104 cm−1) and optical band gaps ranging from 1.06 eV for CuInTe2 to 1.21 eV for CuGaTe2. The fundamental transition energies of the CuIn1−xGaxTe2 thin films can be fitted by a parabolic equation namely Eg1(x)=1.06+0.237x−0.082x2. The second transition energies of the CuInTe2 and CuGaTe2 films were estimated to be: Eg2=1.21 eV and Eg2=1.39 eV respectively. This variation of the energy gap with x has allowed the achievement of absorber layers with large gaps