We report on current-induced domain wall motion (CIDWM) in Ta\Co

Abstract-Electroencephalograph

A model to compute the strain relaxation rate in InxGa1−xAs/GaAs single layers has been tested on several compositionally graded buffer layers. The existence of a critical elastic energy has been assumed as a criterion for the generation of new misfit dislocations. The surface strain accuracy results are within 2.5×10−4. The influence of different grading laws and growth conditions on residual strain, threading dislocation density, misfit dislocation confinement, and surface morphology has been studied. The probability of dislocation interaction and work hardening has been shown to strongly influence the mobility and the generation rate of the dislocations. Optimization of the growth conditions removes residual strain asymmetries and smoothes the surface roughness.

The structural defects in two-dimensional transition metal dichalcogenides, including point defects, dislocations and grain boundaries, are scarcely considered regarding their potential to manipulate the electrical and optical properties of this class of materials, notwithstanding the significant advances already made. Indeed, impurities and vacancies may influence the exciton population, create disorder-induced localization, as well as modify the electrical behaviour of the material. Here we report on the experimental evidence, confirmed by ab initio calculations, that sulfur vacancies give rise to a novel near-infrared emission peak around 0.75 eV in exfoliated MoS2 flakes. In addition, we demonstrate an excess of sulfur vacancies at the flake's edges by means of cathodoluminescence mapping, aberration-corrected transmission electron microscopy imaging and electron energy loss analyses. Moreover, we show that ripplocations, extended line defects peculiar to this material, broaden and redshift the MoS2 indirect bandgap emission.

In this paper, we present a systematic study of the effect of growth parameters on the structural and optical properties of InAs quantum dot ͑QD͒ grown under Stranski-Krastanov mode by molecular beam epitaxy. The dot density is significantly reduced from 1.9ϫ10 10 to 0.6ϫ10 10 cm Ϫ2 as the growth rate decreases from 0.075 to 0.019 ML/s, while the island size becomes larger. Correspondingly, the emission wavelength shifts to the longer side. By increasing the indium fraction in the InGaAs capping layer, the emission wavelength increases further. At indium fraction of 0.3, a ground state transition wavelength as long as 1.4 m with the excited state transition wavelength of around 1.3 m has been achieved in our dots. The optical properties of QDs with a ground state transition wavelength of 1.3 m but with different growth techniques were compared. The QDs grown with higher rate and embedded by InGaAs have a higher intensity saturation level from excitation dependent photoluminescence measurements and a smaller intensity decrease from temperature dependent measurements. Finally, single mirror light emitting diodes with a QD embedded in InGaAs have been fabricated. The quantum efficiency at room temperature is 1.3%, corresponding to a radiative efficiency of 21.5%.

Highly oriented antimony telluride thin films are prepared by room temperature metalorganic chemical vapor deposition on Si(111).

Tailoring the structural and electronic properties of 3D nanostructures via bottom-up techniques would pave the way for novel low-cost applications. One of such possibilities is offered by ZnO branched nanostructures like tetrapods, that have recently attracted attention for nanodevice applications from nanoelectronics to drug delivery. The conventional picture is that ZnO arms are thermodynamically stable only in the wurtzite phase. Here, we provide the first experimental evidence of unpredicted extended zinc blend phases (50-60 nm long) embedded in the arms of ZnO wurtzite tetrapods. In particular, decisive evidence is obtained from the one-to-one correlation between high lateral resolution cathodoluminescence spectroscopy, monochromatic contrast maps, and atomic resolution transmission electron microscopy images of ZnO single TPs. This observation is not specific to ZnO and can have a general validity for the understanding of the nucleation mechanisms in semiconducting 3D nanostructures for device applications.

In the present work the optical properties of In2O3 nanowires, grown by the vapour transport process, have been investigated by means of photo- (PL) and cathodo-luminescence (CL), applied in the ultraviolet (UV)–visible range. Although In2O3 is expected not to emit light at room temperature, a complex photo-luminescence emission spectrum has been revealed and its temperature dependence has been carefully analysed by varying the temperature from 20 to 300 K. The influence of the substrate on the photo-luminescence spectra has been studied by performing low-temperature measurements on In2O3 nanowires deposited both on alumina and silicon substrates. Some samples have been submitted to suitable thermal treatments (in oxygen-rich atmosphere at 1000 °C), whose effects on the In2O3 nanowires’ emission have been put in evidence. When performed with low magnification, cathodo-luminescence has revealed the same features as photo-luminescence spectroscopy. When applied with high magnification, cathodo-luminescence can provide the emission spectra of a single nanostructure. The CL spectra have been measured for the first time on a single In2O3 nanowire, before and after in situ electron-beam irradiation. Thanks to this comparative analysis, the effectiveness of the growth procedure in obtaining good-quality materials has been demonstrated and the unexpected bands exhibited by In2O3 nanowires have been tentatively attributed to specific defects. In particular, an orange emission, whose amplitude can be increased by submitting the sample to appropriate thermal treatments, has been revealed (both with PL and CL spectroscopy) and might be exploited for visible laser applications.