1,721,203 research outputs found
Laser-cooled atoms and their ionization: perspectives in focused ion beam technologies
No full textSince from their initial introduction, laser-cooling techniques have been proposed as a viable approach to improve the performance of many existing technologies. Recently, a concrete possibility [1] has been outlined in the field of focused ion beams (FIBs), an extremely powerful and versatile nanofabrication method. We demonstrate the potential shown by ionization of laser-cooled atoms [2] in the realization of bright and monochromatic ion beams, targeted to surpass the features of the present FIB machines [3,4].
1. L. Kime et al., Phys. Rev. A 88, 033424 (2013).
2. N. Porfido et al., Phys. Rev. A 92, 043408 (2015).
3. M. Viteau et al., Ultramicroscopy 64, 70 (2016).
4. G. Shayeganrad et al., Phys. Rev. Applied 5, 054020 (2016)
Nanoscopy (and a few optomechanics)
No full textNanoscopy, i.e., the ability to investigate optical properties at the nanoscale, is between the emerging techniques in nanotechnology. In the talk, a survey of recent acrivities related to nanoscopy will be presented, with special emphasis on the use of polarization modulation methods for the analysis of optical acitivity in nanostructures. Connections with optomechanics in nanosized systems will also be outlined
Fluid-driven bacterial accumulation in proximity of laser-textured surfaces
No full textIn this work we investigated the role of fluid in the initial phase of bacterial adhesion on textured surfaces, focusing onto the approach of the bacterial cells towards the surface. In particular, stainless steel surfaces textured via femtosecond laser interaction have been considered. The method combined a simulation routine, based on the numerical solution of Navier-Stokes equations, and the use of a theoretical model, based on the Smoluchowski's equation. Results highlighted a slowdown of the fluid velocity field in correspondence of the surface dales. In addition, a shear induced accumulation on the top of the surface protrusions was predicted for motile bacterial species, E. coli. In particular, we observed a role of the surface protrusions in increasing the range over which motile bacterial species are attracted towards the surface through a rheotactic mechanism. In other words, we found that, in certain conditions of fluid flow and textured surface morphology, surface protrusions act as a sort of "rheotactic antennas"
Pulsed laser deposition of NiTi shape memory effect thin films
No full textWe report for the first time on the pulsed laser deposition of NiTi shape-memory effect thin films. Using a NiTi bulk target with a 1:1 nominal stoichiometry, we deposited thin films (thickness approximate to 0.6 mu m) on both Si(100) and Al2O3(100) substrates. We also produced free-standing NiTi films by deposition on KBr substrates and subsequent substrate removal by immersion in water. The presence of the solid-solid phase transformation responsible for the shape memory effect has been demonstrated through temperature-dependent X-ray diffraction and four-probe resistance versus temperature measurements. On cooling the deposited him, the austenite-martensite transformation was measured at around 195 K; on heating the film the reverse transformation was around 250 K. Evidence of the shape-memory effect for freestanding films was obtained in a bending deformation-shape recovery experiment
EXCITON-POLARITON MODIFICATIONS IN THE PHOTOLUMINESCENCE SPECTRUM OF GAAS MQW
No full textIn the exciton photoluminescence emission from a GaAs MQW sample at room temperature, a strong dependence on the incidence angle of the exciting laser light has been observed. This behaviour is originated by the polariton, i.e. the.exciton coupling to the light. Introducing into a simple rate equation model, the relation between the exciton radiative lifetime broadening and the light wavevector parallel to the MQW plane for a two dimensional system, we have predicted the population of the exciton level and the intensity of exciton emission. The predicted dependence on the incidence angle of the exciting light is in good agreement with the experimental results. This observation is the first experimental confirmation of the radiative polariton lifetime broadening in a MQW, although it represents an indirect evidence through the photoluminescence signal
Laser vaporization of carbon in the presence of carbon dioxide
No full textWe detect, through time-resolved ion mass spectrometry, the production of carbon oxide ions in the laser ablation of graphite in the presence of CO2. The dependence of the ion production on the laser ablation parameters is investigated and the expansion dynamics of the ablated species is studied through time and space resolved measurements of the ion yield. We discuss our observations on the basis of reactions involving neutral and ionized carbon-based species
Integrated porous-silicon light-emitting diodes: a fabrication process using graded doping profiles
No full textA fabrication process, compatible with an industrial bipolar+complementary metal-oxide-semiconductor (MOS)+diffusion MOS technology, has been developed for the fabrication of efficient porous-silicon-based light-emitting diodes. The electrical contact is fabricated with a double n(+)/p doping, achieving a high current injection efficiency and thus lower biasing voltages. The anodization is performed as the last step of the process, thus reducing potential incompatibilities with industrial processes. The fabricated devices show yellow-orange electroluminescence, visible with the naked eye in room lighting. A spectral characterization of light emission is presented and briefly discussed. (C) 2001 American Institute of Physics
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