Search results for "ELECTRONICS"
showing 10 items of 4340 documents
Selective modification of the band gaps of GaInNas/GaAs structures by quantum well intermixing techniques
2003
We report the unambiguous demonstration of controlled quantum well intermixing (QWI) in the technologically important GaInNAs/ GaAs 1.3 mum material system. QWI is a key technique to selectively modify the band gap of quantum wells, which has found broad application in semiconductor lasers and photonic integrated circuits (PICs). Extending such technology to GaInNAs/GaAs structures is highly desirable due to the technologically advantageous properties of this material system. Here, we investigate well-characterized GaInNAs quantum well material which has been annealed "to saturation" before QWI processing to allow unambiguous interpretation of results. After RTA at 700 degreesC for similar …
Performance Comparison of modified modulation Techniques for Quasi-Z-Source Converters
2020
The single-stage converters represent an innovation in the field of power electronics thanks their features. Aim of this work consists in the improvement of the performances of quasi-Z-Source converters by adopting a modified modulation technique, which is based on the Maximum Constant Boost Control (MCBC) and Switching Frequency Optimal (SFO). The results in terms of voltage stress and harmonic content are compared with those obtained with conventional techniques, demonstrating the effectiveness of the proposed modulation scheme.
Extrinsic Effects on the Optical Properties of Surface Color Defects Generated in Hexagonal Boron Nitride Nanosheets
2021
Hexagonal boron nitride (hBN) is a wide-band gap van der Waals material able to host light-emitting centers behaving as single photon sources. Here, we report the generation of color defects in hBN nanosheets dispersed on different kinds of substrates by thermal treatment processes. The optical properties of these defects have been studied using microspectroscopy techniques and far-field simulations of their light emission. Using these techniques, we have found that subsequent ozone treatments of the deposited hBN nanosheets improve the optical emission properties of created defects, as revealed by their zero-phonon linewidth narrowing and reduction of background emission. Microlocalized co…
Exciton quenching by diffusion of 2,3,5,6-tetrafluoro-7,7’,8,8’-tetra cyano quino dimethane and its consequences on joule heating and lifetime of org…
2013
In this Letter, the effect of F(4)-TCNQ insertion at the anode/hole transport layer (HTL) interface was studied on joule heating and the lifetime of organic light-emitting diodes (OLEDs). Joule heating was found to reduce significantly (pixel temperature decrease by about 10 K at a current density of 40 mA/cm(2)) by this insertion. However, the lifetime was found to reduce significantly with a 1 nm thick F(4)-TCNQ layer, and it improved by increasing the thickness of this layer. Thermal diffusion of F(4)-TCNQ into HTL leads to F(4)-TCNQ ionization by charge transfer, and drift of these molecules into the emissive layer caused faster degradation of the OLEDs. This drift was found to reduce w…
Increasing the efficiency of light-emitting electrochemical cells by limiting the exciton quenching
2013
ABSTRACTLight-emitting electrochemical cells (LECs) are one of the simplest electroluminescent devices. The possibility to be processed from solution and to operate with air-stable materials makes them an attractive alternative to organic light emitting diodes (OLEDs). Still their efficiencies are below those obtained in OLEDs. Additionally the best efficiencies were reported at low luminances and sustained for a short period of time. Here we show that for a LEC employing an orange-emitting charged iridium complex that is driven using a pulsed driving scheme high efficiencies of up to 20.5 cd A-1 can be obtained at high luminance and sustained over the device lifetime. It is also shown that…
Luminescence of coesite
2015
Coesite is a polymorph modification of crystalline silicon dioxide with a tetrahedral structure. The luminescence of a single crystal of synthetic coesite was studied under excitation using x-rays, an electron beam, and excimer lasers KrF (248 nm), ArF (193 nm) and F2 (157 nm). Luminescence bands in the regions of 2.5 eV and 4.4 eV appear. The blue band is dependent on temperature and is composed of decay kinetics. Three main decay times are revealed, exhibiting luminescence of a different nature in the same range of the spectrum. One is in the ns range of time with a time constant of about 2 ns. The two other decay times are in the regions of 5 μs and 700 μs. The 5 μs component is also see…
Modeling and Characterization of SiPM Parameters at Temperatures between 95 K and 300 K
2017
The modeling and characterization of silicon photomultipliers (SiPMs) in a wide temperature range from 95 K to 300 K is presented. The devices under study had the distinctive feature of forward-biased p-n junctions situated under each pixel as active quenching resistors making them particularly appropriate to be operated at cryogenic temperatures. The voltage drop across the diode in a forward direction was measured for a series of injected currents in this temperature range. It was observed that the characteristics of different SiPM types influence the temperature dependence of the reverse saturation current. The devices were further characterized by low-level light-pulse measurements. The…
On the operation of silicon photomultipliers at temperatures of 1–4 kelvin
2016
Abstract SiPM operation at cryogenic temperatures fails for many common devices. A particular type from Zecotek with deep channels in the silicon substrate instead of quenching resistors was tested at liquid helium temperature. Two similar types were thoroughly characterized from room temperature down to liquid nitrogen temperature by illuminating them with low light levels. At cryogenic temperatures the SiPMs show an unchanged rise-time and a fast recovery time, practically no after-pulses, and exhibit no increased cross-talk probability. Charge collection spectra were measured to extract the pixel gain and its variation, both comparable to room temperature at the same over-voltage. The qu…
Substrate impact on the thickness dependence of vibrational and optical properties of large area $MoS_2$ produced by gold-assisted exfoliation
2021
The gold-assisted exfoliation is a very effective method to produce large-area ($cm^2$-scale) membranes of molybdenum disulfide ($MoS_2$) for electronics. However, the strong $MoS_2/Au$ interaction, beneficial for the exfoliation process, has a strong impact on the vibrational and light emission properties of $MoS_2$. Here, we report an atomic force microscopy (AFM), micro-Raman ($\mu-R$) and micro-Photoluminescence ($\mu-PL$) investigation of $MoS_2$ with variable thickness exfoliated on Au and subsequently transferred on an $Al_2O_3/Si$ substrate. The $E_{2g}$ - $A_{1g}$ vibrational modes separation $\Delta\mu$ (typically used to estimate $MoS_2$ thickness) exhibits an anomalous large val…
Technical design report for the upgrade of the ALICE inner tracking system
2014
ALICE (A Large Ion Collider Experiment) is studying the physics of strongly interacting matter, and in particular the properties of the Quark–Gluon Plasma (QGP), using proton–proton, proton–nucleus and nucleus–nucleus collisions at the CERN LHC (Large Hadron Collider). The ALICE Collaboration is preparing a major upgrade of the experimental apparatus, planned for installation in the second long LHC shutdown in the years 2018–2019. A key element of the ALICE upgrade is the construction of a new, ultra-light, high- resolution Inner Tracking System (ITS) based on monolithic CMOS pixel detectors. The primary focus of the ITS upgrade is on improving the performance for detection of heavy-flavour…