Search results for "COPI"
showing 10 items of 2618 documents
Phonon Softening and Electron-Phonon Interaction in YBa2Cu3O7−δ
1993
We report on the Raman scattering investigation of the 335 cm−1 phonon of Ag (pseudo-B1g) symmetry in thin YBa2Cu3O7−δfilms on various substrates. The experiments yield values for the phonon softening below Tc, which differ from sample to sample. We find a linear relation between the softening and the inverse asymmetry parameter of the phonon Fano-like lineshape, when these parameters, obtained from different samples, are compared with each other. In contrast to this, the onset temperatures for the softening are the same for these samples.
Design and operation of CMOS-compatible electron pumps fabricated with optical lithography
2017
We report CMOS-compatible quantized current sources (electron pumps) fabricated with nanowires (NWs) on 300mm SOI wafers. Unlike other Al, GaAs or Si based metallic or semiconductor pumps, the fabrication does not rely on electron-beam lithography. The structure consists of two gates in series on the nanowire and the only difference with the SOI nanowire process lies in long (40nm) nitride spacers. As a result a single, silicide island gets isolated between the gates and transport is dominated by Coulomb blockade at cryogenic temperatures thanks to the small size and therefore capacitance of this island. Operation and performances comparable to devices fabricated using e-beam lithography is…
Origin of the substrate current after soft-breakdown in thin oxide n-MOSFETs
1999
In this paper is presented an experimental investigation on the origin of the substrate current after soft-breakdown in n-MOSFETs with 4.5 nm-thick oxide. At lower voltages this current shows a plateau that can be explained with the generation of hole-electron pairs in the space charge region and at the Si-SiO2 interface, and to carrier diffusion between the channel and the substrate. At higher voltages the substrate current steeply increases with voltage, due to trap-assisted tunneling from the substrate valence band to the gate conduction band, which becomes possible for gate voltages higher than the threshold voltage. Measurements on several devices at dark and in the presence of light, …
The effect of band gap alignment on the hole transport from semiconducting block copolymers to quantum dots
2013
Semiconducting hole transporting block copolymers were chemically modified to adjust their energy levels to that of CdSe/CdS/CdZnS red quantum dots. Hybrids with optimized energy levels could be used to build strongly improved quantum dot based LEDs (QLEDs).
Quantifiable analysis of the failure of advanced carbon fibre composite structures leading to improved safety factors
2022
Abstract The increasing use of advanced composite materials means that they must now be considered as major materials for a wide variety of structures some of which will be in service for decades. There is therefore an important need to be able to quantify damage accumulation leading to failure in these materials particularly as they are often used in extreme situations for which failure must be avoided. This review shows how damage accumulation in many major composite structures is dominated by fibre failure but that the viscoelastic nature of the matrix induces time effects including delayed failure. It is shown that damage accumulation can be quantitatively modelled using a multi-scale a…
Computer modelling of WGM microresonators with a zinc oxide nanolayer using COMSOL multiphysics software
2021
Whispering gallery mode resonators (WGMRs) are small axial symmetrical structures from transparent material, that can exceptionally well confine light within, thus making them ideal for studying light-matter interactions and using them as sensors. Various WGMR designs can be simulated using COMSOL Multiphysics. Sometimes an extra layer is coated on the surface of the resonator for achieving desirable effects. The extra layer changes quality factor of the resonator and ads extra modes for some frequencies. Different methods and studies are used for the exploration of this topic such as changing the thickness of the coating and using random functions to describe the roughness of the surface, …
Surface plasmon polaritons in metal stripes and wires
2004
Surface plasmon polaritons (SPPs) are collective electron oscillations coupled to a light field which are propagating along the interface of a metal and a dielectric. As a surface wave, SPP modes feature properties essentially different from light-field modes in all dielectric structures. These properties could allow the realization of novel photonic devices that overcome certain limitations of conventional devices. Specifically, the realization of two-dimensional optics and light-field transport in sub-wavelength SPP waveguides seems feasible. In this review we discuss recent experimental advances regarding SPP waveguides, i.e. laterally confined metal thin films that guide SPPs. Electron-…
Direct observation of localized surface plasmon coupling
1999
We report on the direct observation of localized surface plasmon coupling using a photon scanning tunneling microscope. The surface plasmons are excited in gold nanostructures tailored by electron beam lithography. Electromagnetic energy transfer from a resonantly excited nanoparticle to a nanowire, which is not directly excited by the incident light is observed. Our experimental results appear to be in good agreement with theoretical computations based on Green's dyadic technique.
Controlling Light Confinement by Excitation of Localized Surface Plasmons
2007
Localized surface plasmons can be used to control near-field optical phenomena in the subwavelength range. Specifically, this chaper reviews recent results which show that localized surface plasmons can confine the optical intensity down to nanoscopic dimensions. The discussion first considers how a collection-mode near-field optical microscope can observe the squeezing of the plasmon field of metallic nanostructures deposited on a flat surface. Numerical simulations then provide illustrations of the confined fields associated with nanostructures which are feasible using current microfabrication techniques. Finally, we present arguments which explain how localized surface plasmons can deliv…
Three dimensional nanoscale analysis reveals aperiodic mesopores in a covalent organic framework and conjugated microporous polymer.
2019
The integrated analytical approach developed in this study offers a powerful methodology for the structural characterisation of complex molecular nanomaterials. Structures of a covalent organic framework based on boronate esters (COF-5) and a conjugated microporous polymer (Aza-CMP) have been investigated by a combination of several electron microscopy techniques elucidating the three-dimensional topology of the complex polycrystalline (COF) and non-crystalline (CMP) materials. Unexpected, aperiodic mesoporous channels of 20-50 nm in diameter were found to be penetrating the COF and CMP particles, which cannot be detected by X-ray diffraction techniques. The mesopores appear to be stable un…