Search results for "electronics"
showing 10 items of 4340 documents
Optical properties of thin metal films with nanohole arrays on porous alumina–aluminum structures
2015
A multilayer system is formed by the deposition of a 10–35 nm thin Au or Ag film with 18–25 nm diameter holes on 75–280 nm thick layers of porous anodized aluminum oxide (AAO) supported by a bulk sheet of aluminum. We present a detailed study of system parameters, which influence the optical response, including the porosity, metal layer thickness and crystallographic orientation of the Al substrate. The spectral properties are mainly governed by the interference of the reflections from the Al substrate and the thin metal film separated by the AAO layer. An enhanced plasmonic attenuation component near 650 nm for the Au films with holes can be observed when the interferometric anti-reflectio…
Electrochemically prepared oxides for resistive switching memories
2018
Redox-based resistive switching memories (ReRAMs) are the strongest candidates for next generation nonvolatile memories. These devices are commonly composed of metal/solid electrolyte/metal junctions, where the solid electrolyte is usually an oxide layer. A key aspect in the ReRAMs development is the solid electrolyte engineering, since it is crucial to tailor the material properties for obtaining excellent switching properties (e.g. retention, endurance, etc.). Here we present an anodizing process as a non vacuum and low temperature electrochemical technique for growing oxides with tailored structural and electronic properties. The effect of the anodizing conditions on the solid state prop…
Near-Field Distribution of Optical Transmission of Periodic Subwavelength Holes in a Metal Film
2000
Recent experimental discovery of the enhanced optical transmission through metal films with periodic subwavelength holes has given rise to a considerable interest in the optical properties of such structures due to their possible numerous applications in optics and optoelectronics as well as rich physics behind the phenomenon of the transmission enhancement [1–4]. The transmission of a subwavelength aperture is very low and proportional to the fourth power of the ratio of its diameter and light wavelength. However, if a metal film is perforated with a periodic array of such holes, the optical transmission can be significantly enhanced [1]. Being normalized to the total area of the illuminat…
Tunable Wide‐Bandgap Monohalide Perovskites
2020
Herein the mechanochemical synthesis of inorganic as well as hybrid organic-inorganic monohalide perovskites with tunable bandgaps is reported. It is shown that the bandgap bowing known for iodide mixed Sn-Pb perovskites is also present in the pure bromide analogous. This results in technologically very interesting materials with bandgaps in the range of 1.7-1.9 eV. Similar bandgap perovskites are typically achieved by mixing two halides that are prone to segregate over time. This limits the achievable open circuit voltage. For monohalide perovskites this problem is eliminated, making these materials especially promising wide bandgap absorbers for tandem solar cells. Perovskite Thin-film Ph…
Comparativeab initiostudy of half-Heusler compounds for optoelectronic applications
2010
For the advancement of optoelectronic applications, such as thin-film solar cells or laser diodes, there is a strong demand for new semiconductor materials with tailored structural and electronic properties. The eight-electron half-Heusler compounds include many promising materials with a big variety of lattice constants and band gaps. So far only a small number of them have been investigated. With the help of ab initio calculations, we have studied all possible configurations of ternary 1:1:1 compounds in the half-Heusler structure. We have investigated 648 half-Heusler materials, including compounds of the types I-I-VI, I-II-V, I-III-IV, II-II-IV, and II-III-III. For all compounds, we hav…
Energy structure and electro-optical properties of organic layers with carbazole derivative
2014
Abstract Phosphorescent organic light emitting diodes are perspective in lighting technologies due to high efficient electroluminescence. Not only phosphorescent dyes but also host materials are important aspect to be considered in the devices where they are a problem for blue light emitting phosphorescent molecules. Carbazole derivative 3,6-di(9-carbazolyl)-9-(2-ethylhexyl)carbazole (TCz1) is a good candidate and has shown excellent results in thermally evaporated films. This paper presents the studies of electrical properties and energy structure in thin films of spin-coated TCz1 and thermally evaporated tris[2-(2,4-difluorophenyl)pyridine]iridium(III) (Ir(Fppy)3). The 0.46 eV difference …
I-II-V half-Heusler compounds for optoelectronics:Ab initiocalculations
2010
Half-Heusler compounds $XYZ$ crystallize in the space group $F\overline{4}3m$ and can be viewed as a zinc-blende-like ${(YZ)}^{\ensuremath{-}}$ lattice partially filled with He-like ${X}^{+}$ interstitials. In this work, we investigated I-II-V (eight-electrons) half-Heusler compounds by first-principles calculations in order to find suitable semiconductors for optoelectronics such as Cd-free buffer layer materials for chalcopyrite-based thin-film solar-cell devices. We report a systematic examination of band gaps and lattice parameters, depending on the electronegativities and the ion radii of the involved elements. Half-Heusler buffer materials should have a band gap of more than 2 eV to a…
Negative capacitance caused by electron injection through interfacial states in organic light-emitting diodes
2006
The negative capacitance frequently observed at low frequencies in organic light-emitting diodes (LEDs) is explained as a signature of sequential electron injection at the organic/metal interface first to states in the bandgap in the dipole layer and then to bulk states. The negative capacitance occurs when the interfacial states depart from equilibrium with the metal Fermi level due to an increasing rate of hopping to the bulk states. A simple kinetic model compares well with the experimental results and provides a new tool to investigate interfacial properties for improving the performance of organic LEDs.
High-Speed Memory from Carbon Nanotube Field-Effect Transistors with High-κ Gate Dielectric
2009
We demonstrate 100 ns write/erase speed of single-walled carbon nanotube field-effect transistor (SWCNT-FET) memory elements. With this high operation speed, SWCNT-FET memory elements can compete with state of the art commercial Flash memories in this figure of merit. The endurance of the memory elements is shown to exceed 104 cycles. The SWCNT-FETs have atomic layer deposited hafnium oxide as a gate dielectric, and the devices are passivated by another hafnium oxide layer in order to reduce surface chemistry effects. We discuss a model where the hafnium oxide has defect states situated above, but close in energy to, the band gap of the SWCNT. The fast and efficient charging and discharging…
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).