Search results for "electronics"

Unexpected Epitaxial Growth of a Few WS2 Layers on {11̅00} Facets of ZnO Nanowires

2016

Core–shell nanowires are an interesting and perspective class of radially heterostructured nanomaterials where epitaxial growth of the shell can be realized even at noticeable core–shell lattice mismatch. In this study epitaxial hexagonally shaped shell consisting of WS2 nanolayers was grown on {1100} facets of prismatic wurtzite-structured [0001]-oriented ZnO nanowires for the first time. A synthesis was performed by annealing in a sulfur atmosphere of ZnO/WO3 core–shell structures, produced by reactive dc magnetron sputtering of an amorphous a-WO3 layer on top of ZnO nanowire array. The morphology and phase composition of synthesized ZnO/WS2 core–shell nanowires were confirmed by scanning…

Role of Self-Absorption in the Photoluminescence Waveguided along CsPbBr3 Perovskite Nanocrystals Thin Films

2020

During the last years, perovskite nanocrystals (PNCs) have been intensively studied as nanomaterials with excellent light absorption/emission properties. For example, PNCs have been successfully applied in solar cells, where the high absorption coefficient above the band gap increases the conversion efficiencies; or in optical sources, where the high quantum yield of emission at room temperature allows a low threshold of stimulated emission. In this scenario, an optical waveguide represents a suitable platform to enhance their electrooptical properties and to integrate different photonic functionalities. However, propagation of light along close packed films of PNCs is usually restricted to…

Origin of enhanced efficiency and stability in diblock copolymer-grafted Cd-free quantum dot-based light-emitting diodes

2021

The efficiency and operational lifetime of quantum dot (QD) based light-emitting diodes (QLEDs) are essentially affected by the electron–hole charge balance. Although various methods have been reported to improve the charge balance, these methods cause issues at the same time, such as increasing a driving voltage and complicating a device structure. In this work, we introduce hybrid InP/ZnSeS/ZnS QDs, in which the oleic acid ligands are substituted with semiconducting diblock copolymer units possessing hole-transporting carbazole groups, to facilitate hole injection and to reduce electron leakage. As a result, the efficiency and the operational lifetime were improved by 1.4-fold and 4-fold,…

Time-resolved cathodoluminescence and photoluminescence of nanoscale oxides

2009

The nanostructured oxide materials such as ZnO, ZrO2, and Y3Al5O12 (YAG) are perspective materials for transparent scintillating and/or laser ceramics. The luminescence properties of single crystals, nanopowders and ceramic were compared. Nominally pure and rare-earth doped nanopowders and ceramics have been studied by means of time-resolved luminescence spectroscopy. The fast blue luminescence band was studied in ZnO ceramics sintering from different raw materials. The luminescence centres of ZrO2:Y were compared in a single crystal, ceramic and nanopowder. It is shown that ceramic sintering parameters have a strong influence on time-resolved luminescence characteristics in cerium-doped YA…

Structural and luminescence properties of GaN nanowires grown using cobalt phthalocyanine as catalyst

2015

Catalyst free methods have usually been employed to avoid any catalyst induced contamination for the synthesis of GaN nanowires with better transport and optical properties. Here, we have used a catalytic route to grow GaN nanowires, which show good optical quality. Structural and luminescence properties of GaN nanowires grown by vapor-liquid-solid technique using cobalt phthalocyanine as catalyst are systematically investigated as a function of various growth parameters such as the growth temperature and III/V ratio. The study reveals that most of the nanowires, which are several tens of microns long, grow along [101¯0] direction. Interestingly, the average wire diameter has been found to …

2015

Two novel charged organic thermally activated delayed fluorescence (TADF) emitters, 1 and 2, have been synthesized. Their TADF behavior is well-supported by the multiexponential decay of their emission (nanosecond and microsecond components) and the oxygen dependence of the photoluminescence quantum yields. Spin-coated electroluminescent devices have been fabricated to make light-emitting electrochemical cells (LEECs) and organic light-emitting diodes (OLEDs). The first example of a non-doped charged small organic molecule LEEC is reported and exhibited an external quantum efficiency (EQE) of 0.39% using 2. With a multilayer architecture, a solution-processed OLED device using neat 2 as the…

Infrared photoluminescence of preexisting or irradiation-induced interstitial oxygen molecules in glassySiO2and α-quartz

1998

A sensitive technique for detecting interstitial ${\mathrm{O}}_{2}$ molecules in ${\mathrm{SiO}}_{2}$ is demonstrated by measuring their infrared $\stackrel{\ensuremath{\rightarrow}}{a}X$ luminescence at 1272.2 nm under a Ti-sapphire laser excitation into the ${\mathrm{O}}_{2}\stackrel{\ensuremath{\rightarrow}}{X}b$ absorption band at 765 nm. Contrary to the case of ${\mathrm{O}}_{2}$ trapped in inert gas matrices, the visible emission of ${\mathrm{O}}_{2}$ corresponding to the direct $\stackrel{\ensuremath{\rightarrow}}{b}X$ transition is not found. Examination of different neutron- and gamma-irradiated glassy ${\mathrm{SiO}}_{2}$ and \ensuremath{\alpha}-quartz samples reveals radiation-in…

Pyroelectric activity of LiGaO2, Li2GeO3, Li2B4O7 and LiNbO3 crystals: Pyroelectric luminescence and excitation of cathodoluminescence in scintillato…

2020

Abstract Basing on results of electric, spectral and kinetic measurements of spontaneous luminescence caused by cooling/heating in pyroelectric crystals LiGaO2, Li2GeO3, Li2B4O7 and LiNbO3 a mechanism of pyroelectric luminescence is proposed. Series of experiments were undertaken attaching a scintillating phosphor ScPO4 to a pyroelectric crystal and subjecting a pair of the bounded crystals to cooling/heating process. Pyroelectric activity causes not only pyroluminescence in pyroelectric crystals but also luminescence in a ScPO4, which is characterized with high intensity and kinetic and spectral properties typical for the intrinsic luminescence of a scintillator.

Growth, structural and optical properties of GaN/AlN and GaN/GaInN nanowire heterostructures

2012

Abstract After discussing the GaN NW nucleation issue, we will present the structural properties of axial and radial (i.e. core/shell) GaN/AlN NW heterostructures and adress the issue of critical thickness during the growth of such heterostructures. Next, we will present the growth of InGaN NWs on a GaN NW base. It will be shown that the morphology and structural properties of the InGaN NW sections depend on the In content: for high In content a flat top is observed and plastic relaxation is occuring, with mismatch dislocations formed at the InGaN/GaN interface. By contrast, for In content below 25% InGaN NWs exhibit a pencil-like shape assigned to a purely elastic strain relaxation process…

Improved Crystalline Structure and Enhanced Photoluminescence of ZnO Nanolayers in Bi2Se3/ZnO Heterostructures

2019

The Bi2Se3/ZnO heterostructure is a new combination of high- and low-band-gap nanomaterials that can be implemented for optoelectronic devices. The influence of the Bi2Se3 substrate on crystallizat...