Quantum dots (QDs) are being highlighted in display applications for their excellent optical properties, including tunable bandgaps, narrow emission bandwidth, and high efficiency. However, issues ...with their stability must be overcome to achieve the next level of development. QDs are utilized in display applications for their photoluminescence (PL) and electroluminescence. The PL characteristics of QDs are applied to display or lighting applications in the form of color‐conversion QD films, and the electroluminescence of QDs is utilized in quantum dot light‐emitting diodes (QLEDs). Studies on the stability of QDs and QD devices in display applications are reviewed herein. QDs can be degraded by oxygen, water, thermal heating, and UV exposure. Various approaches have been developed to protect QDs from degradation by controlling the composition of their shells and ligands. Phosphorescent QDs have been protected by bulky ligands, physical incorporation in polymer matrices, and covalent bonding with polymer matrices. The stability of electroluminescent QLEDs can be enhanced by using inorganic charge transport layers and by improving charge balance. As understanding of the degradation mechanisms of QDs increases and more stable QDs and display devices are developed, QDs are expected to play critical roles in advanced display applications.
Technologies to enhance the stability of quantum dots (QDs), quantum dot films, and quantum dot light‐emitting diodes for display applications are summarized and suggested. Degradation mechanisms of QDs are discussed in aspects of water, oxygen, and thermal energy. Various technologies to maintain the quantum yield of QDs, the photoluminescence intensity of QD films, and the lifetime of quantum dot light‐emitting diodes are discussed.
High harmonic generation of ultrafast laser pulses can be used to perform angle-resolved photoemission spectroscopy (ARPES) to map the electronic band structure of materials with femtosecond time ...resolution. However, currently it is difficult to reach high momenta with narrow energy resolution. Here, we combine a gas phase extreme ultraviolet (XUV) femtosecond light source, an XUV monochromator, and a time-of-flight electron analyzer to develop XUV-based time-resolved ARPES. Our technique can produce tunable photon energy between 24-33 eV with an unprecedented energy resolution of 30 meV and time resolution of 200 fs. This technique enables time-, energy- and momentum-resolved investigation of the nonequilibrium dynamics of electrons in materials with a full access to their first Brillouin zone. We evaluate the performance of this setup through exemplary measurements on various quantum materials, including WTe
, WSe
, TiSe
, and Bi
Sr
CaCu
O
.
Molecular MIMO: From Theory to Prototype Bon-Hong Koo; Changmin Lee; Yilmaz, H. Birkan ...
IEEE journal on selected areas in communications,
03/2016, Letnik:
34, Številka:
3
Journal Article
Recenzirano
Odprti dostop
In diffusion-based molecular communication, information transport is governed by diffusion through a fluid medium. The achievable data rates for these channels are very low compared to the ...radio-based communication system, since diffusion can be a slow process. To improve the data rate, a novel multiple-input multiple-output (MIMO) design for molecular communication is proposed that utilizes multiple molecular emitters at the transmitter and multiple molecular detectors at the receiver (in RF communication these all correspond to antennas). Using particle-based simulators, the channel's impulse response is obtained and mathematically modeled. These models are then used to determine interlink interference (ILI) and intersymbol interference (ISI). It is assumed that when the receiver has incomplete information regarding the system and the channel state, low complexity symbol detection methods are preferred since the receiver is small and simple. Thus, four detection algorithms are proposed-adaptive thresholding, practical zero forcing with channel models excluding/including the ILI and ISI, and Genie-aided zero forcing. The proposed algorithms are evaluated extensively using numerical and analytical evaluations.
Optoelectronic effects of sidewall passivation on micro-sized light-emitting diodes (µLEDs) using atomic-layer deposition (ALD) were investigated. Moreover, significant enhancements of the optical ...and electrical effects by using ALD were compared with conventional sidewall passivation method, namely plasma-enhanced chemical vapor deposition (PECVD). ALD yielded uniform light emission and the lowest amount of leakage current for all µLED sizes. The importance of sidewall passivation was also demonstrated by comparing leakage current and external quantum efficiency (EQE). The peak EQEs of 20 × 20 µm
µLEDs with ALD sidewall passivation and without sidewall passivation were 33% and 24%, respectively. The results from ALD sidewall passivation revealed that the size-dependent influences on peak EQE can be minimized by proper sidewall treatment.
When a topological insulator (TI) is in contact with a ferromagnet, both time-reversal and inversion symmetries are broken at the interface. An energy gap is formed at the TI surface, and its ...electrons gain a net magnetic moment through short-range exchange interactions. Magnetic TIs can host various exotic quantum phenomena, such as massive Dirac fermions, Majorana fermions, the quantum anomalous Hall effect and chiral edge currents along the domain boundaries. However, selective measurement of induced magnetism at the buried interface has remained a challenge. Using magnetic second-harmonic generation, we directly probe both the in-plane and out-of-plane magnetizations induced at the interface between the ferromagnetic insulator (FMI) EuS and the three-dimensional TI Bi2Se3. Our findings not only allow characterizing magnetism at the TI-FMI interface but also lay the groundwork for imaging magnetic domains and domain boundaries at the magnetic TI surfaces.
Display omitted
•Fate of chlortetracycline (CTC) during anaerobic degradation was investigated.•CTC degradation was explained by the first-order incomplete decay model.•Substantial amounts of epimer- ...CTC, and isomer- CTC was transformed from CTC.•Most of CTC, epimer, and isomer-CTC existed in the solid phase of digestate.•CTC degradation could be inhibited by co-metabolization by substrate.
As veterinary antibiotics (VAs) cause adverse effects on nature, anaerobic digestion (AD) of livestock manure has been receiving attention as an exposure route of VAs. This research evaluated the anaerobic degradation and phase distribution of chlortetracycline (CTC) with its epimer (4-epi-CTC, ECTC) and isomer (Iso-CTC, ICTC). In addition, whether CTC can inhibit not only AD of a substrate but also the degradation of CTC was assessed. Anaerobic batch assays were performed with cattle manure for 30 days by varying the initial concentration of CTC; 0, 10, 25, 50, and 100 mg/L. Approximately 25–43 % (w/w) of CTC was primarily degraded while 18–25 % and 20–26 % of CTC was transformed into ECTC and ICTC, respectively. Up to 88 % (w/w) of the remaining CTC, ECTC, and ICTC was present in the solid phase. In addition, CTC inhibited not only the mineralization of the cattle manure but also the degradation of CTC due to co-metabolism. In conclusion, significant quantities of CTC, ECTC, and ICTC can be exposed to nature by solid phase of anaerobic digestate. The inhibition on AD can reduce the degradation of CTC, ECTC, and ICTC during the AD.
A systematic modulation of the carrier type in molybdenum ditelluride (MoTe2) field‐effect transistors (FETs) is described, through rapid thermal annealing (RTA) under a controlled O2 environment ...(p‐type modulation) and benzyl viologen (BV) doping (n‐type modulation). Al2O3 capping is then introduced to improve the carrier mobilities and device stability. MoTe2 is found to be ultrasensitive to O2 at elevated temperatures (250 °C). Charge carriers of MoTe2 flakes annealed via RTA at various vacuum levels are tuned between predominantly pristine n‐type ambipolar, symmetric ambipolar, unipolar p‐type, and degenerate‐like p‐type. Changes in the MoTe2‐transistor performance are confirmed to originate from the physical and chemical absorption and dissociation of O2, especially at tellurium vacancy sites. The electron branch is modulated by varying the BV dopant concentrations and annealing conditions. Unipolar n‐type MoTe2 FETs with a high on–off ratio exceeding 106 are achieved under optimized doping conditions. By introducing Al2O3 capping, carrier field effect mobilities (41 for holes and 80 cm2 V−1 s−1 for electrons) and device stability are improved due to the reduced trap densities and isolation from ambient air. Lateral MoTe2 p–n diodes with an ideality factor of 1.2 are fabricated using the p‐ and n‐type doping technique to test the superb potential of the doping method in functional electronic device applications.
Unipolar p‐ and n‐type molybdenum ditelluride (MoTe2) field‐effect transistors are achieved through controllable doping techniques. With Al2O3 capping, hole and electron mobility are improved to 41 and 80 cm2 V−1s−1, respectively. Lateral MoTe2 p–n diodes with an ideality factor of 1.2 are fabricated by combining the p‐ and n‐type doping techniques.
Symmetry-breaking charge transfer (SBCT) is an important process at the early stages of the photoinduced processes in multichromophore systems such as the photosynthetic apparatus. We investigated ...the photoinduced SBCT dynamics of 9,9'-bianthracene (BA), a representative molecule showing SBCT, by time-resolved fluorescence (TF) with the highest time-resolution and excited-state quantum mechanics/effective fragment potential molecular dynamics (MD) simulation. TF experiments show that the SBCT kinetics matches quantitatively with the solvation function excluding the initial ultrafast component that is assigned to the inertial motion of the solvent. Therefore, it is established that the SBCT of BA is coupled solely with the rotational diffusion of solvent molecules excluding the inertial motion of solvents. MD simulations show that random rotational fluctuation of solvents mostly in the first solvation shell generates a transient electric field as high as 1.0 × 109 V m-1, which provides an asymmetric environment required for the generation of a CT state in this symmetric dimer. Once the CT state is formed, the dipole moment in the solute causes further rotation of solvent molecules leading to an augmented electric field, which in turn further stabilizes the CT state prohibiting the reverse reaction.
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