Search

In this study, the facile synthesis and electroluminescent perovskite light-emitting diodes (PeLEDs) of highly luminescent Cs4PbBr6/CsPbBr3 nanocomposite has been demonstrated. With the addition of...

The amorphous indium gallium oxide thin film transistor was fabricated using a cosputtering method. Two samples with different gate dielectric layers were used as follows: sample A with a SiO2 dielectric layer; and sample B with an Al2O3 dielectric layer. The influence of the gate dielectrics on the electric and photo performance has been investigated. Atomic layer deposition deposited the dense film with low interface trapping density and effectively increased drain current. Therefore, sample B exhibited optimal parameters, with an Ion/Ioff ratio of 7.39 × 107, the subthreshold swing of 0.096 V dec−1, and μFE of 5.36 cm2 V−1 s−1. For ultraviolet (UV) detection, the UV-to-visible rejection ratio of the device was 3 × 105, and the photoresponsivity was 0.38 A W−1 at the VGS of −5 V.

The magnesium oxide is one of the promising candidate's materials that can act as solar blind photodetectors. However, the intrinsically low thermal conductivity of MgO, which is restrict the application in electric device. The magnesium oxide exhibits the poor conductivity which could improved by doing method. This paper fabricated magnesium indium oxide (MgInO) solar-blind photodetectors by doping indium oxide with magnesium oxide through co-sputtering deposition method. The photodetector comprises a bottom glass substrate, an MgInO thin film, and an interdigitated gold electrode to complete the metal-semiconductor-metal structure of the solar-blind photodetector. The experimental results indicate that the photo-to-dark-current ratio is 1.4 × 104, and the responsivity is 1.47 A/W when a reverse bias voltage of 2 V is applied. Furthermore, the noise equivalent power and detectivity are 7.77×10-11 W and 1.75×1011 cm H0.5W-1 with a 2 V bias voltage, respectively.

In this paper, we developed a simple hydrothermal method to synthesize vertically aligned ZnO:Al nanorods (NRs) to fabricate a UV photodetector (PD) on a seed layer/glass substrate. The photo-to-dark current ratio of the ZnO:Al NR PD was approximately $1.4 \times 10^{3}$ under 1-V bias and UV light irradiation (380 nm). The calculated responsivity of the fabricated PD was 181 $\text {A}\cdot \text {W}^{-1}$ , and the UV-to-visible rejection ratio of the PD at 1-V applied bias was $1.51 \times 10^{3}$ . In addition, flicker noise dominated the noise of the ZnO:Al NR PD. The noise-equivalent power and normalized detectivity of the ZnO:Al NR PD were $1.17 \times 10^{-11}$ W and $4.03 \times 10^{12}~\text {cm}\cdot \text {Hz}^{0.5}\text {W}^{-1}$ , respectively.

A novel and simple hydrothermal method was performed to synthesize vertically aligned Ag nanoparticle (NP)-decorated ZnO nanorods (NRs) on a seed layer/glass substrate. At an applied bias of 0.2 V and incident light wavelength of 380 nm, the measured fabricated photodetector (PD) responsivity value was $\sim 12.4$ A/W, whereas the corresponding UV to visible rejection ratio was $\sim 4478$ . In addition, the noise equivalent power and corresponding detectivities of the fabricated Ag NP-decorated ZnO NR metal-semiconductor-metal (MSM) PD were $4.85 \times 10^{\mathrm {-11}}$ W and $2.72 \times 10^{11}~{\mathrm{ cm}}\cdot {\mathrm{ Hz}}^{0.5}\cdot {\mathrm{ W}}^{\mathrm {-1}}$ , respectively.

In this paper, we proposed a novel hybrid quantum dot emitting layer (QD EML) for the efficient quantum dot light-emitting diodes (QLEDs). This proposed hybrid emitting layer consisted of a composite polymer with poly (9-vinlycarbazole) (PVK) and 1,3-bis[(4-tert-butylphenyl)-1,3,4oxadiazolyl]phenylene (OXD-7) in the weight ratio of 7:3 and high quantum yield CdSe@ZnS/ZnS quantum dots. By using PVK as hole transport and OXD-7 as electron transport polymer, both hole and electron was supported to inject into QD efficiently. Consequently, the maximum current efficiencies of 7.9 cd/A was achieved in QLEDs with the hybrid EML, which was $\sim 250$ % improvement over the bared EML-device. Moreover, high color purity and wavelength stable green QLEDs with peak wavelength of 536 nm was also obtained.

In this work, we theoretically investigate the tunable photonic band structure (PBS) for an extrinsic plasma photonic crystal (PPC). The extrinsic PPC is made of a bulk cold plasma layer which is influenced by an externally periodic static magnetic field. The PBS can be tuned by the variation of the magnitude of externally applied magnetic field. In addition, we also show that the PBS can be changed as a function of the electron density as well as the thickness variation.

Vertically aligned Ga-doped ZnO (GZO) nanosheets were grown on a glass substrate using a low-temperature (90 °C) hydrothermal method. The average length and diameter of the nanosheets were \(\sim 720\) and 26 nm, respectively. The GZO nanosheets exhibited wurtzite and monoclinic structures. A metal-semiconductor–metal ultraviolet (UV) photodetector (PD) was also fabricated for the GZO nanosheets. Results revealed that the photoresponses of the GZO UV PD were flat at short wavelengths. Meanwhile, a sharp cutoff was observed at 340 nm. The UV-to-visible rejection ratio of the fabricated PD was \(\sim 89\) at 1 V bias voltage.

In this study, amorphous indium gallium oxide thin-film transistors (IGO TFTs) were fabricated by co-sputtering. Three samples with different deposition powers of the In2O3 target, namely, sample A with 50 W deposition power, sample B with 60 W deposition power, and sample C with 70 W deposition power, were investigated. The device performance revealed that oxygen vacancies are strongly dependent on indium content. However, when the deposition power of the In2O3 target increased, the number of oxygen vacancies, which act as charge carriers to improve the device performance, increased. The best performance was recorded at a threshold voltage of 1.1 V, on-off current ratio of 4.5 &times, 106, and subthreshold swing of 3.82 V/dec in sample B. Meanwhile, the optical properties of sample B included a responsivity of 0.16 A/W and excellent ultraviolet-to-visible rejection ratio of 8 &times, 104. IGO TFTs may act as photodetectors according to the results obtained for optical properties.

This study investigated latent coherence and discrepancy between listening and reading comprehensions. A total of 460 Taiwanese children in the first or second grade participated in this study. Each child was assessed by test materials that contained both spoken and written Chinese tests. Specifically, multiple categorical latent variables (MCLV) models were proposed to assess latent coherence and discrepancy between Mandarin listening and Chinese reading comprehensions. Although notable coherent relations between the two abilities were found, results of this study also indicated that the discrepancy between them should not be ignored. It was concluded that coherence and discrepancy between Mandarin listening skills and Chinese reading performance were quantitatively assessable by the proposed methods. In addition, the discrepancy between the two abilities could be used to assess reading disabilities. Empirical demonstration showed the assessment of Chinese reading disabilities was practically fe...

The bipolar resistive switching characteristics of the Pt/ZnO/Pt resistive random access memory (RRAM) had been investigated. This work introduced UV-Ozone treatment to improve the interface quality between ZnO thin film and Pt electrode. We found that UV-Oznoe can help to clean the surface of Pt electrode and provide superior surface morphology for the subsequent sputtering ZnO thin film deposition. According the experiment result, the Pt/ZnO/Pt RRAM demonstrated better on-off current ratio and the excellent retention time after UV-Ozone treatment.

In this paper, we investigated the effects of dopants on the electrical and optical characteristics of dichromatic and white organic light-emitting devices (OLEDs) with a double emitting layer (DEML). Such a DEML consisted of two host materials with bipolar transport characteristics doped with two distinct types of phosphorescent emitters. The host for EML1 (adjacent to the anode side) was N,N-dicarbazolyl-3,5-benzene (mCP), with a hole mobility higher than the electron mobility, whereas the host for EML2 (adjacent to the cathode side) was 2,2′-bis[5-phenyl-2-(1,3,4)oxadazolyl]biphenyl (OXD), with a higher electron mobility than the hole mobility. Phosphorescent blue emitters, 9% iridium(III)bis[4,6-di-fluorophenyl-pyridinato-N,C2]picolinate (FIrpic), and phosphorescent green emitters, 9% fac-tris(phenylpyridine) iridium [Ir(ppy)3], were doped into EML1 and EML2, respectively for dichromatic emission. In the dichromatic blue/green OLEDs, both the blue and green dopants helped to reduce the driving voltage. The dopants essentially played the role of carrier traps and recombination centers, from which the current density–voltage characteristics and electroluminescence (EL) spectra were derived. In this structure, EML1 and EML2 exhibited hole- and electron-rich bipolar transporting characteristics, respectively. Hence, the recombination was extended to the two EMLs, which reduced the efficiency roll-off and resulted in high efficiency levels even at high luminance levels. Through further incorporation of 0.5% of tris(2-phenylquinoline)iridium(III) [Ir(2-phq)3] into EML1, a white OLED with maximum current efficiency of 35.8 cd/A and quantum efficiency of 10.73% at 0.643 mA/cm2 was obtained. In this white OLED, the current efficiency decreased slightly by 2.51% from 35.8 cd/A at 230 cd/m2 to 34.9 cd/A at 1000 cd/m2. Carrier confinement was achieved at the D-EML interface, which not only contributed to the high current efficiency, but also resulted in stable color coordinates that varied a mere (−0.014, 0.004) from 100 to 10,000 cd/m2, without additional blocking layers between the two EMLs.

We retrospectively reviewed the effectiveness of peripheral sympathectomy for severe Raynaud's phenomenon. In this study, a total of 14 digits from six patients with chronic digital ischemic change were included. All patients had pain, ulcer, or gangrenous change in the affected digits and were unresponsive to pharmacologic or other nonsurgical therapies. In all cases, angiography showed multifocal arterial lesions, so microvascular reconstruction was unfeasible. Peripheral sympathectomy was performed as a salvage procedure to prevent digit amputation. The results were analyzed according to reduction of pain, healing of ulcers, and prevention of amputation. In 12 of the 14 digits, the ulcers healed and amputation was avoided. In the other two digits, the ulcers improved and progressive gangrene was limited. As a salvage procedure for Raynaud's phenomenon recalcitrant to conservative treatment, peripheral sympathectomy improves perfusion to ischemic digits and enables amputation to be avoided.

GaN-based LEDs grown on Si-implanted GaN templates form air gaps beneath the active layer to enhance light-extraction efficiency. GaN-based epitaxial layers grown on selective Si-implanted regions had lower growth rates compared with those grown on implantation-free regions, resulting in selective growth and the subsequent over the Si-implanted regions. Accordingly, air gaps were formed over the Si-implanted regions after the meeting of laterally growing GaN facet fronts. The experimental results indicate that the light-output power of the LEDs grown on the Si-implanted GaN templates was enhanced by 36% compared with conventional LEDs. This enhancement in output power was attributed mainly to the air gaps, which led to a higher escape probability for the photons.

The effect of growth pressure of underlying undoped GaN(u-GaN) layer on the electrical properties of GaN-based light-emitting diodes (LEDs) grown on patterned sapphire substrates (PSS) is evaluated. The electrostatic discharge (ESD) endurance voltages could increase from 4000 to 7000 V when the growth pressure of u-GaN layers is increased from 100 to 500 torr, while the forward voltages and light output powers remain almost the same. Poor ESD endurance ability could be attributed to the underlying GaN layer grown under relative low pressure, which leads to significant surface pits. This could be further attributed to the imperfect coalescence of crystal planes above the convex sapphire patterns. The pits are associated with TDs behaving as a leakage path to degrade electrical performance.

The InGaN/sapphire-based photovoltaic (PV) cells with Al0.14Ga0.86N/In0.21Ga0.79N superlattice structures that serve as absorption layers were grown on patterned sapphire substrates (PSSs). Under global air-mass 1.5 conditions, the short-circuit current density, the open-circuit voltage, and the fill factor obtained from the PV cells were 1.21 mA/cm2, 2.18 V, and 0.65, respectively, corresponding to a conversion efficiency of 1.71%. Compared with PV devices grown on flat sapphire substrates, the photocurrent of PSS-grown PV devices was enhanced by 26%. The improved PV performance was attributable to the positive effects of the PSS on the material quality.

The aim of this study is to provide latent variable models (LVM) to evaluate interaction effects between functional brain cortical regions. Rapidly developed imaging techniques and methods, for instance, ERP and fMRI, can serve as feasible accessories on mapping brain functions by monitoring activities among different cortical regions. Without capable statistical models, for example, the proposed latent variable models, analyzing these complex brain images can be troublesome. The advanced LVM proposed in this study can provide appropriate evaluations on interaction/connectivity among cortical regions that have drawn many attentions in recent cognitive neuroscience literature. We further demonstrate the feasibility of LVM by showing satisfying LVM accuracy rates under various simulated sample sizes and magnitudes of effects in evaluating cortical interactions. Practical suggestions and interpretations of this study are established to serve guidelines for medical and substantive researchers.

The planar flow casting (PFC) process for rapid solidification of metallic materials has been in commercial use to produce thin strips of glassy or microcrystalline materials. The conditions of melt puddle between nozzle and rotating wheel affect significantly the quality and dimensional uniformity of the downstream ribbon. The objective of this research is to develop mathematical model to analyze the combined heat and momentum transfer phenomena during the formation of puddle. The model is based on a computational fluid dynamics technique, called the SOLA-VOF scheme, which possesses the capability of treating transient fluid flow problems with evolution of free boundaries. Furthermore, the principle of enthalpy conservation has also been adapted in the technique to analyze the variation of melt temperature and the corresponding cooling rate of the melt. The simulated results reveal how the melt puddle is formed between the nozzle and the rotating substrate and how changes in process conditions can effect the puddle formation and its corresponding fluid and heat transfer behavior.

Modern Web-server systems use multiple servers to handle an increased user demand. Such systems need effective methods to spread the load among web servers evenly in order to keep web server utilization high while providing sufficient quality of service for end users. In conventional DNS-based load balancing architecture, a Doman Name Server (DNS) dispatches requests to web servers based on their load status. Because web servers need to inform the DNS server about their load status from time to time, a so-called load buffer range is often employed to reduce the update frequency. Without care, however, using a load buffer range may result in load oscillation among web servers. To address this problem, we propose a Random Early Detection (RED) method with the intuition that the probability for a web server to become overloaded in near future is directly proportional to its current load. Simulation confirms that our method helps reducing the oscillation of the web server load significantly.

To cope with rapidly increasing Internet usage nowadays, providing Internet services using multiple servers has become a necessity. To ensure sufficient service quality and server utilization at the same time, effective methods are needed to spread load among servers properly. Existing load balancing methods often assume servers are homogeneous and consider only one type of resource, such as CPU. Such methods suffer from the fact that different requests often demand multiple types of resources with different requirements; trying to balance the usage of only one resource type may induce an inadvertent performance bottleneck, leading to low resource utilization and service quality. To address this problem, we propose a load balancing method based on the concept of distributed market mechanism, where requests are priced with respect to the load of multiple resources on each server. By migrating jobs among servers to balance inter-server load and minimize intra-server job cost at the same time, our method shows significant improvement in terms of load imbalance degrees, server utilization, and response time when compared to other published methods, especially when server heterogeneity increases.

In this article, we have demonstrated the hybrid polymer light-emitting diodes (PLEDs) with a sol-gel derived or rf-sputtered ZnO electron transport layer (ETL). For the ZnO films prepared under different conditions, low annealing temperature (300 °C) leads to the film amorphous while the polycrystalline films is readily achieved by sputtering. Though the surface roughness can be improved by thermal annealing at 400 °C for sputtered films, the release of compressive stress after treatment has shrunk the optical band gap from 3.282 to 3.268 eV. As the ETL in PLEDs, the reduced band gap could increase potential barrier for electron injection and decrease the hole blocking capability. In our cases, luminance larger than 7000 cd/m2 can be obtained in device with pristine sputtered ZnO ETL. It is concluded that crystalline structure of ZnO films is important to facilitate the balance of carrier mobility to obtain high luminance and high efficiency devices.

In this paper, we demonstrate a phosphorescent organic light-emitting device (OLED) with enhanced current efficiency (in terms of cd/A) based on an oxadiazole (OXD) derivative as the electron-transporting host of the emitting layer (EML) doped with a phosphorescent dopant, iridium(III)bis[4,6-(di-fluorophenyl)-pyridinato-N, C2′] picolinate (FIrpic). The maximum current efficiency of OXD-based OLEDs was 13.0 cd/A. Compared to the phosphorescent OLED with a conventional hole-transporting host, 1,3-bis(carbazol-9-yl)benzene (mCP) with 11.1 cd/A in maximum current efficiency, 17.2% improvement was achieved. However, in terms of external quantum efficiency (EQE), the OXD- and mCP-based OLEDs were 4.01 and 4.66%, respectively, corresponding to a 13.9% decrease. Such a discrepancy can be understood from the electroluminescence(EL) variation. Contrary to the hole-transporting mCP, OXD exhibited electron transporting characteristics which shifted the recombination zone toward the anode. The optical interference effect result was that the relative intensity at long wavelengths (500–600 nm) was higher in the OXD-based OLED, which was more sensitive to the human eye and increased the current efficiency, even though the EQE was lower. Besides, in OXD-OLED, the recombination zone shifted toward the anode side with a high driving voltage, which was also deduced from the EL spectral variations. Under a high driving voltage, we observed the relative intensity of FIrpic emission ata longer wavelength increased which resulted from the optical interference effect, and emission from the hole-transporting layer increased. By using hole-transporting mCP and electron-transporting OXD as the hosts of double EML (DEML), the maximum current-efficiency and EQE of the optimized DEML-OLED further increases to 17.6 cd/A and 7.06%, which corresponds to improvements of 58.6% and 51.5%, compared to the single mCP-OLED, and by 35.4% and 76.1%, compared to the single OXD-OLED, respectively. This was a result of the better charge balance in DEML, and less quenching effects from transporting materials.

In this paper, we demonstrated a blue phosphorescent organic light-emitting device (OLED) with a higher current-efficiency and a lower driving-voltage using conventional iridium(III)bis[4,6-(di-fluorophenyl)-pyridinato-N,C2′] picolinate (FIrpic) doped in the double emitting layer (DEML), which consists of a hole- and an electron-transporting material, N,N′-dicarbazolyl-3,5-benzene (mCP) and 2,2′-bis[5-phenyl-2-(1,3,4)oxadazolyl]biphenyl (OXD), respectively. Compared to OLEDs with only single mCP- and OXD-EML, current-efficiency of the optimized DEML-OLED increases by 30.82% and 141.37%, combining with a voltage reduction of 0.34 and 0.59 V at 50 mA/cm2, which comes from the better charge balance in DEML.

In this latter, the authors demonstrated a phosphorescent organic light-emitting device (OLED) with a lower driving voltage and a longer operation lifetime based on 2,2′-bis[5-phenyl-2-(1,3,4)oxadazolyl]biphenyl, an oxadiazole (OXD) derivative, as the host of the emitting layer doped with a common green-emitting phosphorescent dopant, fac-tris(2-phenylpyridine) iridium [Ir(ppy)3]. Rather than an electron transporting materials, the OXD exhibits an ambipolar transport characteristic with suitable Ir(ppy)3 concentrations due to its low highest occupied molecular orbital value (5.9eV) and the hole-transporting characteristics of Ir(ppy)3. It results in a 2.4V voltage reduction and a 2.6 times lifetime elongation of the OXD-based device, as compared to the conventional phosphorescent OLED.

We compared the optical properties and material nanostructures between several InGaN∕GaN multiple quantum-well (QW) samples of different interfacial layers. In some of the samples, InN interfacial layers were inserted between the wells and barriers to improve the QW quality and hence the light-emission efficiency. Compared with a widely used barrier-doped QW structure, the insertions of the InN interfacial layers (silicon doped or undoped) do enhance the photon emission efficiencies. Of the two samples with InN interfacial layers, the one with intrinsic InN interfacial layers had the higher photoluminescence (PL) and electroluminescence (EL) efficiencies. Cluster structures are clearly observed in this sample, resulting in strong carrier localization. In this sample, we also observed a temperature-dependent S-shape variation in the PL spectral peak, a strong photoluminescence excitation (PLE) intensity, and a steep PL decay time variation beyond its peak as a function of temperature. On the other hand, bo...