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1.
ACS Appl Mater Interfaces ; 11(43): 40196-40203, 2019 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-31573173

RESUMO

In this study, the impact of moisture on the electrical characteristics of an amorphous In-Ga-Zn-O thin-film transistor (a-IGZO TFT) was investigated. In commercial applications of such TFTs, high stability and quality performance in humid environments are essential. During TFT operation under ambient moisture, the electrolysis of water molecules occurs via the tip electric field effect. Hydrogen diffuses from the etch-stop layer or back-channel into the main channel under a negative electric field. The hydrogen atoms act as shallow donors (which causes the carrier concentration in the channel to rise), causing the threshold voltage (VTH) to shift in the negative direction. Hydrogen diffusion from the overlap of the source/drain and gate electrodes to the channel center caused by the tip electric field induces a significant barrier lowering and VTH shifts in a short-channel device. However, under negative bias stress (NBS) in ambient moisture, the negative VTH shift is more obvious in short- than in long-channel devices, indicating suppressed hydrogen diffusion in long-channel devices. This is attributed to the electrolysis of water by the tip electric field at the source, drain, and gate electrodes, which causes hydrogen to diffuse to the center of the channel. Here, a novel physical model of the capacitance-voltage (C-V) electrical property changes under ambient moisture is proposed, based on the early appearance of abnormalities in the C-V measurements. The electrolysis of water caused by the tip electric field and electrical abnormalities caused by hydrogen diffusion into the a-IGZO active layer are explained by this model. A secondary-ion mass spectrometry analysis shows that hydrogen content in the channel generally increases under NBS in ambient moisture. The degradation behavior due to moisture in a-IGZO is clarified. Thus, inhibiting the tip electric field may benefit future flexible-display and gas-sensing applications.

2.
ACS Nano ; 12(8): 8748-8757, 2018 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-30071167

RESUMO

Current-injected elliptical nanorod light-emitting diodes (LEDs) are demonstrated to emit polarized light with a bottom-emitting configuration. The polarization ratio of the electroluminescence reaches 3.17 when the length of the minor axis for the elliptical nanorods is as small as 150 nm. Electromagnetic simulation confirms the occurrence of the polarization selectivity especially when the length of the minor axis is down to 150 nm. Light with different polarization travels at different speeds in these asymmetric elliptical nanorods. Only one polarization experiences destructive interference between the light directly from the source and the reflected light by the top metal interface. A thin light-blocking layer is incorporated to increase the polarization selectivity. It is also not recommended to infill the gap with SiO2 since the polarization selectivity will be reduced. The proposed nanorod LEDs are fabricated using top-down nanofabrication approaches by combining nanospherical-lens lithography and two-step etch processes, which are both fully compatible with current semiconductor manufacturing processes. Results in this study will help to develop a chip-level polarization-selecting LED, which will be very useful for applications that require polarized light. It is especially beneficial for applications that are not suitable for using an external polarizer or require polarized light at the individual chip level.

3.
ACS Appl Mater Interfaces ; 10(31): 25866-25870, 2018 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-29481039

RESUMO

This study introduces a cyclical annealing technique that enhances the reliability of amorphous indium-gallium-zinc-oxide (a-IGZO) via-type structure thin film transistors (TFTs). By utilizing this treatment, negative gate-bias illumination stress (NBIS)-induced instabilities can be effectively alleviated. The cyclical annealing provides several cooling steps, which are exothermic processes that can form stronger ionic bonds. An additional advantage is that the total annealing time is much shorter than when using conventional long-term annealing. With the use of cyclical annealing, the reliability of the a-IGZO can be effectively optimized, and the shorter process time can increase fabrication efficiency.

4.
ACS Appl Mater Interfaces ; 9(48): 41845-41854, 2017 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-29134795

RESUMO

A robust and recyclable monolithic substrate applying all-inorganic metal-oxide selective contact with a nanoporous (np) Au:NiOx counter electrode is successfully demonstrated for efficient perovskite solar cells, of which the perovskite active layer is deposited in the final step for device fabrication. Through annealing of the Ni/Au bilayer, the nanoporous NiO/Au electrode is formed in virtue of interconnected Au network embedded in oxidized Ni. By optimizing the annealing parameters and tuning the mesoscopic layer thickness (mp-TiO2 and mp-Al2O3), a decent power conversion efficiency (PCE) of 10.25% is delivered. With mp-TiO2/mp-Al2O3/np-Au:NiOx as a template, the original perovskite solar cell with 8.52% PCE can be rejuvenated by rinsing off the perovskite material with dimethylformamide and refilling with newly deposited perovskite. A renewed device using the recycled substrate once and twice, respectively, achieved a PCE of 8.17 and 7.72% that are comparable to original performance. This demonstrates that the novel device architecture is possible to recycle the expensive transparent conducting glass substrates together with all the electrode constituents. Deposition of stable multicomponent perovskite materials in the template also achieves an efficiency of 8.54%, which shows its versatility for various perovskite materials. The application of such a novel NiO/Au nanoporous electrode has promising potential for commercializing cost-effective, large scale, and robust perovskite solar cells.

5.
Opt Express ; 25(16): A777-A784, 2017 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-29041045

RESUMO

Monolithic stacked InGaN light-emitting diode (LED) connected by a polarization-enhanced GaN/AlN-based tunnel junction is demonstrated experimentally in this study. The typical stacked LEDs exhibit 80% enhancement in output power compared with conventional single LEDs because of the repeated use of electrons and holes for photon generation. The typical operation voltage of stacked LEDs is higher than twice the operation voltage of single LEDs. This high operation voltage can be attributed to the non-optimal tunneling junction in stacked LEDs. In addition to the analyses of experimental results, theoretical analysis of different schemes of tunnel junctions, including diagrams of energy bands, diagrams of electric fields, and current-voltage relation curves, are investigated using numerical simulation. The results shown in this paper demonstrate the feasibility in developing cost-effective and highly efficient tunnel-junction LEDs.

6.
Adv Mater ; 28(17): 3290-7, 2016 05.
Artigo em Inglês | MEDLINE | ID: mdl-26928274

RESUMO

UNLABELLED: The successful application of a Ni/Au transparent electrode for fabricating efficient perovskite-based solar cells is demonstrated. Through interdiffusion of the Ni/Au bilayer, Au forms an interconnected metallic network structure as the transparent electrode. Ni diffuses to the bilayer surface and oxidizes into NiOx becoming an appropriate electrode interlayer. These ITO- and PEDOT: PSS-free devices have potential applications in the design of future cost-effective, low-weight, and stable solar cells.

7.
Opt Express ; 23(7): A337-45, 2015 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-25968799

RESUMO

We demonstrate indium gallium nitride/gallium nitride/aluminum nitride (AlN/GaN/InGaN) multi-quantum-well (MQW) ultraviolet (UV) light-emitting diodes (LEDs) to improve light output power. Similar to conventional UV LEDs with AlGaN/InGaN MQWs, UV LEDs with AlN/GaN/InGaN MQWs have forward voltages (V(f)'s) ranging from 3.21 V to 3.29 V at 350 mA. Each emission peak wavelength of AlN/GaN/InGaN MQW UV LEDs presents 350 mA output power greater than that of the corresponding emission peak wavelength of AlGaN/InGaN MQW UV LEDs. The light output power at 350mA of AlN/GaN/InGaN MQWs UV LEDs with 375 nm emission wavelength can reach around 26.7% light output power enhancement in magnitude compared to the AlGaN/InGaN MQWs UV LEDs with same emission wavelength. But 350mA light output power of AlN/GaN/InGaN MQWs UV LEDs with emission wavelength of 395nm could only have light output power enhancement of 2.43% in magnitude compared with the same emission wavelength AlGaN/InGaN MQWs UV LEDs. Moreover, AlN/GaN/InGaN MQWs present better InGaN thickness uniformity, well/barrier interface quality and less large size pits than AlGaN/InGaN MQWs, causing AlN/GaN/InGaN MQW UV LEDs to have less reverse leakage currents at -20 V. Furthermore, AlN/GaN/InGaN MQW UV LEDs have the 2-kV human body mode (HBM) electrostatic discharge (ESD) pass yield of 85%, which is 15% more than the 2-kV HBM ESD pass yield of AlGaN/InGaN MQW UV LEDs of 70%.

8.
Opt Express ; 23(7): A401-12, 2015 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-25968805

RESUMO

Non-planar InGaN/GaN multiple quantum well (MQW) structures are grown on a GaN template with truncated hexagonal pyramids (THPs) featuring c-plane and r-plane surfaces. The THP array is formed by the regrowth of the GaN layer on a selective-area Si-implanted GaN template. Transmission electron microscopy shows that the InGaN/GaN epitaxial layers regrown on the THPs exhibit different growth rates and indium compositions of the InGaN layer between the c-plane and r-plane surfaces. Consequently, InGaN/GaN MQW light-emitting diodes grown on the GaN THP array emit multiple wavelengths approaching near white light.

9.
BMC Pulm Med ; 14: 115, 2014 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-25022445

RESUMO

BACKGROUND: Glutamine (GLN) has been reported to improve clinical and experimental sepsis outcomes. However, the mechanisms underlying the actions of GLN remain unclear, and may depend upon the route of GLN administration and the model of acute lung injury (ALI) used. The aim of this study was to investigate whether short-term GLN supplementation had an ameliorative effect on the inflammation induced by direct acid and lipopolysaccharide (LPS) challenge in mice. METHODS: Female BALB/c mice were divided into two groups, a control group and a GLN group (4.17% GLN supplementation). After a 10-day feeding period, ALI was induced by intratracheal administration of hydrochloric acid (pH 1.0; 2 mL/kg of body weight [BW]) and LPS (5 mg/kg BW). Mice were sacrificed 3 h after ALI challenge. In this early phase of ALI, serum, lungs, and bronchoalveolar lavage fluid (BALF) from the mice were collected for further analysis. RESULTS: The results of this study showed that ALI-challenged mice had a significant increase in myeloperoxidase activity and expression of interleukin (IL)-1ß, IL-6, and tumor necrosis factor-α in the lung compared with unchallenged mice. Compared with the control group, GLN pretreatment in ALI-challenged mice reduced the levels of receptor for advanced glycation end-products (RAGE) and IL-1ß production in BALF, with a corresponding decrease in their mRNA expression. The GLN group also had markedly lower in mRNA expression of cyclooxygenase-2 and NADPH oxidase-1. CONCLUSIONS: These results suggest that the benefit of dietary GLN may be partly contributed to an inhibitory effect on RAGE expression and pro-inflammatory cytokines production at an early stage in direct acid and LPS-induced ALI in mice.


Assuntos
Lesão Pulmonar Aguda/tratamento farmacológico , Lesão Pulmonar Aguda/metabolismo , Glutamina/administração & dosagem , Pneumonia/tratamento farmacológico , Pneumonia/metabolismo , RNA Mensageiro/metabolismo , Receptores Imunológicos/metabolismo , Lesão Pulmonar Aguda/induzido quimicamente , Animais , Líquido da Lavagem Broncoalveolar , Ciclo-Oxigenase 2/genética , Suplementos Nutricionais , Ativação Enzimática/efeitos dos fármacos , Feminino , Ácido Clorídrico , Interleucina-1beta/genética , Interleucina-1beta/metabolismo , Interleucina-6/metabolismo , Lipopolissacarídeos , Camundongos , Camundongos Endogâmicos BALB C , NADH NADPH Oxirredutases/genética , NADPH Oxidase 1 , Peroxidase/metabolismo , Pneumonia/induzido quimicamente , Receptor para Produtos Finais de Glicação Avançada , Receptores Imunológicos/genética , Fator de Necrose Tumoral alfa/metabolismo
10.
Opt Express ; 22(9): 11340-50, 2014 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-24921831

RESUMO

A high-aspect-ratio metallic rod array is demonstrated to generate and propagate highly confined terahertz (THz) surface plasmonic waves under end-fire excitation. The transverse modal power distribution and spectral properties of the bound THz plasmonic wave are characterized in two metallic rod arrays with different periods and in two configurations with and without attaching a subwavelength superstrate. The integrated metallic rod array-based waveguide can be used to sense the various thin films deposited on the polypropylene superstrate based on the phase-sensitive mechanism. The sensor exhibits different phase detection sensitivities depending on the modal power immersed in the air gaps between the metallic rods. Deep-subwavelength SiO(2) and ZnO nanofilms with an optical path difference of 252 nm, which is equivalent to λ/3968 at 0.300 THz, are used as analytes to test the integrated plasmonic waveguide. Analysis of the refractive index and thickness of molecular membranes indicates that the metallic rod array-based THz waveguide can integrate various biochip platforms for minute molecular detection, which is extremely less than the coherent length of THz waves.

11.
Opt Express ; 22 Suppl 2: A396-401, 2014 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-24922249

RESUMO

We have demonstrated a gallium nitride (GaN)-based green light-emitting diode (LED) with graphene/indium tin oxide (ITO) transparent contact. The ohmic characteristic of the p-GaN and graphene/ITO contact could be preformed by annealing at 500 °C for 5 min. The specific contact resistance of p-GaN/graphene/ITO (3.72E-3 Ω·cm²) is one order less than that of p-GaN/ITO. In addition, the 20-mA forward voltage of LEDs with graphene/ITO transparent (3.05 V) is 0.09 V lower than that of ITO LEDs (3.14 V). Besides, We have got an output power enhancement of 11% on LEDs with graphene/ITO transparent contact.

12.
Opt Express ; 22 Suppl 3: A633-41, 2014 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-24922371

RESUMO

Compared with conventionally grown thin InGaN wells, thick InGaN wells with digitally grown InN/GaN exhibit superior optical properties. The activation energy (48 meV) of thick InGaN wells (generated by digital InN/GaN growth from temperature-dependent integrated photoluminescence intensity) is larger than the activation energy (25 meV) of conventionally grown thin InGaN wells. Moreover, thick InGaN wells with digitally grown InN/GaN exhibit a smaller σ value (the degree of localization effects) of 19 meV than that of conventionally grown thin InGaN wells (23 meV). Compared with green light-emitting diodes (LEDs) with conventional thin InGaN wells, the improvement in 20-A/cm² output power for LEDs containing thick InGaN wells with digitally grown InN/GaN is approximately 23%.

13.
Opt Express ; 22 Suppl 3: A663-70, 2014 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-24922374

RESUMO

The operating voltage, light output power, and efficiency droops of GaN-based light emitting diodes (LEDs) were improved by introducing Mg-doped AlGaN/InGaN superlattice (SL) electron blocking layer (EBL). The thicker InGaN layers of AlGaN/InGaN SL EBL could have a larger effective electron potential height and lower effective hole potential height than that of AlGaN EBL. This thicker InGaN layer could prevent electron leakage into the p-region of LEDs and improve hole injection efficiency to achieve a higher light output power and less efficiency droops with the injection current. The low lateral resistivity of Mg-doped AlGaN/InGaN SL would have superior current spreading at high current injection.

14.
Opt Express ; 21 Suppl 5: A864-71, 2013 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-24104581

RESUMO

GaN-based blue light-emitting diodes (LEDs) with micro truncated hexagonal pyramid (THP) array were grown on selective-area Si-implanted GaN (SIG) templates. The GaN epitaxial layer regrown on the SIG templates exhibited selective growth and subsequent lateral growth to form the THP array. The observed selective-area growth was attributed to the different crystal structures between the Si-implanted and implantation-free regions. Consequently, LEDs grown on the GaN THP array emitted broad electroluminescence spectra with multiple peaks. Spatially resolved cathodoluminescence revealed that the broad spectra originated from different areas within each THP. Transmission electron microscopy showed the GaN-based epitaxial layers, including InGaN/GaN multi-quantum wells regrown at different growth rates (or with different In content in the InGaN wells) between the semi-polar and c-face planes of each THP.

15.
Opt Lett ; 38(16): 3158-61, 2013 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-24104675

RESUMO

In blue InGaN light-emitting diodes (LEDs), the intuitive approaches to suppress Auger recombination by reducing carrier density, e.g., increasing the number of quantum wells (QWs) and thickening the width of wells, suffer from nonuniform carrier distribution and more severe spatial separation of electron and hole wave functions. To resolve this issue, LED structures with thick InGaN wells and polarization-matched AlGaInN barriers are proposed theoretically. Furthermore, the number of QWs is reduced for the purpose of mitigating the additional compressive strain in AlGaInN barriers. Simulation results reveal that, in the proposed structures, the quantum-confined Stark effect in strained wells is nearly eliminated through the utilization of polarization-matched barriers, which efficiently promotes internal quantum efficiency. Furthermore, the phenomenon of efficiency droop is also markedly improved because of the uniformly distributed or dispersed carriers, and accordingly the suppressed Auger recombination.

16.
Conf Proc IEEE Eng Med Biol Soc ; 2013: 5489-92, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24110979

RESUMO

This paper presents a low-power wireless ECG acquisition system-on-chip (SoC), including an RF front-end circuit, a power unit, an analog front-end circuit, and a digital circuitry. The proposed RF front-end circuit can provide the amplitude shift keying demodulation and distance to digital conversion to accurately receive the data from the reader. The received data will wake up the power unit to provide the required supply voltages of analog front-end (AFE) and digital circuitry. The AFE, including a pre-amplifier, an analog filter, a post-amplifier, and an analog-to-digital converter, is used for the ECG acquisition. Moreover, the EPC Class I Gen 2 UHF standard is employed in the digital circuitry for the handshaking of communication and the control of the system. The proposed SoC has been implemented in 0.18-µm standard CMOS process and the measured results reveal the communication is compatible to the RFID protocol. The average power consumption for the operating chip is 12 µW. Using a Sony PR44 battery to the supply power (605mAh@1.4V), the RFID tag SoC operates continuously for about 50,000 hours (>5 years), which is appropriate for wireless wearable ECG monitoring systems.


Assuntos
Eletrocardiografia/instrumentação , Monitorização Fisiológica/instrumentação , Dispositivo de Identificação por Radiofrequência , Processamento de Sinais Assistido por Computador/instrumentação , Tecnologia sem Fio/instrumentação , Desenho de Equipamento
17.
Dalton Trans ; 42(36): 13161-71, 2013 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-23880878

RESUMO

A new series of ruthenium(II) carbonyl complexes with benzene-based CCC-pincer bis-(carbene) ligands, [((R)CCC(R))Ru(CO)2(X)](0/+) and [((R)CCC(R))Ru(CO)(NN)](+) ((R)CCC(R) = 2,6-bis-(1-alkylimidazolylidene)benzene, R = Me or (n)Bu; X = I, Br, CH3CN, or 6-(aminomethyl)pyridine (ampy); NN = 2·CH3CN, or chelating ampy or bipyridine), was synthesized and fully characterized. X-Ray structure determinations revealed that these eight complexes have pseudo-octahedral configurations around the ruthenium center with the pincer ligand occupying three meridional sites. These complexes prove to be efficient precatalysts demonstrating very good activity and reusability for the transfer hydrogenation of ketones.

18.
Opt Express ; 21(8): 9643-51, 2013 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-23609674

RESUMO

The present study demonstrates the optoelectrical and low-frequency noise characteristics of ZnO-SiO(2) nanocomposite solar-blind metal-semiconductor-metal photodetectors (MSM PDs) on flexible polyethersulfone (PES) substrate with and without an organosilicon [SiO(x)(CH(3))] buffer layer. For a given bandwidth of 100 Hz and a -5 V applied bias, the noise equivalent powers of the ZnO-SiO(2) nanocomposite MSM PD on PES with and without the SiO(x)(CH(3)) buffer layer were 1.39 × 10(-14) and 5.72 × 10(-14) W at 240nm, respectively, corresponding to the normalized detectivities of 5.04 × 10(14) and 1.22 × 10(14) Hz(0.5) W(-1), respectively. These findings indicate that a lower noise level and a higher detectivity can be achieved for ZnO-SiO(2) nanocomposite MSM PDs on PES by introducing a SiO(x)(CH(3)) buffer layer.


Assuntos
Compostos Orgânicos/química , Fotometria/instrumentação , Semicondutores , Dióxido de Silício/química , Óxido de Zinco/química , Condutividade Elétrica , Desenho de Equipamento , Análise de Falha de Equipamento , Luz , Compostos Orgânicos/efeitos da radiação , Razão Sinal-Ruído , Dióxido de Silício/efeitos da radiação , Óxido de Zinco/efeitos da radiação
19.
Opt Express ; 20 Suppl 6: A1019-25, 2012 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-23187653

RESUMO

We present an efficient vertical InGaN light-emitting diode (LED) in which the proposed vertical LEDs were fabricated with patterned sapphire substrates (PSS) using thinning techniques. After the thinning of sapphire substrate, selective dry etching process was performed on the remainder sapphire layer to expose the n-GaN contact layer instead of removing the sapphire substrate using the laser lift-off technique. These processes feature the LEDs with a sapphire-face-up structure and vertical conduction property. The PSS was adopted as a growth substrate to mitigate the light-guided effect, and thereby increase the light-extraction efficiency. Compared with conventional lateral GaN LEDs grown on PSS, the proposed vertical LEDs exhibit a higher light output power and less power degradation at a high driving current. This could be attributed to the fact that the vertical LEDs behave in a manner similar to flip-chip GaN/sapphire LEDs with excellent heat conduction.

20.
Opt Express ; 20(18): 19635-42, 2012 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-23037016

RESUMO

Sputtered ZnO-SiO2 nanocomposite light-emitting diodes (LEDs) were treated using a flat-top nanosecond laser (FTNL) under room temperature. The intensity of the 376 nm electroluminescence (EL) emission of ZnO-SiO2 nanocomposite LEDs at a current of 9 mA with FTNL treatment was approximately 1.4 times greater than LEDs without FTNL treatment. Furthermore, the FTNL-treated LEDs indicated a narrower full width at half maximum of the 376 nm EL emission than those of LEDs without FTNL treatment. Thus, FTNL treatment of ZnO-SiO2 nanocomposite LEDs could induce the recrystallization of distributed ZnO nanoclusters and reduce the defects in ZnO-SiO2 nanocomposite layers.


Assuntos
Iluminação/instrumentação , Nanoestruturas/química , Nanotecnologia/instrumentação , Semicondutores , Desenho de Equipamento , Análise de Falha de Equipamento , Temperatura Alta , Lasers , Nanoestruturas/efeitos da radiação
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