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1.
Nanotechnology ; 31(36): 365702, 2020 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-32442986

RESUMO

With additional precursor soaking, a thin Al2O3 dielectric layer can be grown on mono-layer MoS2 by using atomic layer deposition (ALD). Similar optical characteristics are observed before and after ALD growth for the mono-layer MoS2, which indicates that minor damage to the thin 2D material film is introduced during the growth procedure. With the thin separation layer, luminescence enhancement and dual-color emission are observed by transferring MoS2 and WS2 mono-layer 2D materials to 5 nm Al2O3/mono-layer MoS2 samples, respectively. The results demonstrate that with careful treatment of the interfaces of 2D crystals with other materials, different stacked structures can be established.

2.
J Nanosci Nanotechnol ; 20(3): 1704-1708, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31492333

RESUMO

In this study, the optical and electrical properties of a zinc tin oxide (ZTO) thin-film transistor (TFT) were investigated. The TFT was fabricated using ZTO as the active layer, which was deposited by a radio frequency magnetron sputtering system, to form an ultraviolet (UV) photodetector. The device has a threshold voltage of 0.48 V, field-effect mobility of 1.47 cm²/Vs in the saturation region, on/off drain current ratio of 2×106, and subthreshold swing of 0.45 V/decade in a dark environment. Moreover, as a UV photodetector, the device has a long photoresponse time, responsivity of 0.329 A/W, and rejection ratio of 3.19×104 at a gate voltage of -15 V under illumination of wavelength 300 nm.

3.
ACS Omega ; 4(22): 19847-19855, 2019 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-31788617

RESUMO

In this study, a flexible and stable pH sensor based on aluminum-doped zinc oxide nanosheets (Al-doped ZnO NSs) was developed by a low-cost hydrothermal method. The results obtained from this study indicated that Al ions could be doped successfully into the ZnO nanostructure, which could change the morphology and improve the pH-sensing properties. The pH sensitivity of Al-doped ZnO nanosheets reached 50.2 mV/pH with a correlation coefficient of around 0.99468 when compared with that of ZnO film (34.13 mV/pH) and pure ZnO nanowires (45.89 mV/pH). The test range of pH values was widened by Al-doping, and the Al-doped ZnO NS sensor could detect the pH value ranging from 2 to 12. It was observed that in a more acidic environment, especially at pH 2, the sensor, Al-doped ZnO nanosheet, was strongly stable over 12 weeks of testing. It was noted that the response time was utterly fast and the response time of the sensors for each pH standard buffer solutions was around 0.3 s. Thus, the response time and performance were quite stable. The microchannel provided a novel testing method for the pH sensor, where the liquid to be tested was just 5 mL. Hence, it was suggested to be useful for many medical diagnoses and treatments. The benefits of Al-doped ZnO nanosheet pH sensor were high sensitivity, good long-term usage, good flexible property, and requirement of a small amount of test liquid, which could make the sensors viable candidates for practical applications.

4.
IEEE Trans Biomed Eng ; 65(9): 2052-2057, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29989940

RESUMO

A nonenzymatic glucose photobiosensor was developed based on Au-nanoparticle-decorated TiO2 nanorods (NRs) under visible illumination. Au nanoparticles (NPs) absorbed the visible illumination, resulting in surface plasmon resonance (SPR). The SPR of the Au NPs indicated that there was a strong electric field around them, which promoted the transport of more electrons to the TiO2 NRs and enhanced the glucose sensing properties. The sensing current under visible illumination was five times higher than in the dark when in 0.1 M NaOH solution at a potential of 0.17 V. Moreover, the Michaelis-Menten constant (Km) of the Au NPs/TiO2 NRs/FTO under visible illumination was 0.52 mM, which is much smaller than that reported previously. Moreover, these results indicate that the Au NPs/TiO2 NRs/FTO under visible illumination feature outstanding properties as a nonenzymatic glucose photobiosensor.


Assuntos
Glucose/análise , Ouro/química , Nanopartículas Metálicas/química , Ressonância de Plasmônio de Superfície/instrumentação , Ressonância de Plasmônio de Superfície/métodos , Titânio/química , Luz , Nanotubos/química
5.
J Nanosci Nanotechnol ; 18(2): 1202-1206, 2018 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-29448558

RESUMO

The ZnO nanostructure environmental sensors were prepared via the three-dimensional through silicon via (3D-TSV) technique. For 3D-TSV, the diameter and length of the Si via were about 200 and 400 µm, respectively. For nitrogen oxide (NO), the measured responses were around ~12, ~16, and ~20% when the concentrations of the injected NO gas were 20, 40 and 60 ppm, respectively. For humidity and temperature sensing, the measured nanowire current increased logarithmically with increasing chamber temperature. The response to relative humidity increased with increasing temperature.

6.
J Nanosci Nanotechnol ; 18(7): 4930-4934, 2018 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-29442676

RESUMO

Zinc-tin-oxide thin-film transistors were prepared by radio frequency magnetron co-sputtering, while an identical zinc-tin-oxide thin film was deposited simultaneously on a clear glass substrate to facilitate measurements of the optical properties. When we adjusted the deposition power of ZnO and SnO2, the bandgap of the amorphous thin film was dominated by the deposition power of SnO2. Since the thin-film transistor has obvious absorption in the ultraviolet region owing to the wide bandgap, the drain current increases with the generation of electron-hole pairs. As part of these investigations, a zinc-tin-oxide thin-film transistor has been fabricated that appears to be very promising for ultraviolet applications.

7.
J Nanosci Nanotechnol ; 18(5): 3518-3522, 2018 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-29442860

RESUMO

In this study, zinc indium tin oxide thin-film transistors (ZITO TFTs) were fabricated by the radio frequency (RF) sputtering deposition method. Adding indium cations to ZnO by co-sputtering allows the development of ZITO TFTs with improved performance. Material characterization revealed that ZITO TFTs have a threshold voltage of 0.9 V, a subthreshold swing of 0.294 V/decade, a field-effect mobility of 5.32 cm2/Vs, and an on-off ratio of 4.7 × 105. Furthermore, an investigation of the photosensitivity of the fabricated devices was conducted by an illumination test. The responsivity of ZITO TFTs was 26 mA/W, with 330-nm illumination and a gate bias of -1 V. The UV-to-visible rejection ratio for ZITO TFTs was 2706. ZITO TFTs were observed to have greater UV light sensitivity than that of ZnO TFTs. We believe that these results suggest a significant step toward achieving high photosensitivity. In addition, the ZITO semiconductor system could be a promising candidate for use in high performance transparent TFTs, as well as further sensing applications.

8.
ACS Omega ; 3(10): 13798-13807, 2018 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-31458079

RESUMO

An ultraviolet-enhanced (UV-enhanced) nitric oxide (NO) sensor based on silver-doped zinc oxide (ZnO) nanoflowers is developed using a low-cost hydrothermal method. The results indicate that silver (Ag) ions were doped into the ZnO nanostructure successfully, thus changing the morphology. In the high-resolution transmission electron microscopy images, we also found that some Ag ions were separated out onto the surface of the ZnO nanoflowers and that the Ag-doped and Ag nanoparticles improved the sensing property. The NO sensing property increased from 73.91 to 89.04% through the use of a UV light-emitting diode (UV-LED). The response time was approximately 120 s without the UV-LED, and the UV-enhanced Ag-doped ZnO nanoflower sensor exhibited a reduced response time (60 s). The best working temperature could be reduced from 200 to 150 °C using UV light illumination, and it was found that the NO response increased by 15.13% at 150 °C. The UV photoresponse of the Ag-doped ZnO nanoflowers and the mechanisms by which the improvement of NO sensing property occurred through the use of UV light illumination are discussed. The property of the gas sensor can be calibrated using a self-photoelectric effect under UV light illumination. These interesting UV-enhanced Ag-doped ZnO nanoflowers are viable candidates for practical applications.

9.
Materials (Basel) ; 10(2)2017 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-28772487

RESUMO

We investigated the electrical and optoelectronic properties of a magnesium zinc oxide thin-film phototransistor. We fabricate an ultraviolet phototransistor by using a wide-bandgap MgZnO thin film as the active layer material of the thin film transistor (TFT). The fabricated device demonstrated a threshold voltage of 3.1 V, on-off current ratio of 105, subthreshold swing of 0.8 V/decade, and mobility of 5 cm²/V·s in a dark environment. As a UV photodetector, the responsivity of the device was 3.12 A/W, and the rejection ratio was 6.55 × 105 at a gate bias of -5 V under 290 nm illumination.

10.
Nanomaterials (Basel) ; 7(7)2017 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-28672868

RESUMO

Indium titanium zinc oxide (InTiZnO) as the channel layer in thin film transistor (TFT) grown by RF sputtering system is proposed in this work. Optical and electrical properties were investigated. By changing the oxygen flow ratio, we can suppress excess and undesirable oxygen-related defects to some extent, making it possible to fabricate the optimized device. XPS patterns for O 1s of InTiZnO thin films indicated that the amount of oxygen vacancy was apparently declined with the increasing oxygen flow ratio. The fabricated TFTs showed a threshold voltage of -0.9 V, mobility of 0.884 cm²/Vs, on-off ratio of 5.5 × 105, and subthreshold swing of 0.41 V/dec.

11.
ACS Appl Mater Interfaces ; 9(17): 14935-14944, 2017 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-28414425

RESUMO

UV- and visible-light photoresponse was achieved via p-type K-doped ZnO nanowires and nanosheets that were hydrothermally synthesized on an n-ZnO/glass substrate and peppered with Au nanoparticles. The K content of the p-ZnO nanostructures was 0.36 atom %. The UV- and visible-light photoresponse of the p-ZnO nanostructures/n-ZnO sample was roughly 2 times higher than that of the ZnO nanowires. The Au nanoparticles of various densities and diameter sizes were deposited on the p-ZnO nanostructures/n-ZnO samples by a simple UV photochemical reaction method yielding a tunable and enhanced UV- and visible-light photoresponse. The maximum UV and visible photoresponse of the Au nanoparticle sample was obtained when the diameter size of the Au nanoparticle was approximately 5-35 nm. On the basis of the localized surface plasmon resonance effect, the UV, blue, and green photocurrent/dark current ratios of Au nanoparticle/p-ZnO nanostructures/n-ZnO are ∼1165, ∼94.6, and ∼9.7, respectively.

12.
J Phys Chem B ; 121(14): 2931-2941, 2017 04 13.
Artigo em Inglês | MEDLINE | ID: mdl-28328226

RESUMO

Au/ZnO core-shell nanostructures decorated with Au nanoparticles were synthesized on an ITO/glass substrate. The investigated sensor contains 2-D, 1-D, and 0-D nanostructures to provide a large surface-area-to-volume ratio and catalytic quantum effect and to avoid the issues inherent in heterojunction interface barriers. The sensitivities of the fabricated glucose sensors in the dark and under blue and green LED illumination were 3371.9, 4410.9, and 4157.8 µA/cm2 mM-1, respectively. The achieved sensitivities are higher than previous reports on Au nanostructure sensors by 2-100 times. Further, the blue and green LED illumination respectively enhanced the sensitivity and CV glucose sensing currents by ∼30.8 and ∼23.3% and ∼27 and ∼35%. The detection limits of the glucose sensor in the dark and under visible illumination were the same at ∼0.5 µM. Moreover, these visible light illumination enhancements are attributed to the localized surface plasmon resonance effect.


Assuntos
Técnicas Eletroquímicas , Glucose/análise , Luz , Medições Luminescentes , Nanoestruturas/química , Ouro/química , Propriedades de Superfície , Óxido de Zinco/química
13.
Materials (Basel) ; 9(5)2016 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-28773483

RESUMO

An investigation of the photoluminescent properties and crystalline morphology of blue emitting LiBa1-xPO4:xTm3+ phosphors with various concentrations (x = 0.005-0.030) of Tm3+ ions were synthesized by microwave sintering. For comparison, the LiBa1-xPO4:xTm3+ powders sintered at the same sintering condition but in a conventional furnace were also investigated. LiBaPO4 without second phase was formed no matter which furnace was used. More uniform grain size distributions are obtained by microwave sintering. When the concentration of Tm3+ ion was x = 0.015, the luminescence intensity reached a maximum value, and then decreased with the increases of the Tm3+ concentration due to concentration quenching effect. The microwave sintering significantly enhanced the emission intensity of LiBa1-xPO4:xTm3+ phosphors. Additionally, the d-d interaction is the key mechanism of concentration quenching for LiBaPO4:Tm3+. The chromaticity (x, y) for all LiBa1-xPO4:xTm3+ phosphors are located at (0.16, 0.05), which will be classified as a blue region.

14.
Materials (Basel) ; 9(7)2016 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-28773678

RESUMO

In this paper, the oil-in-gelatin based tissue-mimicking materials (TMMs) doped with carbon based materials including carbon nanotube, graphene ink or lignin were prepared. The volume percent for gelatin based mixtures and oil based mixtures were both around 50%, and the doping amounts were 2 wt %, 4 wt %, and 6 wt %. The effect of doping material and amount on the microwave dielectric properties including dielectric constant and conductivity were investigated over an ultra-wide frequency range from 2 GHz to 20 GHz. The coaxial open-ended reflection technology was used to evaluate the microwave dielectric properties. Six measured values in different locations of each sample were averaged and the standard deviations of all the measured dielectric properties, including dielectric constant and conductivity, were less than one, indicating a good uniformity of the prepared samples. Without doping, the dielectric constant was equal to 23 ± 2 approximately. Results showed with doping of carbon based materials that the dielectric constant and conductivity both increased about 5% to 20%, and the increment was dependent on the doping amount. By proper selection of doping amount of the carbon based materials, the prepared material could map the required dielectric properties of special tissues. The proposed materials were suitable for the phantom used in the microwave medical imaging system.

15.
Opt Lett ; 40(12): 2878-81, 2015 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-26076285

RESUMO

A ZnO-nanowire photodetector was prepared using three-dimensional through silicon via (TSV) technology. The diameter and depth of the Si via were about 80 µm and 170 µm, respectively. Cu uniformly filled in each TSV, whose average resistance was about 0.9 mΩ. For the three-dimensional ZnO-nanowire photodetector, the photocurrent increased rapidly with a time constant of about 1 s when ultraviolet excitation was applied. The on-off current ratio was about 104.

16.
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%.

17.
Nanoscale Res Lett ; 10: 122, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25852415

RESUMO

This paper presents a facile solvothermal method of synthesizing copper indium sulfide (CuInS2) quantum dots (QDs) via a non-coordinated system using polyetheramine as a solvent. The structural and optical properties of the resulting CuInS2 QDs were investigated using composition analysis, absorption spectroscopy, and emission spectroscopy. We employed molar ratios of I, III, and VI group elements to control the structure of CuInS2 QDs. An excess of group VI elements facilitated precipitation, whereas an excess of group I elements resulted in CuInS2 QDs with high photoluminescence quantum yield. The emission wavelength and photoluminescence quantum yield could also be modulated by controlling the composition ratio of Cu and In in the injection stock solution. An increase in the portion of S shifted the emission wavelength of the QDs to a shorter wavelength and increased the photoluminescence quantum yield. Our results demonstrate that the band gap of the CuInS2 QDs is tunable with size as well as the composition of the reactant. The photoluminescence quantum yield of the CuInS2 QDs ranged between 0.7% and 8.8% at 250°C. We also determined some important physical parameters such as the band gaps and energy levels of this system, which are crucial for the application of CuInS2 nanocrystals.

18.
ACS Appl Mater Interfaces ; 7(12): 6683-9, 2015 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-25769080

RESUMO

In this study, we investigate the effects of fluorinated poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) buffer layer on the performance of polymer photovoltaic cells. We demonstrate for the first time, the deterioration of the device performance can be effectively mended by modifying the interface between the active layer and buffer layer with heptadecafluoro-1,1,2,2-tetra-hydro-decyl trimethoxysilane (PFDS) and perfluorononane. Device performance shows a substantial enhancement of short-circuit current from 7.90 to 9.39 mA/cm(2) and fill factor from 27% to 53%. The overall device efficiency was improved from 0.98% to 3.12% for PFDS modified device. The mechanism of S-shape curing is also discussed. In addition, the stability of modified devices shows significant improvement than those without modification. The efficiency of the modified devices retains about half (1.88%) of its initial efficiency (4.1%) after 30 d compared to the unmodified ones (0.61%), under air atmosphere.

19.
Appl Opt ; 53(31): 7285-9, 2014 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-25402889

RESUMO

In this study, we theoretically investigate the near-infrared (NIR) photonic band structure (PBS) in a one-dimensional semiconductor metamaterial (MM) photonic crystal (PC). The considered PC is (AB)N, where N is the stack number, A is a dielectric, and B is a semiconductor MM composed of Al-doped ZnO and ZnO. It is found that the photonic band gaps (PBGs) can be tunable by the variations in filling factor, and thicknesses of A and B. It is of particular interest to see that the PBG will vanish when the thicknesses of A and B satisfy a certain condition. The results provide fundamental information on a NIR PBS that could be of technical use in photonic applications using such a semiconductor MM. The band gap vanishing makes it possible to design a wider band pass filter at NIR based on the use of such a PC.

20.
Small ; 10(22): 4562-85, 2014 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-25319960

RESUMO

In the past decades, the doping of ZnO one-dimensional nanostructures has attracted a great deal of attention due to the variety of possible morphologies, large surface-to-volume ratios, simple and low cost processing, and excellent physical properties for fabricating high-performance electronic, magnetic, and optoelectronic devices. This article mainly concentrates on recent advances regarding the doping of ZnO one-dimensional nanostructures, including a brief overview of the vapor phase transport method and hydrothermal method, as well as the fabrication process for photodetectors. The dopant elements include B, Al, Ga, In, N, P, As, Sb, Ag, Cu, Ti, Na, K, Li, La, C, F, Cl, H, Mg, Mn, S, and Sn. The various dopants which act as acceptors or donors to realize either p-type or n-type are discussed. Doping to alter optical properties is also considered. Lastly, the perspectives and future research outlook of doped ZnO nanostructures are summarized.


Assuntos
Nanoestruturas , Óxido de Zinco/química , Microscopia Eletrônica de Varredura
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