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21 pages, 5317 KiB

Open AccessArticle

Ga₂O₃(Sn) Oxides for High-Temperature Gas Sensors

by Nataliya Vorobyeva, Marina Rumyantseva, Vadim Platonov, Darya Filatova, Artem Chizhov, Artem Marikutsa, Ivan Bozhev and Alexander Gaskov

Nanomaterials 2021, 11(11), 2938; https://doi.org/10.3390/nano11112938 - 2 Nov 2021

Cited by 21 | Viewed by 3442

Abstract

Gallium(III) oxide is a promising functional wide-gap semiconductor for high temperature gas sensors of the resistive type. Doping of Ga₂O₃ with tin improves material conductivity and leads to the complicated influence on phase content, microstructure, adsorption sites, donor centers and, [...] Read more.

Gallium(III) oxide is a promising functional wide-gap semiconductor for high temperature gas sensors of the resistive type. Doping of Ga₂O₃ with tin improves material conductivity and leads to the complicated influence on phase content, microstructure, adsorption sites, donor centers and, as a result, gas sensor properties. In this work, Ga₂O₃ and Ga₂O₃(Sn) samples with tin content of 0–13 at.% prepared by aqueous co-precipitation method were investigated by X-ray diffraction, nitrogen adsorption isotherms, X-ray photoelectron spectroscopy, infrared spectroscopy and probe molecule techniques. The introduction of tin leads to a decrease in the average crystallite size, increase in the temperature of β-Ga₂O₃ formation. The sensor responses of all Ga₂O₃(Sn) samples to CO and NH₃ have non-monotonous character depending on Sn content due to the following factors: the formation of donor centers and the change of free electron concentration, increase in reactive chemisorbed oxygen ions concentration, formation of metastable Ga₂O₃ phases and segregation of SnO₂ on the surface of Ga₂O₃(Sn) grains. Full article

(This article belongs to the Special Issue Nano Devices and Nano Sensors)

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13 pages, 1686 KiB

Open AccessArticle

Optimized Planar Microwave Antenna for Nitrogen Vacancy Center Based Sensing Applications

by Oliver Roman Opaluch, Nimba Oshnik, Richard Nelz and Elke Neu

Nanomaterials 2021, 11(8), 2108; https://doi.org/10.3390/nano11082108 - 19 Aug 2021

Cited by 18 | Viewed by 7626

Abstract

Individual nitrogen vacancy (NV) color centers in diamond are versatile, spin-based quantum sensors. Coherently controlling the spin of NV centers using microwaves in a typical frequency range between 2.5 and 3.5 GHz is necessary for sensing applications. In this work, we present a [...] Read more.

Individual nitrogen vacancy (NV) color centers in diamond are versatile, spin-based quantum sensors. Coherently controlling the spin of NV centers using microwaves in a typical frequency range between 2.5 and 3.5 GHz is necessary for sensing applications. In this work, we present a stripline-based, planar,

Ω

-shaped microwave antenna that enables one to reliably manipulate NV spins. We found an optimal antenna design using finite integral simulations. We fabricated our antennas on low-cost, transparent glass substrate. We created highly uniform microwave fields in areas of roughly 400 × 400 μm² while realizing high Rabi frequencies of up to 10 MHz in an ensemble of NV centers. Full article

(This article belongs to the Special Issue Nano Devices and Nano Sensors)

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10 pages, 2654 KiB

Open AccessArticle

Size-Dependent Electroluminescence and Current-Voltage Measurements of Blue InGaN/GaN µLEDs down to the Submicron Scale

by Stefan Wolter, Hendrik Spende, Jan Gülink, Jana Hartmann, Hergo-Heinrich Wehmann, Andreas Waag, Andreas Lex, Adrian Avramescu, Hans-Jürgen Lugauer, Norwin von Malm, Jean-Jacques Drolet and Martin Strassburg

Nanomaterials 2021, 11(4), 836; https://doi.org/10.3390/nano11040836 - 25 Mar 2021

Cited by 21 | Viewed by 3575

Abstract

Besides high-power light-emitting diodes (LEDs) with dimensions in the range of mm, micro-LEDs (μLEDs) are increasingly gaining interest today, motivated by the future applications of μLEDs in augmented reality displays or for nanometrology and sensor technology. A key aspect of this miniaturization is [...] Read more.

Besides high-power light-emitting diodes (LEDs) with dimensions in the range of mm, micro-LEDs (μLEDs) are increasingly gaining interest today, motivated by the future applications of μLEDs in augmented reality displays or for nanometrology and sensor technology. A key aspect of this miniaturization is the influence of the structure size on the electrical and optical properties of μLEDs. Thus, in this article, investigations of the size dependence of the electro-optical properties of μLEDs, with diameters in the range of 20 to 0.65 μm, by current–voltage and electroluminescence measurements are described. The measurements indicated that with decreasing size leakage currents in the forward direction decrease. To take advantage of these benefits, the surface has to be treated properly, as otherwise sidewall damages induced by dry etching will impair the optical properties. A possible countermeasure is surface treatment with a potassium hydroxide based solution that can reduce such defects. Full article

(This article belongs to the Special Issue Nano Devices and Nano Sensors)

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12 pages, 5281 KiB

Open AccessArticle

Field Emission Air-Channel Devices as a Voltage Adder

by Wen-Teng Chang, Ming-Chih Cheng, Tsung-Ying Chuang and Ming-Yen Tsai

Nanomaterials 2020, 10(12), 2378; https://doi.org/10.3390/nano10122378 - 29 Nov 2020

Cited by 9 | Viewed by 2275

Abstract

Field emission air-channel (FEAC) devices can work under atmospheric pressure with a low operation voltage when the electron channel is far less than the mean free path (MFP) in the air, thereby making them a practical component in circuits. Forward and reverse electron [...] Read more.

Field emission air-channel (FEAC) devices can work under atmospheric pressure with a low operation voltage when the electron channel is far less than the mean free path (MFP) in the air, thereby making them a practical component in circuits. Forward and reverse electron emissions of the current FEAC devices demonstrated symmetric Fowler–Nordheim (F–N) plots owing to the symmetric cathode and anode electrodes. This research aimed to demonstrate the arithmetic application of the FEAC devices, their substrate effect, and reliability. A voltage adder was composed of two FEAC devices whose two inputs were connected to two separate function generators, and one output was wire-connected to an oscilloscope. The devices were on a thin dielectric film and low-resistivity silicon substrate to evaluate the parasitic components and substrate effect, resulting in frequency-dependent impedance. The results show that the FEAC devices possessed arithmetic function, but the output voltage decreased. The FEAC devices were still capable of serving as a voltage adder after the reliability test, but electric current leakage increased. Finite element analysis indicated that the highest electrical fields and electron trajectories occur at the apices where the electrons travel with the shortest route less than the MFP in the air, thereby meeting the FEAC devices’ design. The modeling also showed that a sharp apex would generate a high electric field at the tip-gap-tip, enhancing the tunneling current. Full article

(This article belongs to the Special Issue Nano Devices and Nano Sensors)

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19 pages, 3380 KiB

Open AccessArticle

Nanostructure ITO and Get More of It. Better Performance at Lower Cost

by Manel López, Juan Luis Frieiro, Miquel Nuez-Martínez, Martí Pedemonte, Francisco Palacio and Francesc Teixidor

Nanomaterials 2020, 10(10), 1974; https://doi.org/10.3390/nano10101974 - 5 Oct 2020

Cited by 7 | Viewed by 2920

Abstract

In this paper, we investigated how different growth conditions (i.e., temperature, growth time, and composition) allows for trading off cost (i.e., In content) and performance of nanostructured indium tin oxide (ITO) for biosensing applications. Next, we compared the behavior of these functionalized nanostructured [...] Read more.

In this paper, we investigated how different growth conditions (i.e., temperature, growth time, and composition) allows for trading off cost (i.e., In content) and performance of nanostructured indium tin oxide (ITO) for biosensing applications. Next, we compared the behavior of these functionalized nanostructured surfaces obtained in different growth conditions between each other and with a standard thin film as a reference, observing improvements in effective detection area up to two orders of magnitude. This enhanced the biosensor’s sensitivity, with higher detection level, better accuracy and higher reproducibility. Results show that below 150 °C, the growth of ITO over the substrate forms a homogenous layer without any kind of nanostructuration. In contrast, at temperatures higher than 150 °C, a two-phase temperature-dependent growth was observed. We concluded that (i) nanowire length grows exponentially with temperature (activation energy 356 meV) and leads to optimal conditions in terms of both electroactive surface area and sensitivity at around 300 °C, (ii) longer times of growth than 30 min lead to larger active areas and (iii) the In content in a nanostructured film can be reduced by 10%, obtaining performances equivalent to those found in commercial flat-film ITO electrodes. In summary, this work shows how to produce appropriate materials with optimized cost and performances for different applications in biosensing. Full article

(This article belongs to the Special Issue Nano Devices and Nano Sensors)

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10 pages, 8104 KiB

Open AccessArticle

Silicon Waveguide Integrated with Germanium Photodetector for a Photonic-Integrated FBG Interrogator

by Hongqiang Li, Sai Zhang, Zhen Zhang, Shasha Zuo, Shanshan Zhang, Yaqiang Sun, Ding Zhao and Zanyun Zhang

Nanomaterials 2020, 10(9), 1683; https://doi.org/10.3390/nano10091683 - 27 Aug 2020

Cited by 19 | Viewed by 5220

Abstract

We report a vertically coupled germanium (Ge) waveguide detector integrated on silicon-on-insulator waveguides and an optimized device structure through the analysis of the optical field distribution and absorption efficiency of the device. The photodetector we designed is manufactured by IMEC, and the tests [...] Read more.

We report a vertically coupled germanium (Ge) waveguide detector integrated on silicon-on-insulator waveguides and an optimized device structure through the analysis of the optical field distribution and absorption efficiency of the device. The photodetector we designed is manufactured by IMEC, and the tests show that the device has good performance. This study theoretically and experimentally explains the structure of Ge PIN and the effect of the photodetector (PD) waveguide parameters on the performance of the device. Simulation and optimization of waveguide detectors with different structures are carried out. The device’s structure, quantum efficiency, spectral response, response current, changes with incident light strength, and dark current of PIN-type Ge waveguide detector are calculated. The test results show that approximately 90% of the light is absorbed by a Ge waveguide with 20 μm Ge length and 500 nm Ge thickness. The quantum efficiency of the PD can reach 90.63%. Under the reverse bias of 1 V, 2 V and 3 V, the detector’s average responsiveness in C-band reached 1.02 A/W, 1.09 A/W and 1.16 A/W and the response time is 200 ns. The dark current is only 3.7 nA at the reverse bias voltage of −1 V. The proposed silicon-based Ge PIN PD is beneficial to the integration of the detector array for photonic integrated arrayed waveguide grating (AWG)-based fiber Bragg grating (FBG) interrogators. Full article

(This article belongs to the Special Issue Nano Devices and Nano Sensors)

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16 pages, 6408 KiB

Open AccessArticle

The Structural, Electronic, and Optical Properties of Ge/Si Quantum Wells: Lasing at a Wavelength of 1550 nm

by Hongqiang Li, Jianing Wang, Jinjun Bai, Shanshan Zhang, Sai Zhang, Yaqiang Sun, Qianzhi Dou, Mingjun Ding, Youxi Wang, Dan Qu, Jilin Du, Chunxiao Tang, Enbang Li and Joan Daniel Prades

Nanomaterials 2020, 10(5), 1006; https://doi.org/10.3390/nano10051006 - 25 May 2020

Cited by 2 | Viewed by 4187

Abstract

The realization of a fully integrated group IV electrically driven laser at room temperature is an essential issue to be solved. We introduced a novel group IV side-emitting laser at a wavelength of 1550 nm based on a 3-layer Ge/Si quantum well (QW). [...] Read more.

The realization of a fully integrated group IV electrically driven laser at room temperature is an essential issue to be solved. We introduced a novel group IV side-emitting laser at a wavelength of 1550 nm based on a 3-layer Ge/Si quantum well (QW). By designing this scheme, we showed that the structural, electronic, and optical properties are excited for lasing at 1550 nm. The preliminary results show that the device can produce a good light spot shape convenient for direct coupling with the waveguide and single-mode light emission. The laser luminous power can reach up to 2.32 mW at a wavelength of 1550 nm with a 300-mA current. Moreover, at room temperature (300 K), the laser can maintain maximum light power and an ideal wavelength (1550 nm). Thus, this study provides a novel approach to reliable, efficient electrically pumped silicon-based lasers. Full article

(This article belongs to the Special Issue Nano Devices and Nano Sensors)

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Review

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29 pages, 13108 KiB

Open AccessReview

Liquid Metal-Based Devices: Material Properties, Fabrication and Functionalities

by Jian Dong, Yuanyuan Zhu, Zhifu Liu and Meng Wang

Nanomaterials 2021, 11(12), 3400; https://doi.org/10.3390/nano11123400 - 15 Dec 2021

Cited by 13 | Viewed by 4345

Abstract

This paper reviews the material properties, fabrication and functionalities of liquid metal-based devices. In modern wireless communication technology, adaptability and versatility have become attractive features of any communication device. Compared with traditional conductors such as copper, the flow characteristics and lack of elastic [...] Read more.

This paper reviews the material properties, fabrication and functionalities of liquid metal-based devices. In modern wireless communication technology, adaptability and versatility have become attractive features of any communication device. Compared with traditional conductors such as copper, the flow characteristics and lack of elastic limit of conductive fluids make them ideal alternatives for applications such as flexible circuits, soft electronic devices, wearable stretch sensors, and reconfigurable antennas. These fluid properties also allow for innovative manufacturing techniques such as 3-D printing, injecting or spraying conductive fluids on rigid/flexible substrates. Compared with traditional high-frequency switching methods, liquid metal (LM) can easily use micropumps or an electrochemically controlled capillary method to achieve reconfigurability of the device. The movement of LM over a large physical dimension enhances the reconfigurable state of the antenna, without depending on nonlinear materials or mechanisms. When LM is applied to wearable devices and sensors such as electronic skins (e-skins) and strain sensors, it consistently exhibits mechanical fatigue resistance and can maintain good electrical stability under a certain degree of stretching. When LM is used in microwave devices and paired with elastic linings such as polydimethylsiloxane (PDMS), the shape and size of the devices can be changed according to actual needs to meet the requirements of flexibility and a multistate frequency band. In this work, we discuss the material properties, fabrication and functionalities of LM. Full article

(This article belongs to the Special Issue Nano Devices and Nano Sensors)

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