scholarly journals Highly Fast Response of Pd/Ta2O5/SiC and Pd/Ta2O5/Si Schottky Diode-Based Hydrogen Sensors

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1042
Author(s):  
Muhammad Hussain ◽  
Woonyoung Jeong ◽  
Il-Suk Kang ◽  
Kyeong-Keun Choi ◽  
Syed Hassan Abbas Jaffery ◽  
...  
Keyword(s):  
Schottky Diode ◽  
Rf Sputtering ◽  
Fast Response ◽  
Dynamic Responses ◽  
Optimum Operating ◽  
Optimum Operating Temperature ◽  
Si Substrates ◽  
Constant Bias ◽  
Highly Sensitive ◽  
Fast Rise

Herein, the fabrication of a novel highly sensitive and fast hydrogen (H2) gas sensor, based on the Ta2O5 Schottky diode, is described. First, Ta2O5 thin films are deposited on silicon carbide (SiC) and silicon (Si) substrates via a radio frequency (RF) sputtering method. Then, Pd and Ni are respectively deposited on the front and back of the device. The deposited Pd serves as a H2 catalyst, while the Ni functions as an Ohmic contact. The devices are then tested under various concentrations of H2 gas at operating temperatures of 300, 500, and 700 °C. The results indicate that the Pd/Ta2O5 Schottky diode on the SiC substrate exhibits larger concentration and temperature sensitivities than those of the device based on the Si substrate. In addition, the optimum operating temperature of the Pd/Ta2O5 Schottky diode for use in H2 sensing is shown to be about 300 °C. At this optimum temperature, the dynamic responses of the sensors towards various concentrations of H2 gas are then examined under a constant bias current of 1 mA. The results indicate a fast rise time of 7.1 s, and a decay of 18 s, for the sensor based on the SiC substrate.

scholarly journals Synthesis of a Flower-Like g-C3N4/ZnO Hierarchical Structure with Improved CH4 Sensing Properties

Nanomaterials ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 724 ◽  
Author(s):  
Xiaojie Li ◽  
Yanwei Li ◽  
Guang Sun ◽  
Na Luo ◽  
Bo Zhang ◽  
...  
Keyword(s):  
Hierarchical Structure ◽  
Carbon Nitride ◽  
Fast Response ◽  
Optimum Operating ◽  
Optimum Operating Temperature ◽  
Sensing Properties ◽  
Long Term Stability ◽  
Response Recovery ◽  
Calcination Method

In this paper, a hierarchical structure of graphite carbon nitride (g-C3N4) modified ZnO (g-C3N4/ZnO) was synthesized using a simple precipitation-calcination method. Through this method, g-C3N4 nanosheets with a controlled content were successfully decorated on the petals of flower-like ZnO. Various techniques were used to confirm the successful formation of the g-C3N4/ZnO hierarchical structure. The methane (CH4) sensing properties of g-C3N4/ZnO sensor were investigated. The result exhibited that after decorating ZnO with g-C3N4, the CH4 sensing performances of the fabricated sensor were remarkably improved. At the optimum operating temperature of 320 °C, the response of the sensor fabricated with CNZ-3 (the sample with an optimum content of g-C3N4) towards 1000 ppm CH4 was as high as 11.9 (Ra/Rg), which was about 2.2 times higher than that of the pure ZnO sensor (5.3). In addition, the CNZ-3 sensor also exhibited a fast response/recovery speed (15/28 s) and outstanding long-term stability. The enhancing CH4 sensing mechanism may be contributed to enlarged surface area, pore structure, and g-C3N4-ZnO n-n junction.

UNIAXIALLY ALIGNED In2O3 NANOFIBERS BASED SENSORS WITH FAST RESPONSE TO ETHANOL

2012 ◽  
Vol 24 (02) ◽  
pp. 105-109
Author(s):  
Hang Liu ◽  
Hui-Tao Fan ◽  
Xiu-Juan Xu ◽  
Tong Zhang
Keyword(s):  
Magnetic Field ◽  
Operating Temperature ◽  
Average Diameter ◽  
Fast Response ◽  
Optimum Operating ◽  
Optimum Operating Temperature ◽  
Electrospinning Method ◽  
Aligned Nanofibers ◽  
Recovery Times ◽  
Response And Recovery

Uniaxially aligned In2O3 nanofibers are prepared by magnetic-field-assisted electrospinning method. The average diameter of the gained nanofibers is about 90 nm. The optimum operating temperature of the sensor based on the uniaxially aligned In2O3 nanofibers to ethanol is 120°C, the response and recovery times of the sensor are 0.4 s and 3 s, respectively. Compared with the randomly deposited nanofibers, the uniaxially aligned nanofibers show much rapider response.

scholarly journals Study on the Ozone Gas Sensing Properties of Rf-Sputtered Al-Doped NiO Films

2021 ◽  
Vol 11 (7) ◽  
pp. 3104
Author(s):  
Athanasios Paralikis ◽  
Emmaouil Gagaoudakis ◽  
Viktoras Kampitakis ◽  
Elias Aperathitis ◽  
George Kiriakidis ◽  
...  
Keyword(s):  
Oxygen Content ◽  
Room Temperature ◽  
Gas Sensing ◽  
Operating Temperature ◽  
Rf Sputtering ◽  
Optimum Operating ◽  
Optimum Operating Temperature ◽  
Sensing Properties ◽  
Al Content ◽  
Gas Sensing Properties

Al-doped NiO (NiO:Al) has attracted the interest of researchers due to its excellent optical and electrical properties. In this work, NiO:Al films were deposited on glass substrates by the radio frequencies (rf) sputtering technique at room temperature and they were tested against ozone gas. The Oxygen content in (Ar-O2) plasma was varied from 2% to 4% in order to examine its effect on the gas sensing performance of the films. The thickness of the films was between 160.3 nm and 167.5 nm, while the Al content was found to be between 5.3at% and 6.7at%, depending on the oxygen content in plasma. It was found that NiO:Al films grown with 4% O2 in plasma were able to detect 60 ppb of ozone with a sensitivity of 3.18% at room temperature, while the detection limit was further decreased to 10 ppb, with a sensitivity of 2.54%, at 80 °C, which was the optimum operating temperature for these films. In addition, the films prepared in 4% O2 in plasma had lower response and recovery time compared to those grown with lower O2 content in plasma. Finally, the role of the operating temperature on the gas sensing properties of the NiO:Al films was investigated.

Novel optical oxygen sensing by phosphorescence quenching of palladium porphyrin self-assembled film on alumina plate

2000 ◽  
Vol 04 (02) ◽  
pp. 179-184 ◽  
Author(s):  
YUTAKA AMAO ◽  
KEISUKE ASAI ◽  
ICHIRO OKURA
Keyword(s):  
Oxygen Pressure ◽  
Oxygen Sensor ◽  
Response Times ◽  
Oxygen Sensing ◽  
Fast Response ◽  
Phosphorescence Quenching ◽  
Highly Sensitive ◽  
Optical Oxygen Sensor ◽  
Self Assembled ◽  
Quenching By Oxygen

An optical oxygen sensor based on the phosphorescence quenching of palladium tetrakis(4-carboxyphenyl)porphyrin (PdTCPP) self-assembled film (SAM) on alumina plate was developed. The phosphorescence intensity of PdTCPP film decreased with increasing oxygen pressure, indicating that the film can be used as an optical oxygen-sensing device based on phosphorescence quenching by oxygen. The ratio I0/I100 as a sensitivity measure of the sensing film is estimated to be 17.7, showing that the film is a highly sensitive device for oxygen pressure. The film obeyed Stern–Volmer plots with a multisite model and possessed good operational stability and a fast response. Response times are 36 s for deoxygenated to oxygenated conditions and 148 s for the reverse conditions.

Pre-Excitation, Catalytic Oxidation of Analytes over Hopcalite in Flame/Furnace Infrared Emission (FIRE) Spectrometry

1992 ◽  
Vol 46 (4) ◽  
pp. 631-639 ◽  
Author(s):  
Yunke Zhang ◽  
Marianna A. Busch ◽  
Kenneth W. Busch
Keyword(s):  
Detection Limit ◽  
Soot Formation ◽  
Vibrational Excitation ◽  
Infrared Emission ◽  
Optimum Operating ◽  
Air Flow Rate ◽  
Linear Calibration ◽  
Furnace Temperature ◽  
Optimum Operating Temperature ◽  
Pure Acetone

Gas-phase infrared emission measurements made with the use of a new, specially designed, electrically heated furnace or a small hydrogen/air flame have shown that oxidation of a variety of carbon-based analytes to CO2 over the catalyst hopcalite prior to vibrational excitation in the furnace or flame markedly improves the response of the FIRE radiometer. Calibration curves obtained with the use of the furnace alone were generally nonlinear, while those obtained with the flame alone had slopes that were compound dependent. By the use of hopcalite in conjunction with the furnace, conversion to CO2 was significantly improved, and the FIRE response to pure acetone, benzene, dichloromethane, 1-chloro-2-methylpropane, heptane, methanol, and toluene became directly proportional to the number of moles of carbon introduced. In the case of the flame, as little as 0.1 g of hopcalite was sufficient to give a single, linear calibration curve (based on moles of carbon) for injection volumes of 0.2–1.0 μL of a test mixture composed of equal volumes of acetone, benzene, hexane, propanol, and tetrahydrofuran. With the use of hopcalite at its experimentally determined, optimum operating temperature of 380°C, an air flow rate of 45 mL min−1, and a furnace temperature of 600°C, the detection limit for hexane was found to be 518 ng C s−1. The use of hopcalite in conjunction with the flame (900°C) improved this detection limit by two orders of magnitude, due to the combined effects of an increase in excitation temperature and a decrease in source background noise. Injection of chlorinated compounds was found to temporarily poison the hopcalite, resulting in soot formation and loss of catalytic activity for periods of approximately ten minutes.

YBa2Cu3O7 Thin Films on Polycrystalline Diamond Films with Buffer Layers

1992 ◽  
Vol 275 ◽  
Author(s):  
G. Cui ◽  
C. P. Beetz ◽  
B. A. Lincoln ◽  
P. S. Kirlin
Keyword(s):  
Thin Films ◽  
Diamond Films ◽  
Rf Sputtering ◽  
Polycrystalline Diamond ◽  
Fast Response ◽  
Buffer Layers ◽  
Multichip Modules ◽  
Ir Detectors ◽  
Ybco Films ◽  
First Time

ABSTRACTThe deposition of in-situ YBa2CU3O7-δ Superconducting films on polycrystalline diamond thin films has been demonstrated for the first time. Three different composite buffer layer systems have been explored for this purpose: (1) Diamond/Zr/YSZ/YBCO, (2) Diamond/Si3N4/YSZ/YBCO, and (3) Diamond/SiO2/YSZ/YBCO. The Zr was deposited by dc sputtering on the diamond films at 450 to 820 °C. The YSZ was deposited by reactive on-axis rf sputtering at 680 to 750 °C. The Si3N4 and SiO2 were also deposited by on-axis rf sputtering at 400 to 700 °C. YBCO films were grown on the buffer layers by off-axis rf sputtering at substrate temperatures between 690 °C and 750 °C. In all cases, the as-deposited YBCO films were superconducting above 77 K. This demonstration enables the fabrication of low heat capacity, fast response time bolometric IR detectors and paves the way for the use of HTSC on diamond for interconnect layers in multichip modules.

Near Room Temperature, Fast-Response, and Highly Sensitive Triethylamine Sensor Assembled with Au-Loaded ZnO/SnO2Core–Shell Nanorods on Flat Alumina Substrates

2015 ◽  
Vol 7 (34) ◽  
pp. 19163-19171 ◽  
Author(s):  
Dian-Xing Ju ◽  
Hong-Yan Xu ◽  
Zhi-Wen Qiu ◽  
Zi-Chao Zhang ◽  
Qi Xu ◽  
...  
Keyword(s):  
Room Temperature ◽  
Fast Response ◽  
Highly Sensitive

scholarly journals Titanium Dioxide-Based64∘YXLiNbO3Surface Acoustic Wave Hydrogen Gas Sensors

2008 ◽  
Vol 2008 ◽  
pp. 1-5 ◽  
Author(s):  
A. Z. Sadek ◽  
D. Buso ◽  
A. Martucci ◽  
P. Mulvaney ◽  
W. Wlodarski ◽  
...  
Keyword(s):  
Titanium Dioxide ◽  
Acoustic Wave ◽  
Gas Sensors ◽  
Sol Gel ◽  
Hydrogen Gas ◽  
Optimum Operating ◽  
Optimum Operating Temperature ◽  
Helium Atmosphere ◽  
Gas Detectors ◽  
Hydrogen Gas Sensors

Amorphous titanium dioxide (TiO2) and gold (Au) dopedTiO2-based surface acoustic wave (SAW) sensors have been investigated as hydrogen gas detectors. The nanocrystal-dopedTiO2films were synthesized through a sol-gel route, mixing a Ti-butoxide-based solution with diluted colloidal gold nanoparticles. The films were deposited via spin coating onto64∘YXLiNbO3SAW transducers in a helium atmosphere. The SAW gas sensors were operated at various temperatures between 150 and310∘C. It was found that gold doping onTiO2increased the device sensitivity and reduced the optimum operating temperature.

Xylene-sensing of Fe2(MoO4)3 nanoplates prepared via a hydrothermal method

2017 ◽  
Vol 10 (03) ◽  
pp. 1750022 ◽  
Author(s):  
Mengying Xu ◽  
Zhidong Lin ◽  
Wenying Guo ◽  
Yuyuan Hong ◽  
Ping Fu ◽  
...  
Keyword(s):  
Gas Sensors ◽  
Gas Sensing ◽  
Operating Temperature ◽  
Hydrothermal Process ◽  
Optimum Operating ◽  
Average Crystalline Size ◽  
Optimum Operating Temperature ◽  
Recovery Times ◽  
Response And Recovery ◽  
Simple Hydrothermal Process

Fe2(MoO4)3 nanoplates were prepared via a simple hydrothermal process. The average crystalline size of these nanoplates is 85.8[Formula: see text]nm. The sensor based on Fe2(MoO4)3 shows a high gas sensing performance to xylene. The response of Fe2(MoO4)3 sensor is 25.9–100[Formula: see text]ppm xylene at optimum operating temperature of 340[Formula: see text]C. The response and recovery times to 100[Formula: see text]ppm xylene are 4 and 10[Formula: see text]s, respectively. Furthermore, the Fe2(MoO4)3 sensor exhibits remarkable selectivity detection of xylene gas with negligible responses to toluene and benzene. Therefore, the Fe2(MoO4)3 is a promising material for the detection of xylene gas sensors.

scholarly journals A Highly Sensitive and Flexible Capacitive Pressure Sensor Based on a Porous Three-Dimensional PDMS/Microsphere Composite

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1412 ◽  
Author(s):  
Young Jung ◽  
Wookjin Lee ◽  
Kyungkuk Jung ◽  
Byunggeon Park ◽  
Jinhyoung Park ◽  
...  
Keyword(s):  
Pressure Sensor ◽  
Sacrificial Layer ◽  
Three Dimensional ◽  
Pressure Sensors ◽  
Capacitive Pressure Sensor ◽  
Mechanical Stimuli ◽  
Highly Sensitive ◽  
Flexible Pressure Sensors ◽  
Fast Rise ◽  
Better Than

In recent times, polymer-based flexible pressure sensors have been attracting a lot of attention because of their various applications. A highly sensitive and flexible sensor is suggested, capable of being attached to the human body, based on a three-dimensional dielectric elastomeric structure of polydimethylsiloxane (PDMS) and microsphere composite. This sensor has maximal porosity due to macropores created by sacrificial layer grains and micropores generated by microspheres pre-mixed with PDMS, allowing it to operate at a wider pressure range (~150 kPa) while maintaining a sensitivity (of 0.124 kPa−1 in a range of 0~15 kPa) better than in previous studies. The maximized pores can cause deformation in the structure, allowing for the detection of small changes in pressure. In addition to exhibiting a fast rise time (~167 ms) and fall time (~117 ms), as well as excellent reproducibility, the fabricated pressure sensor exhibits reliability in its response to repeated mechanical stimuli (2.5 kPa, 1000 cycles). As an application, we develop a wearable device for monitoring repeated tiny motions, such as the pulse on the human neck and swallowing at the Adam’s apple. This sensory device is also used to detect movements in the index finger and to monitor an insole system in real-time.

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