Improved Long‐Term Stability and Reduced Humidity Effect in Gas Sensing: SiO<sub>2</sub> Ultra‐Thin Layered ZnO Columnar Films

Postica, Vasile; Lupan, Oleg; Gapeeva, Anna; Hansen, Luka; Khaledialidusti, Rasoul; Mishra, Abhishek Kumar; Drewes, Jonas; Kersten, Holger; Faupel, Franz; Adelung, Rainer; Hansen, Sandra

doi:10.1002/admt.202001137

Cited by 33 publications

(17 citation statements)

References 71 publications

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“…Figure S9 shows that the current–voltage characteristics show ohmic character at room temperature and operating temperatures of 150 and 200 °C. The I – V electrical curve changes at elevated operating temperatures between 250 and 350 °C, demonstrating the nonlinear behavior of the sensor due to an increase of its conductivity. − It was also observed that the electrical current values are quite small, on the order of microamperes, up to the operating temperature of 200 °C. However, the value of the electrical current increases in the order of milliamperes after raising the operating temperature from 250 to 350 °C because of the increase in electrical conductivity. ,, …”

Section: Resultsmentioning

confidence: 94%

Al₂O₃/ZnO Heterostructure-Based Sensors for Volatile Organic Compounds in Safety Applications

Lupan

Santos‐Carballal

Magariu

et al. 2022

ACS Appl. Mater. Interfaces

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Monitoring volatile organic compounds (VOCs) in harsh environments, especially for safety applications, is a growing field that requires specialized sensor structures. In this work, we demonstrate the sensing properties toward the most common VOCs of columnar Al2O3/ZnO heterolayer-based sensors. We have also developed an approach to tune the sensor selectivity by changing the thickness of the exposed amorphous Al2O3 layer from 5 to 18 nm. Columnar ZnO films are prepared by a chemical solution method, where the exposed surface is decorated with an Al2O3 nanolayer via thermal atomic layer deposition at 75 °C. We have investigated the structure and morphology as well as the vibrational, chemical, electronic, and sensor properties of the Al2O3/ZnO heterostructures. Transmission electron microscopy (TEM) studies show that the upper layers consist of amorphous Al2O3 films. The heterostructures showed selectivity to 2-propanol vapors only within the range of 12–15 nm thicknesses of Al2O3, with the highest response value of ∼2000% reported for a thickness of 15 nm at the optimal working temperature of 350 °C. Density functional theory (DFT) calculations of the Al2O3/ZnO(100) interface and its interaction with 2-propanol (2-C3H7OH), n-butanol (n-C4H9OH), ethanol (C2H5OH), acetone (CH3COCH3), hydrogen (H2), and ammonia (NH3) show that the molecular affinity for the Al2O3/ZnO(100) interface decreases from 2-propanol (2-C3H7OH) ≈ n-butanol (n-C4H9OH) > ethanol (C2H5OH) > acetone (CH3COCH3) > hydrogen (H2), which is consistent with our gas response experiments for the VOCs. Charge transfers between the surface and the adsorbates, and local densities of states of the interacting atoms, support the calculated strength of the molecular preferences. Our findings are highly important for the development of 2-propanol sensors and to our understanding of the effect of the heterojunction and the thickness of the top nanolayer on the gas response, which thus far have not been reported in the literature.

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Section: Resultsmentioning

confidence: 94%

Al₂O₃/ZnO Heterostructure-Based Sensors for Volatile Organic Compounds in Safety Applications

Lupan

Santos‐Carballal

Magariu

et al. 2022

ACS Appl. Mater. Interfaces

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“…Meanwhile, the H2O on the surface of the sensing film, When the testing chamber contained a certain amount of n-butanol by injection, the chemisorbed oxygen ions and their derivatives on the surface of the sensing materials would react with the gas molecules of the n-butanol, and then caused the backdonation of the trapped electrons to the depletion layers, resulting in the decrease in the sensor resistance due to the reduction in the range of depletion region and the height of the barriers between the nanobelts [56,57]. Meanwhile, the H 2 O on the surface of the sensing film, one of the byproducts in the reaction described above, would further decrease the resistivity of the sensor [58]. Regarding the enhanced gas-sensing property of 0.61 at% Pb-doped ZnO porous nanobelts, it is worth noting that the gas-sensing process of pristine ZnO porous nanobelts was short of the sufficient adsorbed oxygen molecules and oxygen vacancies generated from the dopant of Pb.…”

Section: Sensing Mechanismmentioning

confidence: 99%

Porous Pb-Doped ZnO Nanobelts with Enriched Oxygen Vacancies: Preparation and Their Chemiresistive Sensing Performance

2022

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Among various approaches to improve the sensing performance of metal oxide, the metal-doped method is perceived as effective, and has received great attention and is widely investigated. However, it is still a challenge to construct heterogeneous metal-doped metal oxide with an excellent sensing performance. In the present study, porous Pb-doped ZnO nanobelts were prepared by a simply partial cation exchange method, followed by in situ thermal oxidation. Detailed characterization confirmed that Pb was uniformly distributed on porous nanobelts. Additionally, it occupied the Zn situation, not forming its oxides. The gas-sensing measurements revealed that 0.61 at% Pb-doped ZnO porous nanobelts exhibited a selectively enhanced response with long-term stability toward n-butanol among the investigated VOCs. The relative response to 50 ppm of n-butanol was up to 47.7 at the working temperature of 300 °C. Additionally, the response time was short (about 5 s). These results were mainly ascribed to the porous nanostructure, two-dimensional belt-like morphology, enriched oxygen vacancies and the specific synergistic effect from the Pb dopant. Finally, a possible sensing mechanism of porous Pb-doped ZnO nanobelts is proposed and discussed.

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“…It is evident from Figure 11b that the aluminum-doped ZnO reduced the sensing response from 50 to 30 %, however, the nickel-doped ZnO maintained the sensing response and finally, the pure ZnO showed a slight increase in the sensing response, as previously reported by Bie et al [81] The causes of fluctuation have been researched beforehand, these can be humidity, temperature, and surface contaminations from the atmosphere. [82,83] The discrepancies in the sensing responses are due to the surface oxidation or reduction mechanics of the ZnO surface. Further detailed analysis with respect to time is necessary to understand the stability properties of ZnO sensors.…”

Section: Co 2 Gas Sensing Propertiesmentioning

confidence: 99%

Carbon Dioxide Detectors based on Al‐ and Ni‐Doped ZnO

Lozano-Rosas

Hernandez

Elizalde-González

et al. 2022

Physica Status Solidi (a)

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Humanity all around the world currently faces two serious challenges: global warming and the COVID-19 pandemic. It is well known that the earth's atmosphere is composed of greenhouse gases that act as a shielding blanket, keeping the global temperature in an optimal range. [1] The three main greenhouse gasses which have presented a significant increment in the course of the industrial period are carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O). [2] CO 2 plays a primary role in global warming because of its production due to a wide range of sources like manufacturing processes, automobiles, human respiration, decomposition, ocean release, etc. [3] In contrast, from December 2019 to date, the COVID-19 pandemic is causing a global impact on every sector of society. [4] One of the strategies of mitigation for the pandemic has been CO 2 concentration monitoring in enclosed spaces to measure indoor ventilation requirements and thus reduce the risk of contagion by the aerosol transmission of the virus. Also, it is clear that CO 2 monitoring has become mandatory to maintain air quality.The values of CO 2 concentration in outdoor ambient air are %400 ppm. [5] Regarding CO 2 concentrations in internal environments, the reality is different depending on the country, specific location, and ventilation system; however, according to the document "Recommendations for operation and maintenance of air conditioning and ventilation systems of buildings and premises for the prevention of the spread of SARS-Cov-2" from Spanish Ministry of Health, for good quality air, it is considered that the concentration of CO 2 in the indoor environment with respect to its concentration in the outdoor environment, should not be higher than 500 ppm. [6] ðCO 2 indoor À CO 2 outdoorÞ < 500 ppm CO 2(1)The first decade of the 21 st century was witness to massive production of sensors, [7] driven principally by the growing concern of global warming. However, new sensing technologies were emerged in the past decade, such as calorimetric sensors (CB), metal-oxide-semiconductor field-effect transistor (MOSFET), conducting polymer sensors, electrochemical sensors (EC), metal-oxide semiconductor (MOS), optical sensors, quartz crystal microbalance (QMB), and surface acoustic wave (SAW). [8] Among these, MOS sensors are mostly investigated, due to their excellent sensitivity, very short response times, low cost, minimal noise, small size, low power consumption for adequate battery life, detection of both oxidizing and reducing gases, easy fabrication, and are excellent candidates for miniaturization with high portability. [9][10][11] There is a wide variety of metal oxides employed for CO 2 detection, including pristine materials:

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Improved Long‐Term Stability and Reduced Humidity Effect in Gas Sensing: SiO₂ Ultra‐Thin Layered ZnO Columnar Films

Cited by 33 publications

References 71 publications

Al₂O₃/ZnO Heterostructure-Based Sensors for Volatile Organic Compounds in Safety Applications

Al₂O₃/ZnO Heterostructure-Based Sensors for Volatile Organic Compounds in Safety Applications

Porous Pb-Doped ZnO Nanobelts with Enriched Oxygen Vacancies: Preparation and Their Chemiresistive Sensing Performance

Carbon Dioxide Detectors based on Al‐ and Ni‐Doped ZnO

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Improved Long‐Term Stability and Reduced Humidity Effect in Gas Sensing: SiO2 Ultra‐Thin Layered ZnO Columnar Films

Cited by 33 publications

References 71 publications

Al2O3/ZnO Heterostructure-Based Sensors for Volatile Organic Compounds in Safety Applications

Al2O3/ZnO Heterostructure-Based Sensors for Volatile Organic Compounds in Safety Applications

Porous Pb-Doped ZnO Nanobelts with Enriched Oxygen Vacancies: Preparation and Their Chemiresistive Sensing Performance

Carbon Dioxide Detectors based on Al‐ and Ni‐Doped ZnO

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Product

Resources

About

Improved Long‐Term Stability and Reduced Humidity Effect in Gas Sensing: SiO₂ Ultra‐Thin Layered ZnO Columnar Films

Al₂O₃/ZnO Heterostructure-Based Sensors for Volatile Organic Compounds in Safety Applications

Al₂O₃/ZnO Heterostructure-Based Sensors for Volatile Organic Compounds in Safety Applications