scholarly journals Measuring Hydrogen in Indoor Air with a Selective Metal Oxide Semiconductor Sensor

Atmosphere ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 366
Author(s):  
Caroline Schultealbert ◽  
Johannes Amann ◽  
Tobias Baur ◽  
Andreas Schütze
Keyword(s):  
Metal Oxide ◽  
Indoor Air ◽  
Metal Oxide Semiconductor ◽  
Oxide Semiconductor ◽  
Relevant Parameter ◽  
Human Presence ◽  
Reference Device ◽  
Total Volatile Organic Compounds ◽  
And Training ◽  
Severe Disturbance

Hydrogen is a ubiquitous but often neglected gas. In analytical measurements hydrogen—as a harmless gas—often is not considered so no studies on hydrogen in indoor air can be found. For metal oxide semiconductor (MOS) gas sensors that are increasingly pushed into the application as TVOC (total volatile organic compounds) sensors, hydrogen is a severe disturbance. On the other hand, hydrogen can be an intentional choice as indicator for human presence similar to carbon dioxide. We present a field-study on hydrogen in indoor air using selective MOS sensors accompanied by an analytical reference device for hydrogen with an accuracy of 10 ppb. Selectivity is achieved by siloxane treatment combined with temperature cycled operation and training with a complex lab calibration using randomized gas mixtures, yielding an uncertainty of 40–60 ppb. The feasibility is demonstrated by release tests with several gases inside a room and by comparison to the reference device. The results show that selective MOS sensors can function as cheap and available hydrogen detectors. Fluctuations in hydrogen concentration without human presence are measured over several days to gain insight in this highly relevant parameter for indoor air quality. The results indicate that the topic needs further attention and that the usage of hydrogen as indicator for human presence might be precluded by other sources and fluctuations.

scholarly journals Field Study of Metal Oxide Semiconductor Gas Sensors in Temperature Cycled Operation for Selective VOC Monitoring in Indoor Air

Atmosphere ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 647
Author(s):  
Tobias Baur ◽  
Johannes Amann ◽  
Caroline Schultealbert ◽  
Andreas Schütze
Keyword(s):  
Air Quality ◽  
Metal Oxide ◽  
Gas Sensor ◽  
Gas Sensors ◽  
Indoor Air ◽  
Ambient Air ◽  
Quantitative Agreement ◽  
Metal Oxide Semiconductor ◽  
Oxide Semiconductor ◽  
High Temporal Resolution

More and more metal oxide semiconductor (MOS) gas sensors with digital interfaces are entering the market for indoor air quality (IAQ) monitoring. These sensors are intended to measure volatile organic compounds (VOCs) in indoor air, an important air quality factor. However, their standard operating mode often does not make full use of their true capabilities. More sophisticated operation modes, extensive calibration and advanced data evaluation can significantly improve VOC measurements and, furthermore, achieve selective measurements of single gases or at least types of VOCs. This study provides an overview of the potential and limits of MOS gas sensors for IAQ monitoring using temperature cycled operation (TCO), calibration with randomized exposure and data-based models trained with advanced machine learning. After lab calibration, a commercial digital gas sensor with four different gas-sensitive layers was tested in the field over several weeks. In addition to monitoring normal ambient air, release tests were performed with compounds that were included in the lab calibration, but also with additional VOCs. The tests were accompanied by different analytical systems (GC-MS with Tenax sampling, mobile GC-PID and GC-RCP). The results show quantitative agreement between analytical systems and the MOS gas sensor system. The study shows that MOS sensors are highly suitable for determining the overall VOC concentrations with high temporal resolution and, with some restrictions, also for selective measurements of individual components.

Suppression of Timing Variations due to Random Dopant Fluctuation by Back-Gate Bias in a Nanometer CMOS Inverter

2020 ◽  
Vol 13 ◽  
Author(s):  
Kai Zhang ◽  
Weifeng Lü ◽  
Peng Si ◽  
Zhifeng Zhao ◽  
Tianyu Yu
Keyword(s):  
Monte Carlo ◽  
Integrated Circuits ◽  
Metal Oxide ◽  
Metal Oxide Semiconductor ◽  
Oxide Semiconductor ◽  
Gate Bias ◽  
Cmos Inverter ◽  
Back Gate ◽  
Random Dopant Fluctuation ◽  
Random Dopant

Background: In state-of-the-art nanometer metal-oxide-semiconductor-field-effect- transistors (MOSFETs), optimization of timing characteristic is one of the major concerns in the design of modern digital integrated circuits. Objective: This study proposes an effective back-gate-biasing technique to comprehensively investigate the timing and its variation due to random dopant fluctuation (RDF) employing Monte Carlo methodology. Methods: To analyze RDF-induced timing variation in a 22-nm complementary metal-oxide semiconductor (CMOS) inverter, an ensemble of 1000 different samples of channel-doping for negative metal-oxide semiconductor (NMOS) and positive metal-oxide semiconductor (PMOS) was reproduced and the input/output curves were measured. Since back-gate bias is technology dependent, we present in parallel results with and without VBG. Results: It is found that the suppression of RDF-induced timing variations can be achieved by appropriately adopting back-gate voltage (VBG) through measurements and detailed Monte Carlo simulations. Consequently, the timing parameters and their variations are reduced and, moreover, that they are also insensitive to channel doping with back-gate bias. Conclusion: Circuit designers can appropriately use back-gate bias to minimize timing variations and improve the performance of CMOS integrated circuits.

Optimized Al-doped TiO2 gate insulator for metal-oxide-semiconductor capacitor on Ge substrate

2021 ◽  
Author(s):  
Dong Gun Kim ◽  
Cheol Hyun An ◽  
Sanghyeon Kim ◽  
Dae Seon Kwon ◽  
Junil Lim ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Leakage Current ◽  
Tio2 Film ◽  
Single Layer ◽  
Atomic Layer ◽  
Metal Oxide Semiconductor ◽  
Gate Insulator ◽  
Oxide Semiconductor ◽  
High K ◽  
Metal Oxide Semiconductor Capacitor

Atomic layer deposited TiO2- and Al2O3-based high-k gate insulator (GI) were examined for the Ge-based metal-oxide-semiconductor capacitor application. The single-layer TiO2 film showed a too high leakage current to be...

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