Numerical Analysis of Oxygen Vacancy Distribution in Semiconductor Gas Sensors in the Cooling Process Based on the Model of Gradient-Distributed Oxygen Vacancies

The oxygen vacancies (VO) play an essential role in the gas-sensing mechanism of semiconductor devices. A diffusion equation is established to describe the VO behaviors during a cooling process based on the model of gradient-distributed oxygen vacancies. Numerical solutions of the diffusion equation are found to illustrate the VO distribution in grains. The gradient of VO distribution is of negative dependence on the cooling rate, which also influences the average VO density in the depletion layer. The migration of oxygen vacancies in cooling process could be interrupted by quenching and it is restarted by the re-annealing process. The VO distributing process is illustrated by three stages from initial uniform distribution to final gradient profile via a transient stage. The influence of VO distribution on gas-sensing characteristics of semiconductor grains is discussed. Potential opportunities are found to control the gas sensor characteristics by a designed annealing process.

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Influence of Oxygen Vacancy Behaviors in Cooling Process on Semiconductor Gas Sensors: A Numerical Analysis

Sensors ◽

10.3390/s18113929 ◽

2018 ◽

Vol 18 (11) ◽

pp. 3929 ◽

Cited By ~ 7

Author(s):

Jianqiao Liu ◽

Wanqiu Wang ◽

Zhaoxia Zhai ◽

Guohua Jin ◽

Yuzhen Chen ◽

...

Keyword(s):

Numerical Analysis ◽

Oxygen Vacancy ◽

Diffusion Equation ◽

Gas Sensors ◽

Gas Sensing ◽

Cooling Process ◽

Proposed Model ◽

Vacancy Model ◽

Vacancy Distribution ◽

Semiconductor Gas Sensors

The influence of oxygen vacancy behaviors during a cooling process in semiconductor gas sensors is discussed by the numerical analysis method based on the gradient-distributed oxygen vacancy model. A diffusion equation is established to describe the behaviors of oxygen vacancies, which follows the effects of diffusion and exclusion in the cooling process. Numerical analysis is introduced to find the accurate solutions of the diffusion equation. The solutions illustrate the oxygen vacancy distribution profiles, which are dependent on the cooling rate as well as the temperature interval of the cooling process. The gas-sensing characteristics of reduced resistance and response are calculated. Both of them, together with oxygen vacancy distribution, show the grain size effects and the re-annealing effect. It is found that the properties of gas sensors can be controlled or adjusted by the designed cooling process. The proposed model provides a possibility for sensor characteristics simulations, which may be beneficial for the design of gas sensors. A quantitative interpretation on the gas-sensing mechanism of semiconductors has been contributed.

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Time-dependent oxygen vacancy distribution and gas sensing characteristics of tin oxide gas sensitive thin films

Sensors and Actuators B Chemical ◽

10.1016/j.snb.2010.06.065 ◽

2010 ◽

Vol 150 (1) ◽

pp. 330-338 ◽

Cited By ~ 24

Author(s):

Jianqiao Liu ◽

Shuping Gong ◽

Qiuyun Fu ◽

Yi Wang ◽

Lin Quan ◽

...

Keyword(s):

Thin Films ◽

Oxygen Vacancy ◽

Tin Oxide ◽

Gas Sensing ◽

Time Dependent ◽

Vacancy Distribution ◽

Sensing Characteristics

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Inhomogeneous Oxygen Vacancy Distribution in Semiconductor Gas Sensors: Formation, Migration and Determination on Gas Sensing Characteristics

Sensors ◽

10.3390/s17081852 ◽

2017 ◽

Vol 17 (8) ◽

pp. 1852 ◽

Cited By ~ 14

Author(s):

Jianqiao Liu ◽

Yinglin Gao ◽

Xu Wu ◽

Guohua Jin ◽

Zhaoxia Zhai ◽

...

Keyword(s):

Oxygen Vacancy ◽

Gas Sensors ◽

Gas Sensing ◽

Vacancy Distribution ◽

Semiconductor Gas Sensors ◽

Sensing Characteristics

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Some Accurate Numerical Solutions of the Soil-Water Diffusion Equation

Soil Science Society of America Journal ◽

10.2136/sssaj1980.03615995004400030047x ◽

1980 ◽

Vol 44 (3) ◽

pp. 656-658 ◽

Cited By ~ 9

Author(s):

R. D. Braddock ◽

J.-Y. Parlange

Keyword(s):

Diffusion Equation ◽

Soil Water ◽

Numerical Solutions ◽

Water Diffusion

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Mesoporous ZnO nanosheets with rich surface oxygen vacancies for UV-activated methane gas sensing at room temperature

Sensors and Actuators B Chemical ◽

10.1016/j.snb.2021.129547 ◽

2021 ◽

Vol 333 ◽

pp. 129547

Author(s):

Jing Wang ◽

Chenyu Hu ◽

Yi Xia ◽

Bo Zhang

Keyword(s):

Room Temperature ◽

Oxygen Vacancies ◽

Gas Sensing ◽

Surface Oxygen ◽

Methane Gas ◽

Zno Nanosheets ◽

Mesoporous Zno

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Transforming Pt-SnO2 Nanoparticles into Pt-SnO2 Composite Nanoceramics for Room-Temperature Hydrogen-Sensing Applications

Materials ◽

10.3390/ma14092123 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2123

Author(s):

Ming Liu ◽

Caochuang Wang ◽

Pengcheng Li ◽

Liang Cheng ◽

Yongming Hu ◽

...

Keyword(s):

Room Temperature ◽

Gas Sensing ◽

Sintering Temperature ◽

Sno2 Nanoparticles ◽

Hydrogen Sensing ◽

Sensing Applications ◽

Nanostructured Metal Oxides ◽

Low Dimensional ◽

Sensing Characteristics ◽

Nanostructured Metal

Many low-dimensional nanostructured metal oxides (MOXs) with impressive room-temperature gas-sensing characteristics have been synthesized, yet transforming them into relatively robust bulk materials has been quite neglected. Pt-decorated SnO2 nanoparticles with 0.25–2.5 wt% Pt were prepared, and highly attractive room-temperature hydrogen-sensing characteristics were observed for them all through pressing them into pellets. Some pressed pellets were further sintered over a wide temperature range of 600–1200 °C. Though the room-temperature hydrogen-sensing characteristics were greatly degraded in many samples after sintering, those samples with 0.25 wt% Pt and sintered at 800 °C exhibited impressive room-temperature hydrogen-sensing characteristics comparable to those of their counterparts of as-pressed pellets. The variation of room-temperature hydrogen-sensing characteristics among the samples was explained by the facts that the connectivity between SnO2 grains increases with increasing sintering temperature, and Pt promotes oxidation of SnO2 at high temperatures. These results clearly demonstrate that some low-dimensional MOX nanocrystals can be successfully transformed into bulk MOXs with improved robustness and comparable room-temperature gas-sensing characteristics.

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