Selective photoactive gas detection of CO and HCHO using highly porous SnO2 and SnO2@TiO2 heterostructure

Herein, a controlled porous structure for photoactive gas sensors was fabricated using the gas-flow thermal evaporation and atomic layer deposition method. To control the porosity of the SnO2 matrix, Ar was introduced to the chamber to adjust the pressure from 0.1 to 1 Torr during thermal evaporatio...

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Published in:Sensors and actuators. B, Chemical Chemical, 2022-05, Vol.358, p.131486, Article 131486
Main Authors: Kim, Sungjin, Cho, Deok-Hyun, Chang, Hyeon-Kyung, Lee, Ho-Nyun, Kim, Hyun-Jong, Park, Tae Joo, Park, Young Min
Format: Article
Language:English
Subjects:
Atomic layer deposition
Atomic layer epitaxy
Carbon monoxide
Conduction bands
Electron transport
Energy levels
Evaporation
Formaldehyde
Gas flow
Gas sensors
Gases
Heterostructures
Oxidation
Photoactive gas sensors
Porosity
Porous heterostructure
Response rates
Response time
Selectivity
Sensors
Target detection
Thermal evaporation
Tin dioxide
Titanium dioxide
Ultraviolet radiation
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Summary:Herein, a controlled porous structure for photoactive gas sensors was fabricated using the gas-flow thermal evaporation and atomic layer deposition method. To control the porosity of the SnO2 matrix, Ar was introduced to the chamber to adjust the pressure from 0.1 to 1 Torr during thermal evaporation. Furthermore, nanoscale TiO2 layers were conformally deposited on the surface of porous SnO2 by atomic layer deposition as a selective active layer for HCHO. As a result, the sensor deposited at a pressure of 0.2 Torr showed high sensitivity and a relatively fast response than other deposition pressures owing to the optimized porosity and better electron transport. The nanoporous structure of SnO2 showed a high response rate of 56.7% when exposed to CO with a concentration of 50 ppm and a low detection limit of 1 ppm. The introduction of a TiO2 layer on the nanoporous SnO2 allowed selective response to HCHO with a response rate of 20% at 10 ppm when the oxidation level of the target gas was well aligned with the state of reactive oxygen of materials under UV irradiation. Furthermore, the sensing capabilities of the SnO2 and SnO2@TiO2 heterostructures, such as the response rate and response time, were assessed at different deposition pressures. Our results clearly show that the matching of energy levels between the redox energy of the target gas and the conduction band of the materials plays an important role in selectively detecting the target gas in photoactive gas sensors; therefore, we propose a rational design rule to enhance the selectivity for various target gases. •Porosity-controlled SnO2 and SnO2@TiO2 heterostructures were fabricated by combining gas-flow thermal evaporation and ALD.•The photoactive gas-sensing properties of SnO2 and SnO2@TiO2 heterostructures was responsible for selective CO and HCHO gas.•The introduction of the TiO2 layer led to selective detection of HCHO as matching redox energy of target gas.•The gas-sensing characteristics were investigated by a modulation of charge transport and active materials to target gas.
ISSN:0925-4005
1873-3077
DOI:10.1016/j.snb.2022.131486