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ACS Appl Mater Interfaces

Title:		Al(2)O(3)/ZnO Heterostructure-Based Sensors for Volatile Organic Compounds in Safety Applications
Author(s):		Lupan O; Santos-Carballal D; Magariu N; Mishra AK; Ababii N; Kruger H; Wolff N; Vahl A; Bodduluri MT; Kohlmann N; Kienle L; Adelung R; de Leeuw NH; Hansen S;
Address:		"Department of Materials Science, Chair for Functional Nanomaterials, Faculty of Engineering, Christian-Albrechts Universitat zu Kiel, Kiel, Kaiserstrasse 2, D-24143 Kiel, Germany. Center for Nanotechnology and Nanosensors, Department of Microelectronics and Biomedical Engineering, Faculty of Computers, Informatics and Microelectronics, Technical University of Moldova, 168 Stefan cel Mare str., MD-2004 Chisinau, Republic of Moldova. Department of Physics, University of Central Florida, Orlando, Florida 32816-2385, United States. School of Chemistry, University of Leeds, Leeds LS2 9JT, United Kingdom. Department of Physics, School of Engineering, University of Petroleum and Energy Studies (UPES), Energy Acres Building, Bidholi, Dehradun 248007, Uttrakhand, India. Department of Materials Science, Chair for Synthesis and Real Structure, Faculty of Engineering, Christian-Albrechts Universitat zu Kiel, Kiel, Kaiserstrasse 2, D-24143 Kiel, Germany. Department of Materials Science, Chair for Multicomponent Materials, Faculty of Engineering, Christian-Albrechts Universitat zu Kiel, Kiel, Kaiserstrasse 2, D-24143 Kiel, Germany. Fraunhofer Institute for Silicon Technology (ISIT), Itzehoe, Fraunhoferstrasse 1, Itzehoe D-25524, Germany. Department of Earth Sciences, Utrecht University, Princetonlaan 8a, 3584 CB Utrecht, The Netherlands"
Journal Title:		ACS Appl Mater Interfaces
Year:		2022
Volume:		20220615
Issue:		25
Page Number:		29331 - 29344
DOI:		10.1021/acsami.2c03704
ISSN/ISBN:		1944-8252 (Electronic) 1944-8244 (Linking)
Abstract:		"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 Al(2)O(3)/ZnO heterolayer-based sensors. We have also developed an approach to tune the sensor selectivity by changing the thickness of the exposed amorphous Al(2)O(3) layer from 5 to 18 nm. Columnar ZnO films are prepared by a chemical solution method, where the exposed surface is decorated with an Al(2)O(3) nanolayer via thermal atomic layer deposition at 75 degrees C. We have investigated the structure and morphology as well as the vibrational, chemical, electronic, and sensor properties of the Al(2)O(3)/ZnO heterostructures. Transmission electron microscopy (TEM) studies show that the upper layers consist of amorphous Al(2)O(3) films. The heterostructures showed selectivity to 2-propanol vapors only within the range of 12-15 nm thicknesses of Al(2)O(3), with the highest response value of approximately 2000% reported for a thickness of 15 nm at the optimal working temperature of 350 degrees C. Density functional theory (DFT) calculations of the Al(2)O(3)/ZnO(1010) interface and its interaction with 2-propanol (2-C(3)H(7)OH), n-butanol (n-C(4)H(9)OH), ethanol (C(2)H(5)OH), acetone (CH(3)COCH(3)), hydrogen (H(2)), and ammonia (NH(3)) show that the molecular affinity for the Al(2)O(3)/ZnO(1010) interface decreases from 2-propanol (2-C(3)H(7)OH) approximately n-butanol (n-C(4)H(9)OH) > ethanol (C(2)H(5)OH) > acetone (CH(3)COCH(3)) > hydrogen (H(2)), 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"
Keywords:		Al2O3 Dft VOCs ZnO gas response gas sensors heterojunctions semiconducting metal oxides;
Notes:		"PubMed-not-MEDLINELupan, Oleg Santos-Carballal, David Magariu, Nicolae Mishra, Abhishek Kumar Ababii, Nicolai Kruger, Helge Wolff, Niklas Vahl, Alexander Bodduluri, Mani Teja Kohlmann, Niklas Kienle, Lorenz Adelung, Rainer de Leeuw, Nora H Hansen, Sandra eng 2022/06/16 ACS Appl Mater Interfaces. 2022 Jun 29; 14(25):29331-29344. doi: 10.1021/acsami.2c03704. Epub 2022 Jun 15"