Lupan Oleg, Santos-Carballal David, Magariu Nicolae, Mishra Abhishek Kumar, Ababii Nicolai, Krüger Helge, Wolff Niklas, Vahl Alexander, Bodduluri Mani Teja, Kohlmann Niklas, Kienle Lorenz, Adelung Rainer, de Leeuw Nora H, Hansen Sandra
Department of Materials Science, Chair for Functional Nanomaterials, Faculty of Engineering, Christian-Albrechts Universität 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.
ACS Appl Mater Interfaces. 2022 Jun 29;14(25):29331-29344. doi: 10.1021/acsami.2c03704. Epub 2022 Jun 15.
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 AlO/ZnO heterolayer-based sensors. We have also developed an approach to tune the sensor selectivity by changing the thickness of the exposed amorphous AlO layer from 5 to 18 nm. Columnar ZnO films are prepared by a chemical solution method, where the exposed surface is decorated with an AlO 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 AlO/ZnO heterostructures. Transmission electron microscopy (TEM) studies show that the upper layers consist of amorphous AlO films. The heterostructures showed selectivity to 2-propanol vapors only within the range of 12-15 nm thicknesses of AlO, 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 AlO/ZnO(1010) interface and its interaction with 2-propanol (2-CHOH), -butanol (-CHOH), ethanol (CHOH), acetone (CHCOCH), hydrogen (H), and ammonia (NH) show that the molecular affinity for the AlO/ZnO(1010) interface decreases from 2-propanol (2-CHOH) ≈ -butanol (-CHOH) > ethanol (CHOH) > acetone (CHCOCH) > hydrogen (H), 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.
在恶劣环境中监测挥发性有机化合物（VOCs），尤其是用于安全应用，是一个不断发展的领域，需要专门的传感器结构。在这项工作中，我们展示了基于柱状AlO/ZnO异质层的传感器对最常见VOCs的传感特性。我们还开发了一种方法，通过将暴露的非晶AlO层的厚度从5纳米改变到18纳米来调整传感器的选择性。柱状ZnO薄膜通过化学溶液法制备，其中暴露的表面在75°C下通过热原子层沉积用AlO纳米层进行修饰。我们研究了AlO/ZnO异质结构的结构、形态以及振动、化学、电子和传感器特性。透射电子显微镜（TEM）研究表明，上层由非晶AlO薄膜组成。异质结构仅在AlO厚度为12 - 15纳米的范围内对2 - 丙醇蒸汽表现出选择性，在350°C的最佳工作温度下，对于15纳米的厚度，报告的最高响应值约为2000%。AlO/ZnO(1010)界面及其与2 - 丙醇（2 - CHOH）、 - 丁醇（ - CHOH）、乙醇（CHOH）、丙酮（CHCOCH）、氢气（H）和氨气（NH）相互作用的密度泛函理论（DFT）计算表明，对AlO/ZnO(1010)界面的分子亲和力从2 - 丙醇（2 - CHOH）≈ - 丁醇（ - CHOH）>乙醇（CHOH）>丙酮（CHCOCH）>氢气（H）递减，这与我们对VOCs的气体响应实验一致。表面与吸附物之间的电荷转移以及相互作用原子的局部态密度，支持了计算出的分子偏好强度。我们的发现对于2 - 丙醇传感器的开发以及我们对异质结和顶部纳米层厚度对气体响应的影响的理解非常重要，迄今为止，这些在文献中尚未报道。
