ZnO基纳米材料的制备及其气敏器件的研究

THE PREPARATION OF ZnO-BASED NANOMATERIALS AND ITS GAS SENSING PROPERTIES

唐运湘

11649117

硕士

信息功能材料与器件

吴文政

2018-05-30

2018-07-05

哈尔滨工业大学

深圳

在最近几年中，半导体金属氧化物纳米材料凭借其物理化学稳定性好、成本低以及易合成等优点在半导体催化领域和有害有毒气体的检测中得到了广泛地运用。作为n 型半导体中最具代表性的物质，ZnO 气敏性能优秀，是重要的气敏材料。本论文以ZnO 作为主要研究对象，采用半导体复合技术对ZnO 基的纳米复合材料的气敏性能与其组成、结构关系进行深入研究。首先，由于一维纳米结构具有较高的比表面积，和较小的的尺寸，其在气敏领域具有出色的用前景，因此选择了一维的ZnO 纳米材料作为研究起点，在实验中利用水热法，成功制备出尺寸、高度可控的ZnO 纳米棒，然后我们在结构、形貌及材料组合方面开展了进一步探索，考虑利用材料复合技术进行复合材料的制备，本论文采用原子层沉积的方法对ZnO 进行TiO2 表面改性，并将ZnO 纳米棒和ZnO/TiO2 复合纳米结构分别制备成气敏器件，测试其对各种氧化和还原气体的气敏性能，气敏结果表明，ZnO 纳米棒和ZnO/TiO2 复合纳米结构制备而成两种气敏器件的最佳工作温度均为160 ℃左右，且均对NO2 有较好的选择性，其中对NO2，ZnO 纳米棒的响应为68，ZnO/TiO2 复合纳米结构的响应为130。此外相比于ZnO 纳米棒，ZnO/TiO2 复合纳米结构对乙醇、丙酮和氨水等气体都具有更好的灵敏度和更快的响应-恢复时间。然后，本论文利用表面改性的方法尝试制备基于ZnO 的高性能的CO2传感器，因为由于CO2 分子的物理和化学性质都非常稳定，CO2 分子是属于sp2 杂化的非极性分子，C、O 原子通过双键结合形成离域大π键，电子分布均匀且十分稳定，CO2 很难与其他物质发生电子之间的转移，而半导体式金属氧化物的传感器是利用气体分子在材料表面脱附、吸附的过程中，电子在材料表面发生转移从而产生电学信号，因此CO2 不容易通过简单的金属氧化物传感器进行探测。所以本文从ZnO 气敏传感材料入手，重点研究利用NO2 和胺基等方式进行表面改性来提高ZnO 对CO2 的气敏性能，制备出低成本、结构简单、高响应度的CO2 传感器。

In recent years, metal oxide nanomaterials have been widely used in the field of semiconductor catalysis and detection of harmful toxic gases due to their high chemical stability, low cost, and ease of synthesis. As one of the most representative material in n-type semiconductor, ZnO gas sensitivity is excellent, which is one of the most important gas sensitive materials in the future. The work will explore the relationship between the fabrication methods, the surface modificaiton, the material property and its gas sensing performance.One-dimensional nanostructures have broad application prospects in the field of gas sensing due to their high specific surface area and radial dimensions to Debye's length. Based on this, we selected ZnO nanomaterial for the study, and successfully prepared the ZnO nanorods by the hydrothermal method. Then we further explored the structure, morphology of composite material to enhance the gas sensitivity by preparing composite material. In this work, ZnO is modified with TiO2 ultrathin layer by atomic layer deposition method. Then ZnO nanorods and ZnO/TiO2 composite nanostructures are respectively prepared into gas sensors and tested for various oxidizing and reducing gas. The gas sensitivity results show that the best working temperature of the two gas sensors fabricated by ZnO nanorods and ZnO/TiO2 composite nanostructures is about 160 °C, and both of them have better selectivity for NO2, where the ZnO nanorods have a response of 68, and the ZnO/TiO2 composite nanostructures have a response of 130. In addition, compared to ZnO nanorods, ZnO/TiO2 composite nanostructures have better sensitivity and faster response-recovery time for gases such as ethanol, acetone, and ammonia. The reason for the enhanced gas sensitivity of ZnO/TiO2 composite nanostructures is possible due to the formation of a heterostructure between ZnO and TiO2, which significantly increases the sensitivity to oxidizing gases and has a better selectivity. The formation of heterojunction allows electrons to be transported to TiO2, which enhances the adsorption of oxidative gases. At the same time, the local heterojunction changes the contact barrier and makes it more sensitive to oxidizing gases, thereby increasing the selectivity of the material to oxidizing gases.Then,this work uses surface modification method to prepare a high-performance CO2 sensor based on ZnO. Because CO2 molecules are non-polar molecules belonging to sp2 hybrids, and O atoms combine to form large delocalized π bonds through double bonds, the electrons are uniformly distributed and stable. Electrons is difficult to transfer between CO2 and other substances. In the gas process of sensing, absorption and disabsorption of gas molecule would lead to the transfer of electrons between its gas molecule and material surface to generate a change of electrical signal. Therefore CO2 is not easily detected by a simple metal oxide sensor. This article starts with ZnO gas sensor materials and focus on the use of NO2 and -NH2 and other methods of surface modification to improve the gas sensitivity of ZnO to CO2.

ZnO 水热法 原子层沉积 TiO2 气体传感器 CO2

ZnO hydrothermal method ALD TiO2 gas sensor CO2

中文

联合培养

哈尔滨工业大学

唐运湘. ZnO基纳米材料的制备及其气敏器件的研究[D]. 深圳. 哈尔滨工业大学,2018.