Synthesis of W-doped Cr2O3 thin films and their application in isobutylene sensing
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摘要:
挥发性有机污染物(VOCs)气体广泛存在于生产生活中，异丁烯是一种常见的VOCs气体，其危害是容易让人窒息，且其与空气混合能形成爆炸性混合物，遇热源和明火有燃烧爆炸的危险，工业生产中亟需一种性能优良的气体传感器来对其进行快速检测，但市场上专门用于检测异丁烯的气体传感器还鲜有报道。本文采用气溶胶辅助化学气相沉积(AACVD)技术在氧化铝基底上分别沉积得到纯氧化铬(Cr2O3)薄膜及W掺杂Cr2O3(W/Cr2O3)的薄膜材料，并将其制备成气体传感器，对比研究了两种气体传感器对异丁烯的气敏性能，气敏测试结果表明，基于W/Cr2O3薄膜所制备的气体传感器相较于单一的Cr2O3气体传感器对异丁烯气体表现出较高的灵敏度，并展现出良好的稳定性、抗湿性和气体选择性，其性能优良，制备成本较低，有望实现商业化应用。 气体传感器示意图 (a), Cr2O3薄膜的SEM照片 (b), Cr2O3气体传感器对异丁烯气体的灵敏度变化曲线 (c), W/Cr2O3薄膜的SEM照片 (d), W/Cr2O3气体传感器对异丁烯气体的灵敏度变化曲线 (e). Abstract: In order to effectively monitor isobutylene gas, Cr2O3 and W-doped Cr2O3 (W/Cr2O3) films were successfully synthesized via aerosol-assisted chemical vapor deposition (AACVD) technique on the surface of alumina substrate. The microstructure, crystal structure, and elemental binding valence of Cr2O3 and W/Cr2O3 films were analyzed by SEM, TEM, XRD, and XPS. The results show that Cr2O3 film is composed of nanoparticles with the particle size of about 50 nm, a thickness of about 20 μm, and its structure is relatively loose. However, the thin film obtained by W doping Cr2O3 has a compact structure, and the size of nanoparticles is about 15 nm, which is remarkably reduced due to the introduction of W into the Cr2O3 crystal lattice. Both Cr2O3 and W/Cr2O3 films have a single hexagonal crystalline structure. The gas sensitivity test results show that the sensitivity of the gas sensor based on W/Cr2O3 film towards 2×10-5 isobutene increases from 1.11 to 3.55 compared with the Cr2O3 gas sensor at 400°C, and W/Cr2O3 gas sensor exhibits good stability, moisture resistance and gas selectivity.-
Key words:
- W doping /
- Cr2O3 thin films /
- gas sensor /
- isobutylene /
- gas sensing mechanism
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图 1 气溶胶辅助化学气相沉积的反应原理图
Figure 1. Reaction schematic diagram of an aerosol-assisted chemical vapor deposition
图 3 Cr2O3薄膜的SEM表面图 (a) 和截面图 (b)；W/Cr2O3薄膜的SEM照片 (c) 和TEM照片 (d)
Figure 3. SEM surface image (a) and cross section image (b) of Cr2O3 thin film; SEM image (c) and TEM image (d) of W/Cr2O3 thin film
图 4 Cr2O3和W/Cr2O3薄膜在衍射角为 (a) 21–66°和 (b) 30–40°范围内的XRD图谱
Figure 4. XRD patterns of Cr2O3 and W/Cr2O3 thin films in the diffraction angles of (a) 21–66° and (b) 30–40°
图 5 Cr2O3和W/Cr2O3薄膜的XPS能谱：(a) Cr 2 p;(b) O 1 s; (c) W 4 f
Figure 5. XPS spectra of Cr2O3 and W/Cr2O3 thin films: (a) Cr 2 p; (b) O 1 s; (c) W 4 f
图 6 Cr2O3和W/Cr2O3气体传感器在不同工作温度条件下对2×10−5 C4H8气体的灵敏度
Figure 6. Sensitivity of Cr2O3 and W/Cr2O3 gas sensors towards 2×10−5 C4H8 at different operating temperatures
图 7 (a) Cr2O3和W/Cr2O3气体传感器在最佳工作温度条件下对不同浓度C4H8气体的灵敏度变化曲线; (b) C4H8气体浓度与灵敏度之间的拟合线
Figure 7. (a) Sensitivity curve of Cr2O3 and W/Cr2O3 gas sensors towards different concentrations of C4H8 gas at the optimal working temperature; (b) Fitting lines between C4H8 gas concentration and sensitivity
图 8 不同工作温度及不同C4H8浓度条件下
(a) Cr2O3气体传感器和 (b) W/Cr2O3气体传感器对C4H8气体的灵敏度变化曲线
Figure 8. Sensitivity curves of Cr2O3 gas sensors (a) and W/Cr2O3 gas sensors (b) towards C4H8 gas at different working temperatures and different concentrations
图 9 (a) Cr2O3和 (b) W/Cr2O3气体传感器在不同相对湿度条件下对8×10−5 C4H8气体的灵敏度
Figure 9. Sensitivity of (a) Cr2O3 and (b) W/Cr2O3 gas sensors to 8×10−5 C4H8 gas at different relative humidity
Figure 10. Selectivity of Cr2O3 and W/Cr2O3 gas sensors towards different detected gases at 400°C
图 11 气敏反应机制图: (a) Cr2O3薄膜；(b) W/Cr2O3薄膜
Figure 11. Schematic illustration of gas sensing mechanism: (a) Cr2O3 thin film; (b) W/Cr2O3 thin film
表 1 传感器的重复性和一致性
Table 1. Repeatability and consistency of gas sensors
Sensors Repeatability RSD% Average response Consistency RSD% Cr2O3-1 0.72 1.04 3.42 Cr2O3-2 1.27 1.11 Cr2O3-3 0.49 1.05 W/Cr2O3-1 3.51 3.67 3.56 W/Cr2O3-2 4.94 3.49 
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