Functional Design of Semiconductor Gas Sensors for Development of Odor Sensors

本项目主要致力于半导体传感器的功能设计，开发能够检测三甲胺、二甲胺和氨等气味成分的传感器，具有高灵敏度和选择性。本文研究了内电极传感器的TMA气体灵敏度随厚度的变化规律。研究表明，优化设计传感器材料的厚度和TMA氧化催化活性对TMA气体传感器的发展至关重要。结果表明，负载3.0 wt% Pt的In_2O_3-MgO (5mol%) （3.0Pt/In_2O_3-MgO (5mol%)）是所有传感器中唯一对DMA的灵敏度高于TMA的。在3.0Pt/In_2O_3-MgO （5mol%）传感器表面涂覆TiO_2或0.5Pt/TiO_2层，进一步提高了DMA灵敏度。发现单层传感器的高DMA灵敏度是由于其产生亚胺的活性高，而产生NO_X的活性低。TMA氧化过程中产生的乙烯亚胺与传感器材料上化学吸附的氧反应更强，而NO_X是TMA氧化的产物，作为干扰气体。该双层传感器由In_2O_3-MgO （5mol%）传感层、In_2O_3-MgO （5mol%）传感层顶部的0.5Ir/TiO_2涂层和两层之间的电极组成，可以实现高的NH_3灵敏度。研究发现，选择NH_3氧化适中、不产生大量NO_X的传感器材料和NH_3将NO_X还原为N_2的活性较高的涂层是研制高灵敏度NH_3传感器的关键。

The present project was focused on functional design of semiconductorgas sensors for development of odor sensors capable of detecting of odor components, such as trimethylamine (TMA), dimethylamine (DMA) and ammonia, with high sensitivity and selectivity.Thickness dependence of TMA gas sensistvity of sensors equipped with interior electrodes have been investigated by employing semiconductor metal oxides loades with and without different amounts of noble metals. It has revealed that optimum design of both the thickness and the catalytic activity for TMA oxidation of sensor materials is of primary importance for the development of TMA gas sensors.It was found that In_2O_3-MgO (5mol%) loaded with 3.0 wt% Pt (3.0Pt/In_2O_3-MgO (5mol%)) was the only sensor which exhibited higher sensitivity to DMA than TMA at 300ﾟC,among the sensors tested. The DMA sensitivity was further enhanced by coating the surface of 3.0Pt/In_2O_3-MgO (5mol%) sensor with a TiO_2 or 0.5Pt/TiO_2 layr. The high DMA sensitivity of the single layr sensor was found to be attributed to its high activity for producing ethylenimine and less activity for producing NO_X. Ethylenimine produced during the oxidation of TMA is more reactive with chemisorbed oxygen on the sensor material, while NO_X are oxidation products of TMA and act as interference gases.High NH_3 sensitivity could be realized with the doible layr sensor consisting of an In_2O_3-MgO (5mol%) sensing layr, a 0.5Ir/TiO_2 coating layr atop the sensing layr and electrodes between these two layrs. It was found that selection of both the sensor materials having moderate NH_3 oxidation without producing large amounts of NO_X and the coating layr exhibiting high activity for reduction of NO_X into N_2 by NH_3 is of primary importance for developing an NH_3 sensor having high sensitivity.