Heterojunctions, formed at the interface between two different materials, have attracted much attention as a gas-sensing material. In particular, Si/tungsten oxide (WO_X) heterojunctions are well known to be capable of gas detection at low temperature and to increase the sensitivity to and selectivity of NO₂. However, during the fabrication process of the Si/WO_X nanostructure-based sensor it is difficult to control the synthesis position of the nanostructures; hence, it is complicated or time consuming. In this work, semiconducting gas sensors based on n-type silicon/n-type suspended tungsten oxide nanowire (WO_X NW) heterojunctions were fabricated by stress-induced method for WO_X NW synthesis on Si MEMS structures. With this fabrication technique, the growth position of the WO_X NWs can be controlled by patterning of the WO_X seed film, and the NWs can be synthesized by simply heating the seed film for 20 min. In addition, all fabrication processes consist of batch-processes. Unlike conventional WO_X-based sensors, the resistance of this sensor is reduced in the presence of NO₂, an oxidizing gas, due to the band bending phenomenon of the Si/WO_X NW heterojunction. The fabricated sensor can detect 500 ppb of NO₂ and exhibits excellent selectivity to CO and toluene, which are exhaust gases, like NO₂. This selectivity will be particularly useful when using sensors to detect NO₂ in exhaust gases of automobiles or factories.

在两种不同材料之间的界面处形成的异质结作为一种气体传感材料引起了广泛的关注。特别地，众所周知，Si /氧化钨（WO _X）异质结能够在低温下进行气体检测，并且能够提高对NO ₂的灵敏度和选择性。然而，在基于Si / WO _X纳米结构的传感器的制造过程中，难以控制纳米结构的合成位置；因此，需要对纳米结构的合成进行控制。因此，这很复杂或很费时间。在这项工作中，通过应力诱导方法为WO _X制造了基于n型硅/ n型悬浮氧化钨纳米线（WO _X NW）异质结的半导体气体传感器。Si MEMS结构上的NW合成。利用这种制造技术，可以通过对WO _X种子膜进行图案化来控制WO _X NW的生长位置，并且可以通过简单地将种子膜加热20分钟来合成NW。此外，所有制造过程都包括批处理过程。与传统的基于WO _X的传感器不同，由于Si / WO _X NW异质结的能带弯曲现象，在存在氧化气体NO _2时，该传感器的电阻会降低。制成的传感器可以检测500 ppb的NO _2，并且对像NO ₂这样的废气CO和甲苯表现出出色的选择性。当使用传感器检测汽车或工厂废气中的NO ₂时，这种选择性将特别有用。