WO₃ thin film gas sensor is using the gas sensitive semiconductor property of tungsten trioxide (WO₃), a potential sensitive material which has sensitivity to NOx, H₂S, CO, NH₃, C₂H₅OH and other gases; when it is exposed to the specific gas, oxygen is adsorbed from the air as an electron acceptor states in the band gap material of tungsten trioxide, surface reaction leading to the acceptor states in the portion of the surface coverage changes, causing the change of Electrical conductivity, thus to realize detecting specific gas concentration.

 

Preparation of WO₃ thin film gas sensor is generally sol-gel process: First prepare solution or a homogeneous sol with tungsten atom highly dispersed, and then goes on the post-chemical and physical treatment to form a homogeneously dispersed solid film on the substrate’s surface. A new production method for preparing WO₃ thin film gas sensor is through facing targets magnetron sputtering method, which the steps are showed following:

1. Wash the p-type monocrystalline silicon chip in concentrated sulfuric acid, deionized water, acetone and ethanol in turn;

2. Place the cleaned monocrystalline silicon chip in the ultra-high vacuum magnetron sputtering equipment with working gas of argon and the target of platinum to prepare interdigitated platinum electrode on the substrate’s surface by magnetron sputtering method; 

3. Use tungsten as a target, in ultra-high vacuum magnetron sputtering equipment with working gases of argon and oxygen, to form tungsten trioxide thin film on the substrate’s surface with interdigitated platinum electrode by magnetron sputtering method;

4. Carry out a heat-treatment in the air to finally get WO₃ thin film gas sensor.

 

Advantages of the magnetron sputtering method is that the obtained uniform film, high purity, good adhesion to the substrate film, parameters easy to be controlled, and very sensitive to ammonia. However, this method requires higher in equipment and raw materials than traditional ways, and results in weaker advantages in cost, may be more suitable for laboratory preparation, but not suitable for industrial mass production.