Sensitive material of tungsten trioxide (WO₃) due to its high sensitivity, short response and recovery time, easy to be measured and controlled, low cost and other advantages for NO_x, NH₃ and other gases, is considered to be one of the most application prospective and promising gas-sensitive materials. However, a pure tungsten trioxide gas sensor has the shortcoming of high operating temperatures (About 250°C), thus to increase the complexity and instability of integration and miniaturization of the sensing system, thereby to reduce WO₃ gas sensor operating temperature has become a research focus.

 

Under such a circumstance, the porous silicon has attracted the researchers’ attention, the loose porous structure of a large surface area which formed by corrosion. The porous silicon has high chemical activity and to be a new promising room temperature sensitive material which has the property of ammonia-sensitive. However, it has shortcomings of lower sensitivity and slower response speed, longer recovery time than other sensitive materials. Thus, there is a study pointed out that a porous silicon substrate of WO₃ nano-thin film gas sensor, which combines the advantages of porous silicon and WO₃, has the properties of low temperature ( Room temperature) and high sensitivity.

 

The preparation steps of porous silicon substrate WO₃ nano-film gas sensor are as follows:

1. Prepare porous silicon substrate on the surface of sided polished ρ+ monocrystalline silicon by using double cell electrochemical etching method;

2. Place the porous silicon substrate in a vacuum chamber of ultrahigh vacuum magnetron sputtering equipment, and sputtered by target of pure metal tungsten to prepare porous silicon substrate WO₃ nano-thin film;

3. The prepared porous silicon substrate WO₃ nano-thin film is carried out an annealing treatment in a high temperature furnace of 400~600 ℃;

4. Then goes on the electrode coating to generate porous silicon substrate WO₃ nano-thin film gas sensor.