Hydrogen Sensor Based on Electroless Plating of Palladium on the Porous Silicon

Pd thin film has drawn renewed interest in recent years due to its importance in catalytic coating applications and sensors for gases such as hydrogen. Hydrogen has received considerable attention due to its application as a clear, abundant and inexpensive fuel. Because H2 has high solubility and diffusivity in Pd (up to 900 times of Pd volume), it changes electrical properties of Pd base devices [1]. Thin film of Pd has been prepared by different deposition techniques like physical and chemical methods. For rough and porous surface that provide larger gas surface interaction, chemical methods have been developed to deposit on porous substrates [2]. Although electroless is a simple and inexpensive chemical method but it is complex due to existence of many effective factors [3]. So, optimization of them is very important. In this work we used electrochemical technique to produce macroporous Si (PS) substrates because of its large specific surface area, chemical activity and its compatibility to electronic systems. Then, PS samples were immersed in solution of PdCl2 for various length of time. To measure the sensitivity, the variation of the electrical current in 1V bias voltage was carried out.