Palladium Plating on Macroporous/Microporous Silicon: Application as a Hydrogen Sensor

Abstract

Porous silicon samples are obtained by electrochemical method on n‐type wafers in room light. Scanning electron microscopy showed that the porous structure consisted of macropores under a thin microporous layer. Placing the samples in Pd‐electroless solution causes the crakes inside the microporous layer and growth of the palladium particles in these crakes. However, removing the microporous layer by KOH solution with an ultrasonically assisted process makes the growth of rather uniform palladium particles on the surface in electroless plating. Variation of the electrical resistance in the presence of diluted hydrogen at room temperature revealed that the best samples have the ability to sense hydrogen at levels down to several hundreds of ppm. This value is far below the flammability limit of hydrogen gas.