Gold-catalysed porous silicon for NO x sensing

Abstract

Porous silicon (PS), obtained by electrochemical anodization of an n-type silicon wafer, was catalysed by sputtering gold onto the surface (4, 8, 15 and 40-nm nominal thickness). Investigation by Rutherford backscattering spectroscopy (RBS) and by electron microscopy showed that gold did not form a continuous layer, but rather formed clusters penetrating into the pores of PS by about 1 μm. A variation of the sample conductivity in the presence of a few parts per million of NO 2 and NO was recorded at room temperature. We demonstrated that, as a result of Au catalysation, PS is suitable for sensing nitrogen oxides with negligible influence by interfering gases such as CO, CH 4 or methanol. Indeed, we found that humidity appreciably affected the response.