Gold-catalysed porous silicon for NOx sensing

Porous silicon (PS), obtained by electrochemical anodization of an n-type s ilicon wafer, was catalysed by sputtering gold onto the surface (4, 8, 15 a nd 40-nm nominal thickness). Investigation by Rutherford backscattering spe ctroscopy (RBS) and by electron microscopy showed that gold did not form a continuous layer, but rather formed clusters penetrating into the ports of PS by about 1 mu m. A variation of the sample conductivity in the presence of a few parts per million of NO, and NO was recorded at room temperature. We demonstrated that, as a result of Au catalysation, PS is suitable for se nsing nitrogen oxides with negligible influence by interfering gases such a s CO, CH, or methanol. Indeed, we found that humidity appreciably affected the response. (C) 2000 Elsevier Science S.A. All rights reserved.