Effect of the Porous Silicon Layer Structure on Gas Adsorption

The paper deals with the study of the effect of the morphology and structure of crystallites of p-Si layer on the adsorption of gas sensors. The porous layer was obtained by electrochemical anodization at anodizing current from10 to 60 mA and anodizing time from 5 to 30 min. The sensors were created as p-Si structures: PdAu-Si:GeAuNiAu by electron-beam evaporation. The porous layer surface was studied with optical microscopy, and the crystallite structure was examined with FTIR technique. It has been discovered that the anodization modes have a direct effect on the deformation vibrations of the SiHx group in wavenumbers from 700 to 950 cm – 1. At the boundaries of the crystallites, compressing stresses arise causing a decrease in Si–O–Si bond in wavenumbers from 1060 to 1160 cm – 1. It has been demonstrated the increasing effect of SiHn stretching bonds and SiOxHy complexes (absorption peaks at 2116 cm – 1 and 2340 cm – 1 respectively). The variation of anodizing time has a stronger effect on the structure of the porous layer than the variation of anodizing current. The adsorption sensitivity of the porous layer has been determined by the relative change in conductivity. The data obtained make it possible to conclude that the anodization mode affects the adsorption of gas sensors. This conclusion correlates with the data obtained with FTIR method in crystallites structure.