An FTIR study of porous silicon layers exposed to humid air with and without pyridine vapors at room temperature

Oxidation processes can strongly influence the properties of porous silicon (PS) material. In this paper, we present the results of FTIR studies for the oxidation process of PS exposed to humid air alone or together with saturated pyridine vapor at room temperature in the time range from 0.1 to 10,000 min. The oxidation has been followed by recording the time evolution of the IR absorption intensities of the main species involved in the process, namely: Si–Hx, OySi–Hx, Si–OH and Si–O–Si. We found that in the presence of pyridine the oxidation is much faster. We show that the asymptotic value of silicon oxide amount is the same in both cases (with or without pyridine) and is strictly related to the original content of SiH surface species present in the sample. The role of the pyridine in the oxidation process is discussed.