Oxidation of Porous Silicon under Water Vapor Environment

The oxidation process of porous silicon in wet air at 323 K was investigated by infrared spectroscopy, particularly focusing on the behavior of the stretching vibrations of Si‐H. The fine structure of the absorption bands were clarified with help of vibrational analysis by ab initio molecular orbital calculations. Absorption bands at 2150–2300 cm −1 are assigned to the Si‐H vibrations due to , , and in order of increasing frequency, respectively. The presence of causes Si‐Si bond breaking with dissociative adsorption of , resulting in an increase in the amount of Si‐H species, which is readily oxidized. The bond breaking causes a prominent enhancement of in the oxidized states. This contrasts with the behavior of the oxidation in dry air where the introduction of oxygen keeps the amount of Si‐H species constant in the course of the oxidation and the growth of and in addition to .