Initial Oxidation Process of Anodized Porous Silicon with Hydrogen Atoms Chemisorbed on the Inner Surface

Abstract

The initial stage of oxidation of anodized porous silicon (PS) at low temperature (\lesssim208°C) has been investigated using a conventional infrared (IR) spectroscopy technique. After the oxidation in air, four extra IR absorption peaks appeared in the Si-H stretching band (2000∼2300 cm^-1). The origins of these peaks have been assigned as excitations of Si-H oscillators for various SiH _n (n=1∼3) bonded by oxygen atom(s). The progress of the oxidation without breaking Si-H bonds was linearly dependent on the square root of the oxidation time, indicating a diffusion-limited process even for the initial stage. The activation energy of this process was 0.60 eV. The role of chemisorbed hydrogen atoms in the oxidation process is discussed.