Structural Change of Crystalline Porous Silicon with Chemisorption

Abstract

Anodized porous silicon (PS) has been investigated in relation to its structural change at elevated temperatures of ≦1100°C in a vacuum by means of infrared spectroscopy, scanning electron microscopy, X-ray diffraction and gas adsorption techniques. The structural change observed is strongly dependent on foreign atoms chemisorbed or bonded to Si atoms on the pores in PS; in the case of chemisorption of H atoms, a significant change in the pore structure is induced, while in the case of O, the formation of thin oxide walls (1–2 nm) prevents Si atoms from moving about. These results are compared with molecular orbital calculations (AM1 method) for Si₁₄H₂₀ and its related clusters. The importance of the surface energy is consistently indicated for the structural change observed.