Hydrogen terminated Si(100) surfaces studied by scanning tunneling microscopy, x-ray photon spectroscopy, and Auger electron spectroscopy

Si (100) surfaces were terminated by hydrogen atoms by means of several chemical methods: (1) Conventional dipping into hydrofluoric acid (HF) followed by immersion into several HF solutions of various concentrations diluted by ethanol (C₂H₅OH), and (2) hydrogenated porous silicon film anodically formed in an HF and C₂H₅OH solution. Quite clear STM images with atomic steps were obtained for HF-dipped surfaces during the first several hours in a dry N₂ambient. The observable time was longer for surfaces dipped into less dilute HF. Atomic steps could be observed on the anodically produced porous silicon surfaces even after ten days exposure to air. These phenomena were consistent with the initial oxidation behaviors of the surfaces studied by x-ray photon spectroscopy (XPS) and Auger electron spectroscopy (AES).