CHARACTERIZATION OF HF-TREATED SI(111) SURFACES

The properties of Si(111) surfaces treated in various HF solutions are characterized by photoluminescence (PL), scanning tunneling microscopy (STM) and Fourier-transform infrared spectroscopy (FTIR). STM images show that the surfaces dipped in normal HF solution are terminated by Si-H, Si-H-2 and Si-H-3 bonds with high step density, while those treated by pH-modified buffered HF are atomically flat with wide terraces terminated mostly by Si-H bonds. Multistage oxidation processes via surface defects, atomic steps, kinks or terraces are suggested by a change in the PL intensity of HF-treated Si surfaces with exposure to oxygen. The PL measurement also shows that the surface treated with pH-modified buffered HF or boiled deionized water shows much better stability against oxidation than conventional HF-treated Si surfaces, which is consistent with the surface structure observed by means of STM.