Vibrational properties of arsenic on Si(111)

Abstract Clean silicon substrates. Si(111), were arsenic capped in a molecular beam of As 4 molecules. These samples were investigated by Raman scattering after transferring them through air into another UHV chamber for analysis. The thick as deposited As layers are identified as being amorphous. With increasing exposure time to air they become partly oxidized. Heating of these layers was then performed in steps from room temperature up to 550°C. As revealed by Raman scattering the amorphous arsenic is removed at first. Around 350–400°C two peaks appear in the Raman spectra at 235 and 356 cm −1 . Since at this temperature range all but one monolayer of ordered (1 × 1) As has been desorbed, these peaks are interpreted as a doubly degenerated stretching and a bending vibrational mode of the first monolayer of As on Si(111). The peaks disappear above 550°C. the temperature where the arsenic monolayer desorbs. Air exposure also causes the peaks to vanish.