Chemical passivity of III-VI bilayer terminated Si(111)

The chemical stability of Si(111), terminated with bilayer AlSe and GaSe, upon exposure to atmosphere, $N2$ and $O2$⁠, was investigated with core-level and valence band photoelectron spectroscopy. Si(111):GaSe and Si(111):AlSe both form stable, unreconstructed surfaces with no states in the silicon energy gap; their atomic structures are nearly identical. However, similarities in surface electronic and atomic structure do not imply similar chemical passivity. While Si(111):GaSe is largely unaffected by the exposures, Si(111):AlSe reacts irreversibly with both pure $O2$ and atmosphere, removing over $13$ of the Se and permanently destroying long-range order.