Scanning tunnelling microscopic images of the (110) surface revealed the apparent presence of surface interstitial Sb atoms, when the sample bias voltage was small and negative. These surface interstitials disappeared at other bias voltages. The appearance of these so-called ethereal interstitials was explained in terms of below-surface second-layer Sb atoms. They appeared to lie above the surface due to the re-hybridized nature of the surface Sb wave-functions near to the top of the valence band.

Y.Liang, M.H.Tsai, W.E.Packard, J.D.Dow, H.A.Blackstead: Solid State Communications, 1993, 86[1], 33-7