Scanning tunneling microscopy identification of atomic-scale intermixing on Si(100) at submonolayer Ge coverages

The positions of Ge atoms intermixed in the Si(100) surface at very low con centration are identified using empty-state imaging in scanning tunneling m icroscopy. A measurable degree of place exchange occurs at temperatures as low as 330 K. Contrary to earlier conclusions, good differentiation between Si atoms and Ge atoms can be achieved by proper imaging conditions.