Onset of Interstitial Diffusion Determined by Scanning Tunneling Microscopy

A new method using variable temperature scanning tunneling microscopy (STM) to determine the onset temperature of the diffusion of self-interstitial atoms is presented. The interstitials are produced by a low fluence of Ne⁺ (4.5 keV) bombardment of Pt(111) at 20 K. At 22 K, the interstitials become mobile and migrate to the surface where they pop out and can be detected as new adatoms by STM. The time dependence of the appearance of the interstitials at the surface is measured for two temperatures, allowing estimation of the diffusion parameters.