Determination of the thermomigration force on adatoms
In cell phones and other devices, a large temperature difference across a microcircuit can cause atoms to migrate, eventually resulting in faulty electrical connections. This so-called thermomigration has now been tracked at the nanoscale. To quantify the resulting atomic fluxes induced by the thermal gradient we have used in operando low energy electron microscopy on a silicon surface under a thermal gradient of 10^4 K/m. The thermomigration is measured on metastable Si(111)-1×1 advacancy islands. The islands move in the direction of the thermal gradient at 0.26±0.06 nm/s. This reveals that the adatoms move towards the cold region and the effective force exerted on Si adatoms is 1.4±0.4 x10^-8 eV/nm. We quantify the heat of transport of Si adatoms Q*= 1.2±0.4 eV and show that it corresponds to the combined effects of adatom creation at step edges and adatom diffusion on atomically flat terraces. This article is published in Physical Review Letters
Phys. Rev. Lett. 131, 116202 – Published 15 September 2023