Manipulating surfaces by thermomigration: towards thermal tweezers – THERMOTWEEZ

Thermal gradients are known to affect atomic diffusion in bulk multicomponent materials, leading to thermomigration. A comprehensive study of thermomigration for surfaces is missing and we plan to address it within this project with the aim to use thermomigration to control surface morphologies. We propose a strategy in two parts: (i) We will study how thermomigration bias atomic diffusion by low-energy-electron-microscopy (LEEM) in-real-time observations of the motion and shape change of 2D clusters on Si and Ge surfaces. 2D domains and 3D droplets of Au on Si and Ge will also be investigated. A modified LEEM sample holder will be developed and a laser with appropriate optics will be implemented on the microscope. Kinetic Monte Carlo simulations will help the interpretation of the experiments. A continuum description for the motion of atomic steps and of 2D clusters under the Burton-Cabrera-Franck formalism will be developed. (ii) We will prove that thermomigration can be used to move and shape nanostructures to tailor material surfaces. We have the ambition to develop the “thermal tweezers”, an instrument theoretically predicted to be possible: Using a laser beam and special optics, we will move a nanostructure along a pre-identified trajectory and precisely position it on a surface.