Surface Thermomigration of Eutectic Droplets and Molecular Clusters

Article presents overview of publications that form two new directions in the development of the thermomigration method as applied to micro- and nanotechnology. A common characteristic of these areas is the mass transfer of matter on atomically clean surfaces under the influence of temperature gradients. However, there is a significant difference both in the type of objects under consideration and in the mechanisms of the processes. In one case, the movement of eutectic droplets on the surface of semiconductor crystals is studied. The obtained results are generally consistent with the principles of the diffusion model of thermomigration. A distinctive feature of the process is that the recrystallized trace is represented by semiconductor nanowires. The possibility of precisely controlling the trajectory of the droplets using an electron beam, which creates a local temperature gradient, is demonstrated. This enables the practical application of these processes in the submicron size range. The second area of the research is the thermomigration of molecular clusters on the surface of nanomaterials. Graphene sheets and carbon nanotubes are considered as such materials. Because the clusters binding to the surface of these materials is extremely weak, they move freely under the applied temperature gradient, leaving no traces. Clusters migrate in the direction opposite to the temperature gradient vector, that is, toward the cooler region. It has been established that the primary driving force of this process is bending waves generated in nanomaterials. These waves propagate in the direction of the heat flow and propel the clusters, transferring some of their momentum of force to them. Examples of functional nanodevices created using this ballistic thermomigration mechanism are discussed.