Modeling evaporation, ion-beam assist, and magnetron sputtering of thin metal films over realistic time scales

A long-time-scale dynamics technique has been used to model the evaporation, ion-beam assist, and magnetron sputtering of thin metal films over realistic time scales. Two fcc metals have been investigated: silver and aluminum. We illustrate how the technique can be used to model growth of these films over experimental time scales, while investigating individual growth mechanisms and surface diffusion events. Long-time dynamics is achieved through an on-the-fly kinetic Monte Carlo method, which determines diffusion pathways and barriers, in parallel, with no prior knowledge of the involved transitions. It was found that Ag has the ability to grow smooth surfaces, using several mechanisms including multiple-atom concerted motion, exchange mechanisms, and damage and repair systems. Ag {111} and {100} grew dense, complete, and crystalline film when sputtering was simulated, whereas evaporation produced incomplete layers. The inclusion of Ar in the ion-beam-assisted evaporation of Ag {111} aided growth by transferring more energy to the surface atoms allowing increased diffusion. Al {111}, however, shows slightly different patterns; growth via evaporation and magnetron sputtering shows only slight differences and the inclusion of the ion-beam assist actually damages the film beyond repair, producing subsurface Ar clusters where Al atoms were displaced creating voids throughout the film. Al {100}, similar to Ag {100}, grows denser and more complete film when grown via sputtering rather than evaporation. Results show that the energy of the deposition method used plays a vital role in the resulting thin film and substrate quality.