Monte Carlo simulation of the subsurface growth mode during pulsed laser deposition

The pulsed laser deposition (PLD) growth of aluminum (Al) metal in the presence of noble background gases is studied using a Monte Carlo model constructed on the basis of srim 2010 calculations. It is shown that Al ions are deposited with a high kinetic energy of about 100 eV. These high kinetic incident energies lead to the implantation of ions into the existing film and resputtering from its surface. The consequent film growth is in the subsurface or subplantation growth mode, in which the material does not grow on top of the already deposited film. It is proved that by considering the role of resputtering, which is neglected in other theoretical models of PLD, experimentally observed deviations from the stoichiometric growth of multicomponent materials and dips in thickness profiles of elemental materials at the film center can be explained. The calculated implantation depths are also consistent with the reported measured ones. Taking into account the role of sputtering yield in calculating the deposition rate of the material, and evaluating the mean number of produced vacancies inside the growing film, two different approaches are proposed for the optimal growth of materials in PLD. To obtain high quality thin films, one should use a noble gas that ensures higher mass ratios (the ratio of the ablated ion to the gas atomic masses) at higher pressures; however, to achieve the highest growth speeds, higher mass ratios at lower pressures are recommended.