Pulsed laser deposition of Pt on Pt(111) : nucleation and growth

Abstract

Pulsed Laser Deposition (PLD) is a method for growing thin films in which a high-power laser is used to vaporize the deposition material.<br />In contrast to conventional thermal evaporation, PLD is characterized by very energetic impinging particles (ions, 50 -- 350 eV) and nearly instantaneous deposition. To elucidate these effects, we have started by depositing a very low Pt dose at a temperature of about 50 K, at which the adatoms are immobile. The adatom densities were analyzed using low-temperature scanning tunneling microscopy (STM). For high ion energies we observed more adatoms than deposited. This can be explained by "failed sputtering", i.e. atoms displaced out of the surface, but with insufficient energy for escape into vacuum. We have also studied deposition of higher doses at temperatures from 120 to 310 K. For low ion energies, where "failed sputtering" does not occur, the island densities can be explained by the mean--field nucleation theory adapted for the high instantaneous deposition rate. At higher ion energies, "failed sputtering" leads to a significant increase of the island densities.<br />