Effect of deposition rate on morphology evolution of metal-on-insulator films grown by pulsed laser deposition

Abstract

Ag films were grown by pulsed laser deposition on insulating SiO2 and mica substrates and exhibited a morphological progression beginning with nucleation of three-dimensional islands and culminating in a continuous, electrically conducting film. The rate of advancement through this progression with increasing pulse frequency was studied with experiments and with kinetic Monte Carlo (KMC) simulations. Experiments at 93 and 135 °C give exponents of −0.34 and −0.31, respectively, for the scaling of the electrical percolation thickness with pulse frequency. Simulations predicted an exponent of −0.34, in excellent agreement with the experiments. Both of these values agree well with the previously reported analytic value of −0.33 for the scaling of the morphology transition thickness with average flux in continuous deposition. Simulations also predicted that data collapse for island density vs amount deposited would be observed for experiments run at the same value of the parameter B/f at constant amount deposited per pulse, where B is the kinetic rate constant for coalescence and f is the pulse frequency. Measurements of the percolation transition were consistent with this prediction. These findings indicate that the elementary processes included in the KMC simulation—substrate terrace diffusion, irreversible aggregation of hemispherical islands, and two-island coalescence, but neglecting the effects of kinetic energy—are sufficient to explain the behavior observed when the pulse rate is varied at constant kinetic energy.