Influence of surface smoothing on normal grain growth in Al films deposited from ionized vapor

Abstract

Unusually large normal grain growth rates and grain sizes were observed in Al films that were deposited from partially ionized vapor. The average grain size-to-thickness ratio ∼(8–25)h, where h is the film thickness, substantially exceeds those that were reported earlier for thin films and theoretically established limits. The materials thin film microstructure and surface morphology is being changed by ion bombardment during deposition. The roughness of the film surface dramatically increases along with initial growth of grain size up to an average value of 1.8 μm, however, the process abruptly turns to a reverse direction upon further grain growth under a self-ion bombardment beyond the average grain size of 3.5 μm. It is suggested the ion-enhanced smoothing of film surface and thermal grooves is responsible for large grain growth rate and unusually large grains.