Ballistic deposition model with surface diffusion for thin film growth on patterned substrates

Abstract

Ballistic deposition model is a simple computational model described the growth of thin film with void defect. To make it more realistic, a surface diffusion process is added into the model. In this work, different interpretations of this process result in two different models, a “conventional” model and a “realistic” model. To see the difference between these models, the film’s morphology, interface width and defect density are studied. Simulation results show that the films from both models have smoother surfaces with less void defect density when the substrate temperature is increased. However, high substrate temperature leads to oscillations of the interface width curve in the conventional model while the curve of the realistic model maintains a power law relation with growth time. When studying the growth on patterned substrates, the realistic model was used. Two types of substrate, a flat substrate and a periodic patterned substrate, were studied. Persistence probability is a quantity that provides information on how much the pattern of the substrate is kept after the growth process is complete. Here, we found that the persistence probabilities of the films grown on both substrates decrease with the growth time. If the time is fixed, the substrate temperature plays an important role in controlling the film’s pattern. We found that there is only a narrow window of temperature that the film can maintain its original pattern longest. Also, we found that if the flat part of the substrate is larger, the original pattern of the film can survive longer.