Deposition Rate Effect of Alq3 Thin Film Growth: A Kinetic Monte Carlo Study

Abstract

This paper is the winner of the Young Scientist Award at the Asian Chemical Congress in Kuala Lumpur, 2007. Applying the Kinetic Monte Carlo (KMC) technique, we successfully investigated the effect of deposition rate on the growth pattern of an Alq3 thin film. In good agreement with experimental results, our simulation results indicate that there exists a transition growth in terms of the deposition rate that corresponds to the transition between the island growth and random deposition growth. In the regions of island growth (where the deposition rate is lower than 1.1 Å s–1) and random deposition growth (where the deposition rate is higher than 3 Å s–1), the surface morphology is not suitable for luminant devices because of a high roughness, a larger inner vacancy ratio at higher deposition rate, and low homogeneity at lower deposition rate conditions. Within the transition growth region (deposition rate is between 1.1 and 3.0 Å s–1), the homogeneity of the film surface improves as the deposition rate increases. Not only does the pattern of the island structures become blurred, but the inner vacancy ratio and surface roughness also remain low as the deposition rate increases. From our results, there may exist a deposition rate to optimize the Alq3 film with a suitable surface morphology for luminant devices.