Role of substrate step bunches on the growth behavior of LiNbO 3 thin film on α-Al 2O 3 substrate

Abstract

In order to investigate the influence of step height of substrate on the morphology of thin film, the substrates with mono and bunched steps structures were employed. (0 0 0 1) α-Al 2O 3 was used as substrate, on which LiNbO 3 thin films were grown by pulsed laser deposition. Prior to the deposition, nominally flat substrate with a miscut of less than ±0.5° and vicinal substrate with a miscut angle of 2° were annealed at 1000 and 1400 °C in air for 2 h, respectively. After the annealing, the steps with heights of 0.2 and 10 nm were formed on their surface. The surface roughness of the film grown on the substrate with a step height of 10 nm was improved over 2.5 times than that of the film on the substrate with 0.2 nm step height. This can be explained by understanding that raising the step height enhances the step–adatom attractive energy in the vicinity of steps so that the incorporation of adatoms at steps can take place more readily, which leads to quasi step-flow growth mode.