Highly C-axis oriented LiNbO3 thin film on amorphous SiO2 buffer layer and its growth mechanism

Abstract

LiNbO3 waveguiding films with highly C-axis orientation and superior crystallographic quality have been deposited on the amorphous SiO2 buffer layer of Si wafer by pulsed laser deposition (PLD) technique. X-ray diffraction, high-resolution electron transmission microscopy and atomic force microscopy were applied to characterizing the quality and orientation of LiNbO3 thin film, and the optimized deposition conditions have been determined for C-axis oriented growth. LiNbO3 thin films on amorphous SiO2 buffer layer were composed of intimate arrangements of quadrangular single crystal domain (150 nm × 150 nm) with C-axis orientation, and displayed sharp interface structures. The measurements of prism coupling technique indicate that the laser can be coupled into the LiNbO3 film and TE and TM waveguiding modes were detected. In addition, the possible mechanism of oriented growth on amorphous buffer layer and “film-substrate effects” were discussed briefly, which suggests that its growth mechanism is likely analogous to the Volmer model with characteristics of three-dimensional islands nucleation on the smooth crystal surface.