Factors driving c-axis orientation and disorientation of LiNbO3 thin films deposited on TiN and indium tin oxide by electron cyclotron resonance plasma sputtering

We clarified critical factors affecting the crystallographic orientation of LiNbO3 (LN) thin films deposited by electron cyclotron resonance plasma sputtering on transparent conductive oxides, i.e., TiN and indium tin oxide (ITO). When LN films were crystallized during sputtering on amorphous TiN, insufficient crystallization (400 degrees C), a roughened TiN surface by crystallization (460 and 530 degrees C), and oxidization of TiN (600 degrees C) interfered with the production of c-axis oriented textured film. Solid-phase crystallization of amorphous LN film on amorphous TiN through rapid thermal annealing provided a solution to disorientation factors. Because of the low crystallization temperature of ITO, both crystallization during sputtering and solid-phase crystallization by postannealing yielded polycrystalline LN for LN film on amorphous ITO, but with a substantial number of c-axis oriented domains. For both amorphous LN film on polycrystalline TiN and polycrystalline ITO, however, nucleation assisted by seeds at the interface resulted in a completely random orientation.