Low Temperature Epitaxial Barium Titanate Thin Film Growth in High Vacuum CVD

Abstract

Barium titanate is a promising perovskite material, exhibiting numerous materials properties advantageous for a range of applications, such as ferroelectricity, piezoelectricity, a high dielectric constant, and large electrooptic coefficients. It represents a potential candidate for the implementation of high bandwidth and low energy consuming modulators for optical communication in future integrated systems. Integration of the optical components with electronic circuits on silicon requires, however, suitable low temperature deposition processes for the growth of high quality epitaxial BaTiO3 films, which are still missing. For integration of novel materials into the complementary metal–oxide–semiconductor platform, a variety of prerequisites must be fulfilled; among them there is a strict limitation of the thermal budget of the growth process. Furthermore, high growth rates are desirable for enhanced throughput. Many chemical vapor deposition (CVD) processes allow growing thin films at high rates, but epitaxial BaTiO3 film formation typically requires high substrate temperatures. It is demonstrated that high vacuum CVD is capable of growing epitaxial barium titanate films on magnesium oxide, strontium titanate, and strontium titanate buffered silicon substrates at process temperatures of 400 °C and growth rates of up to 100 nm h−1 without the need of an additional annealing step; this is the lowest substrate temperature reported for a CVD processes.