Epitaxial BaTiO3 on Si(100) with In-Plane and Out-of-Plane Polarization Using a Single TiN Transition Layer

The integration of BaTiO3 with Si(100) is essential to exploit its ferroelectric capabilities in the well-established Si-complementary metal-oxide-semiconductor (CMOS) technological platform. To enable this goal, epitaxial BaTiO3 films with both in-plane and out-of-plane polarization are demonstrated on Si(100) with just a single TiN layer that is also CMOS-compatible. This change in polarization direction is brought about very simply by changing the growth temperature. Piezo force microscopy and optical second-harmonic generation measurements confirm the presence of out-of-plane and in-plane polarization. Films deposited at relatively higher temperatures of 800 degrees C have polarization lying in-plane at room temperature. The nonlinear dielectric susceptibilities were found to be comparable to the state-of-the-art films integrated with more complex transition schemes. Films deposited at a relatively lower temperature of 600 degrees C are defective and revert to 800 degrees C like films on annealing. The defects however confer on them an out-of-plane polarization with a large tetragonality of 1.6% at 500 degrees C. The changes in anomalous lattice expansion in outof-plane coupled with coefficient of thermal expansion (CTE) strain result in orientation selection in our films.

Automated summary

The study focuses on the polarization characteristics of BaTiO3 films grown on Si(100) substrates, demonstrating a polarization direction transition from in-plane to out-of-plane by changing the growth temperature. Films grown at 800 degrees Celsius exhibit in-plane polarization at room temperature, while films grown at 600 degrees Celsius with defects exhibit out-of-plane polarization at 500 degrees Celsius.