| AVS 66th International Symposium & Exhibition | |
| Thin Films Division | Tuesday Sessions |
| Session TF+EM+MI-TuM |
| Session: | Thin Films for Microelectronics, Photonics, and Optoelectronic Applications |
| Presenter: | John G. Ekerdt, University of Texas at Austin |
| Authors: | J.G. Ekerdt, University of Texas at Austin B.I. Edmondson, University of Texas at Austin E. Lin, University of Texas at Austin S. Kwon, University of Texas at Dallas A.A. Demkov, University of Texas at Austin M.J. Kim, University of Texas at Dallas |
| Correspondent: | Click to Email |
Recent investigations into thin film BaTiO3 (BTO) show it is a promising candidate for on-chip photonic devices due to its large linear electro-optic (EO) coefficient (r > 100-1000 pm/V) relative to more conventional photonic materials such as LiNbO3 (~30 pm/V) or strained Si (~2 pm/V). However, such high coefficients are achieved only by costly and inherently un-scalable physical vapor deposition techniques. In recent studies, we have investigated chemical routes to the integration of electro-optically active BTO thin films with Si, which offer faster and more scalable methods of deposition. Specifically, atomic layer deposition (ALD) of 40 nm BTO films and chemical solution deposition (CSD) of 85 nm BTO films on SrTiO3 (STO) templates on Si (001) prepared by molecular beam epitaxy (MBE) yield epitaxial BTO films with microstructure and defect nature markedly different from physical deposition techniques. Furthermore, we explored CSD of c-axis in-plane BaxSr1-xTiO3, which is difficult to achieve by physical methods and offers unique insight into the EO behavior of this highly tunable dielectric. X-ray diffraction and scanning transmission electron microscopy confirmed epitaxial, distorted tetragonal structures with a range of structural defects, and electrical and electro-optical measurements showed diminished ferroelectricity and EO response compared to MBE-grown thin films or bulk BTO. ALD-grown films exhibited optical hysteresis with coercivity of ~10 kV/cm, an effective linear EO coefficient of 26 pm/V for 40 nm films, and leakage currents caused by oxygen vacancies. CSD-grown films did not show evidence of ferroelectric hysteresis but maintained EO response with a coefficient of 25 pm/V and had very low leakage current. Past reports of chemical vapor deposited films yielded an EO coefficient of 7 pm/V. These results provide further understanding into the relationship between film structure and linear EO behavior.