Growth and characterization of (Pb,La)(Zr,Ti)O 3 thin film epilayers on SrTiO 3-buffered Si(001)

Abstract

Ferroelectric Pb 0.92La 0.08Zr 0.4Ti 0.6O 3 (PLZT) thin films were deposited on SrTiO 3-buffered Si(001) substrate by on-axis radio frequency magnetron sputtering. X-ray diffraction analysis revealed epitaxial growth of monocrystalline PLZT films, with an (001) rocking curve full width at half maximum of ∼ 0.3°. φ-scans showed 45° in-plane orientation of the perovskite unit cell relative to that of silicon. The elemental composition of the thin film heterostructure was examined by Auger sputter depth profiling measurements. The recorded profiles suggest that the SrTiO 3 buffer layer serves not only as a template for epitaxial growth, but also as a barrier suppressing Pb–Si interdiffusion between the PLZT layer and the Si substrate. The surface roughness of the PLZT layer was measured at ∼ 4 nm for films with ∼ 500 nm thickness. Wavelength dispersions for the refractive index ( n) and the extinction coefficient ( k) were obtained from spectroscopic ellipsometry measurements, with n ∼ 2.48 at the main communication wavelength λ = 1550 nm and k < 0.001 for λ > 650 nm. Recorded polarization vs. electric field loops for the PLZT epilayer, with a SrRuO 3 electrode layer interposed between PLZT and SrTiO 3, showed a remnant polarization P r ≈ 40 µC/cm 2 and coercive field E c ≈ 100 kV/cm. These findings suggest that the sputter-deposited PLZT thin films retain the functional properties critical to ferroelectric and electro-optic device applications, also when integrated on a semiconductor substrate.