title: Lanthanide-Assisted Deposition of Strongly Electro-optic PZT Thin Films on Silicon: Toward Integrated Active Nanophotonic Devices.
abstract: The electro-optical properties of lead zirconate titanate (PZT) thin films depend strongly on the quality and crystallographic orientation of the thin films. We demonstrate a novel method to grow highly textured PZT thin films on silicon using the chemical solution deposition (CSD) process. We report the use of ultrathin (5-15 nm) lanthanide (La, Pr, Nd, Sm) based intermediate layers for obtaining preferentially (100) oriented PZT thin films. X-ray diffraction measurements indicate preferentially oriented intermediate Ln2O2CO3 layers providing an excellent lattice match with the PZT thin films grown on top. The XRD and scanning electron microscopy measurements reveal that the annealed layers are dense, uniform, crack-free and highly oriented (>99.8%) without apparent defects or secondary phases. The EDX and HRTEM characterization confirm that the template layers act as an efficient diffusion barrier and form a sharp interface between the substrate and the PZT. The electrical measurements indicate a dielectric constant of ∼650, low dielectric loss of ∼0.02, coercive field of 70 kV/cm, remnant polarization of 25 μC/cm(2), and large breakdown electric field of 1000 kV/cm. Finally, the effective electro-optic coefficients of the films are estimated with a spectroscopic ellipsometer measurement, considering the electric field induced variations in the phase reflectance ratio. The electro-optic measurements reveal excellent linear effective pockels coefficients of 110 to 240 pm/V, which makes the CSD deposited PZT thin film an ideal candidate for Si-based active integrated nanophotonic devices.
authors.affiliation: †Department of Electronics and Information Systems, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent, Belgium.|‡Department of Information Technology, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent, Belgium.|∥Center for Nano- and Biophotonics (NB-Photonics), Ghent University, 9000 Gent, Belgium.
authors.forename: J P
authors.initials: JP
authors.lastname: George
authors.affiliation: §LumiLab, Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, 9000 Gent, Belgium.|∥Center for Nano- and Biophotonics (NB-Photonics), Ghent University, 9000 Gent, Belgium.
authors.forename: P F
authors.initials: PF
authors.lastname: Smet
authors.affiliation: §LumiLab, Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, 9000 Gent, Belgium.|∥Center for Nano- and Biophotonics (NB-Photonics), Ghent University, 9000 Gent, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Botterman
authors.affiliation: ⊥Department of Materials Science and Engineering, Ghent University, Technologiepark 903, B-9052 Zwijnaarde, Belgium.
authors.forename: V
authors.initials: V
authors.lastname: Bliznuk
authors.affiliation: †Department of Electronics and Information Systems, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent, Belgium.|∥Center for Nano- and Biophotonics (NB-Photonics), Ghent University, 9000 Gent, Belgium.
authors.forename: W
authors.initials: W
authors.lastname: Woestenborghs
authors.affiliation: ‡Department of Information Technology, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent, Belgium.|∥Center for Nano- and Biophotonics (NB-Photonics), Ghent University, 9000 Gent, Belgium.
authors.forename: D
authors.initials: D
authors.lastname: Van Thourhout
authors.affiliation: †Department of Electronics and Information Systems, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent, Belgium.|∥Center for Nano- and Biophotonics (NB-Photonics), Ghent University, 9000 Gent, Belgium.
authors.forename: K
authors.initials: K
authors.lastname: Neyts
authors.affiliation: †Department of Electronics and Information Systems, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent, Belgium.|∥Center for Nano- and Biophotonics (NB-Photonics), Ghent University, 9000 Gent, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Beeckman
keywords: chemical solution deposition; dielectric; electro-optic effect; ellipsometry; lead zirconate titanate; modulator; pockels coefficient