Lanthanide-Assisted Deposition of Strongly Electro-optic PZT Thin Films on Silicon: Toward Integrated Active Nanophotonic Devices

Abstract

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 Ln 2 O 2 CO 3 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.

Expanding the Silicon Photonics Portfolio With Silicon Nitride Photonic Integrated Circuits

“…An alternative route applicable to both SOI and SiN is to overlay the waveguide with a strong electro-refractive or electroabsorptive cladding layer. Results have been reported for graphene [101], for poled polymers [102], for ferro-electric materials [103] and for ABC-metamaterials [104], [105].…”

Effect of intrinsic point defects on ferroelectric polarization behavior of SrTiO3

“…Switchable polarization in ferroelectric materials due to the orientation of dipoles by an external electric field is central to various energy and information storage technologies including sensors and actuators [1], electro-optic devices [2][3][4], and ferroelectric field-effect transistors for nonvolatile memories [5,6]. In past years it has been revealed that ferroelectric polarization is not exclusive to polar materials and can be induced throughout the nonferroelectric layer of the heterostructure by combining a nonferroelectric oxide such as SrTiO 3 with a ferroelectric oxide, e.g., BaTiO 3 [7], or even with another nonferroelectric oxide, e.g., LaCrO 3 [8].…”

Ferroelectric thin films with liquid crystal for gradient index applications

“…Recently our group demonstrated that highly textured PZT thin films can be deposited on glass substrates using a cheap solution-based deposition method [18]. The process leads to a highquality polycrystalline layer as shown in Fig.…”

“…A 10 nm thin buffer layer is deposited on the glass substrate and the electrodes to ensure good crystal growth of the PZT, which is the next layer in the stack and is about 0.84 µm thick. The minimally required thickness of this buffer layer was determined experimentally [18], while the thickness of the PZT layer was chosen as a compromise between processing time and the required amount of electric field averaging as predicted by the simulations. On top of the PZT layer is a thin polyimide (PI) alignment layer, which is in contact with the nematic liquid crystal.…”