Single-crystal Pb(ZrxTi1−x)O3 thin films prepared by metal-organic chemical vapor deposition: Systematic compositional variation of electronic and optical properties

Abstract

Single-crystal thin films of Pb(ZrxTi1−x)O3 (PZT) covering the full compositional range (0⩽x⩽1) were deposited by metal-organic chemical vapor deposition. Epitaxial SrRuO3(001) thin films grown on SrTiO3(001) substrates by rf-magnetron sputter deposition served as template electrode layers to promote the epitaxial growth of PZT. X-ray diffraction, energy-dispersive x-ray spectroscopy, atomic force microscopy, transmission electron microscopy, and optical waveguiding were used to characterize the crystalline structure, composition, surface morphology, microstructure, refractive index, and film thickness of the deposited films. The PZT films were single crystalline for all compositions exhibiting cube-on-cube growth epitaxy with the substrate and showed very high degrees of crystallinity and orientation. The films exhibited typical root mean square surface roughness of ∼1.0–2.5 nm. For tetragonal films, the surface morphology was dominated by grain tilting resulting from ferroelectric domain formation. We report the systematic compositional variation of the optical, dielectric, polarization, and electronic transport properties of these single-crystalline PZT thin films. We show that the solid-solution phase diagram of the PZT system for thin films differs from the bulk due to epitaxy-induced strains and interfacial defect formation. High values of remanant polarization (30–55 μC/cm2) were observed for ferroelectric compositions in the range of 0.8⩽x⩽0.2. Unlike previous studies, the dielectric constant exhibited a clear dependence on composition with values ranging from 225 to 650. The coercive fields decreased with increasing Zr concentration to a minimum of 20 kV/cm for x=0.8. The undoped films exhibited both high resistivity and dielectric-breakdown strength (1013–1014 Ω cm at 100 kV/cm and 300–700 kV/cm, respectively).

Optical properties of PbTiO3, PbZrxTi1−xO3, and PbZrO3 films deposited by metalorganic chemical vapor on SrTiO3

“…Similar results were later found for MOCVD PZT films. 11 The measurements are in agreement at 633 nm for MOCVD films and ceramics but the reference on MOCVD films does not contain dispersion data. In Ref.…”

“…On the basis of published values of the refractive index versus PZT composition 8,11 as well as on the basis of our own measurements presented in this study, we calculated ͑⌬, ⌿͒ contours for a number of PZT compositions on STO substrates using a linear extrapolation between the refractive index and the x ratio with n PT ϭ(2.66,0.0) and n PZ ϭ(2.46,0.0) at ϭ633 nm. Such contours are shown in Fig.…”

“…The values of the refractive index are in very good agreement at 633 nm with reported values. 8,11,12,20 The zone-2 data were fitted by a Cauchy fit of the form…”

“…Three articles were found on PLZT ceramics and sol-gel films [8][9][10] and two on metalorganic chemical vapor deposition ͑MOCVD͒ PZT films. 11,12 In this article, we report on the optical properties of PZT films grown by MOCVD on STO. The PZT film composition studied spanned the full composition range from PT (xϭ0) to PZ (xϭ1).…”

Novel mesoscale defect structure on NiO(100) surfaces by atomic force microscopy

“…The surface properties of these materials, in turn, are often highly infl uenced by surface defect structure [1], [2], [3] and [4]. Defects have been shown to be important in TMO electronic, magnetic, and chemical properties and span a wide range of scale, including oxygen vacancies [1], [2], [3], [5], [6], [7] and [8], metal interstitials and adatoms [1] and [9], crystal shear planes [4] and [10], step-defects [4], [10], [11] and [12], meso-to macroscopic scale pits, protrusions, and related large-scale imperfections [13], [14] and [15], the latter of which often have a complicated morphology with a range of atomic-scale defects in their own right [16], [17], [18] and [19]. The surface defect nature may be infl uenced by bulk structure and impurity concentration [1], [4] and [20], introduced by surface preparation methods [12] and [21], or result from chemical reactivity and corrosion properties of the substrate surface [1], [2], [3], [5], [6] and [22].…”