Yttria-stabilized Zirconia Buffer Layers Research Articles

Epitaxial films of metals from the platinum group (Ir, Rh, Pt and Ru) on YSZ-buffered Si(1 1 1)

In the present work we have grown twin-free single crystal metal films of iridium (Ir), rhodium (Rh), platinum (Pt) and ruthenium (Ru) on silicon (1 1 1) substrates via an yttria-stabilized zirconia (YSZ) buffer layer. A prerequisite for the realisation of heteroepitaxial metal films without additional texture components was the twin-free deposition of the YSZ films by pulsed laser deposition (PLD). For the metal films on top, a novel two-step growth process was applied with an extremely low deposition rate for the first 20 nm. For all metals, a drastic texture improvement by up to a factor of 9 could be observed compared to the oxide buffer layer. Minimum values were 0.18° (Ir) and 0.12° (Rh) for tilt and twist, respectively. For all four metals investigated, twin-free epitaxial films could be grown on YSZ/Si(1 1 1) whereas the twinning problem for platinum films was solved by decoupling the Pt-YSZ interface via an additional iridium interlayer. The grown metal/YSZ/Si(1 1 1) multilayer samples offer the possibility to integrate a variety of interesting nanostructures and functional materials on silicon. They are now available in 4 in wafer size.

Highly c-Oriented PbZr[sub 0.48]Ti[sub 0.52]O[sub 3] Thin Films on Glass Substrates

We obtained preferentially (220)-oriented yttria-stabilized zirconia (YSZ) buffer layers on glass substrates by pulsed laser deposition. These preferentially (220)-oriented YSZ buffer layers enabled us to grow preferentially (100)-oriented bottom electrodes. On the preferentially (100)-oriented bottom electrodes, we obtained preferentially -oriented (PZT) thin films, which were confirmed by an X-ray diffraction experiment. The highly -oriented PZT thin films exhibited a high ferroelectric polarization of about . We also checked a high storage density of about with a minimum bit size below with the highly -oriented PZT thin films by electric force microscope.

Growth of biepitaxial zinc oxide thin films on silicon (100) using yttria-stabilized zirconia buffer layer

In this work, an approach for integrating zinc oxide thin films with Si(100) substrates using an epitaxial tetragonal yttria-stabilized zirconia buffer layer is reported. Selected area electron diffraction measurements revealed the following epitaxial relationship: [110]YSZ∥[100]Si and (001)YSZ∥(001)Si. X-ray diffraction studies demonstrated that subsequent growth of the zinc oxide thin film on the yttria-stabilized zirconia buffer layer occurred with the following epitaxial relationship: (0002)ZnO∥(001)YSZ. The full width at half maximum value for the (0002) peak of zinc oxide was small (∼0.16°), which indicated good crystalline quality. Transmission electron microscopy revealed that the zinc oxide thin film grew epitaxially on an yttria-stabilized zirconia buffer layer in two different orientations, where one orientation was rotated by 30° from the other. The orientation relationship in this case was [101¯0]ZnO∥[100]YSZ or [21¯1¯0]ZnO∥[100]YSZ and (0002)ZnO∥(001)YSZ. The biepitaxial growth of the zinc oxide thin film has been explained in the framework of domain matching epitaxy. Optical emission measurements showed a strong excitonic emission peak from the zinc oxide thin film at ∼377 nm. Minimal green band emission in the photoluminescence spectrum indicated that the concentration of point defects was low. Integration of epitaxial zinc oxide thin films with Si(100) substrates is an important step toward developing practical applications of zinc oxide in a variety of optoelectronic devices.

Effects of ion energy on ion beam assisted deposition textured yttria stabilized zirconia buffer layer of coated conductor

High quality biaxially textured yttria stabilized zirconia (YSZ) thin films, as buffer layers of coated conductors, were deposited on hastelloy substrates by ion beam assisted deposition (IBAD) method with different assisting ion energy E i. The roles of assisting ion beam and the influences of ion energy E i on the structure of the films were studied. It was found that both the out-of-plane alignment and in-plane texture of the IBAD-YSZ films are sensitive to the variation of E i. The results are explained in the paper by different damage tolerance of the differently oriented grains to ion bombardment.

Epitaxial Growth of Ferromagnetic Iron Silicide Thin Films on Silicon with Yttria-Stabilized Zirconia Buffer Layer

(110)-oriented epitaxial Fe3Si films were grown on (100) and (111) Si substrates with an epitaxial yttria-stabilized zirconia (YSZ) buffer layer by rf-magnetron sputtering. The epitaxial Fe3Si films contained a two-domain structure on the (100) substrate with a YSZ buffer layer, and a three-domain structure on the (111) substrate with a YSZ buffer layer. The coercive forces (Hc) of both epitaxial films were each approximately 40 Oe, and the saturation magnetizations (Ms) were each 850 emu/cm3, which are almost at the same level as those of bulk Fe3Si.

Reduction of mosaic spread using iridium interlayers: A route to improved oxide heteroepitaxy on silicon

Using epitaxial SrTiO3 and yttria-stabilized zirconia (YSZ) buffer layers deposited on silicon as a starting point, epitaxial iridium layers were grown by electron-beam evaporation using a two-step growth process with an extremely low initial deposition rate. The iridium layers had in-plane (twist) and out-of-plane (tilt) full widths at half maximum as narrow as 0.08° and 0.15°, respectively, up to an order of magnitude narrower than the underlying SrTiO3 and YSZ layers. SrTiO3 and ZnO films grown on the iridium showed significantly narrower twist and tilt values than without the iridium interlayer, demonstrating a route to improved oxide heteroepitaxy on silicon.

Buffer-Enhanced Electrical-Pulse-Induced Resistive Memory Effect in Thin Film Perovskites

A multilayer perovskite thin-film resistive memory device composed of a Pr0.7Ca0.3MnO3 (PCMO) perovskite oxide epitaxial layer on a YBa2Cu3O7-δ (YBCO) thin-film bottom electrode, a thin yttria-stabilized zirconia (YSZ) buffer layer grown on the PCMO layer, and a gold thin-film top electrode has been developed. With the addition of the YSZ buffer layer, the pulse voltage needed to switch the device is significantly reduced and the resistance-switching ratio is increased compared to a non buffered resistive memory device, which is very important for device fabrication. The magnetic field effect on the multilayer structure resistance at various temperatures shows colossal magnetoresistance (CMR) behavior for both high and low resistance states, implying a bulk material component in the switch behavior. The multilayer thin-film lattice structure has been further characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses, which indicate a high-quality heterostructure. Current imaging atomic force microscopy (I-AFM) analysis indicated nanogranular conductivity distributed uniformly throughout the PCMO film surface.

Investigation of the strain relaxation and ageing effect ofYBa2Cu3O7−δ thin films grown on silicon-on-insulator substrates with yttria-stabilized zirconia bufferlayers

The integration of high-temperature superconductors into advanced semiconductortechnology is rather intriguing in the microelectronics field. In this paper, we report onYBa2Cu3O7−δ (YBCO) thin films deposited on silicon-on-insulator (SOI) substrates buffered byyttria-stabilized zirconia (YSZ) layers using the in situ pulsed laser deposition (PLD)technique. The strain in the YBCO films and the ageing effect caused by the thermallyinduced cracks are carefully studied. It is believed that because of the adoption of the SOIsubstrate, the strain in the YBCO films is greatly relaxed and the quality and stability ofYBCO films are rather good, which is advantageous to the superconductive devices.

Stress Control and Ferroelectric Properties of Lead Zirconate Titanate (PZT) Thin Film on Si Substrate with Buffer Layers

Lead zirconate titanate (PZT) thin films were grown on a Si substrate with an epitaxial relationship by introducing yttria-stabilized zirconia (YSZ), CeO2, and (La,Sr)CoO3 (LSCO) buffer layers. The buffer layers, which facilitated the growth of the epitaxial PZT thin film and controlled the residual stress, were deposited by pulsed laser deposition (PLD). The PZT thin films were fabricated on [A]: LSCO*/CeO2/YSZ/Si and [B]: LSCO*/PZT*/LSCO/CeO2/YSZ/Si by pulsed metalorganic chemical vapor deposition. The respective thicknesses of the LSCO* and PZT* layers were changed to control the residual stress in the PZT thin films. The relationship between residual stress and the ferroelectric properties of the PZT thin films was investigated. Residual tensile stresses in the PZT thin films were maximum in [A] as LSCO* thickness changed. Increasing the PZT* layer thickness at a fixed thickness of LSCO* of 188 nm changed the residual tensile stress in the PZT thin films from 2.92 GPa to 2.67 GPa. Consequently, remanent polarization (2Pr) was increased from 15 µC/cm2 to 27 µC/cm2, suggesting that residual stress may be controlled by introducing buffer layers and that ferroelectric properties may be improved.

Flexible Y Ba2Cu3O7−δ-coated superconductor tapes on non-metallic substrates with spin-on-glass and IBAD-YSZbuffer layers

Non-metallic flexible Y Ba2Cu3O7−δ (YBCO)-coated superconductor tapes were fabricated using zirconia with 3 mol% yttriaCERAFLEXTM (CF) substrates. The CF substrate surface was treated by spin-coating of spin-on-glass (SOG).Yttria-stabilized zirconia (YSZ) buffer layers were deposited on the SOG layer by ion beamassisted magnetron deposition (IBAD). The epitaxial YBCO films were grown on the bufferlayer. The crystalline quality and degree of biaxial alignment were measured using the x-rayθ–2θ andϕ-scans. The YBCO filmswere c-axis aligned andhad an YBCO(103) ϕ-scan full width half maximum (FWHM) of10.5°. Films withϕ-scan FWHM of19° had a zero field criticalcurrent density, Jc, of 0.25 MA cm−2 at 77 K as measured by the induction method.

Substrate effect on low‐field transport properties of La–Pb–Mn–O granular‐type thin films

AbstractThis paper studied the low‐field tunnel‐type transport characteristics of polycrystalline and c‐axis‐oriented La0.7Pb0.3MnO3 (LPMO) thin films. Polycrystalline thin films were fabricated on SiO2/Si(100) substrate (film A), on SiO2/Si substrate with yttria‐stabilized zirconia (YSZ) buffer layer (film B), and on c‐axis‐oriented thin film grown on LaAlO3(001) (LAO) single crystal substrate (film C) using the soft‐chemical deposition method. A YSZ buffer layer acts as a barrier against inter‐diffusion. As a result, it decreases the amount of dead layers generated from the interface and helps to produce qualitative films for application of magnetoresistive elements. The magnetoresistance (MR) ratio was 0.52%, 0.7%, and 0.4% for film A, film B, and film C under the applied field of 500 Oe at 300 K, respectively. The polycrystalline film had denser boundaries than the c‐axis oriented film, i.e., the polycrystalline film gave more effective potential barrier regions than the c‐axis oriented film. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

High critical current density of YBCO coated conductors fabricated by inclined substrate deposition

Inclined substrate deposition (ISD) has great potential for rapid production of high-quality template layers for YBCO-coated conductors. We have grown biaxially textured magnesium oxide (MgO) films on metallic substrates by ISD at deposition rates, 20–100 Å/s. Scanning electron microscopy of the ISD MgO films showed columnar grain structures with a roof-tile-shaped surface. X-ray diffraction and pole figure analysis revealed that the c-axis of the ISD MgO is tilted at an angle with respect to the substrate normal. A full width at half maximum (FWHM) of ≈10° was observed in the φ-scan for MgO films. Yttria-stabilized zirconia (YSZ) and ceria (CeO 2) buffer layers were epitaxially grown on ISD MgO by pulsed laser deposition (PLD) prior to YBCO deposition by PLD. The YBCO films grown on YSZ/CeO 2 buffered ISD MgO substrates were biaxially aligned with the YBCO c-axis normal to the substrate surface. A critical current density of J c>1.2×10 6 A/cm 2 was measured at 77 K in self-field.

Proposal of general rule to prepare epitaxial ceramic thin films at low temperature from the point of crystal chemistry

We have succeeded to prepare epitaxial yttria stabilized zirconia (YSZ) thin films at room temperature (27 °C) by the use of nm thick YSZ buffer layer deposited at 800 °C on Si(0 0 1) substrate. Room temperature epitaxial growth was realized on 0.8 nm thick ultra thin YSZ buffer layer, however, to achieve high crystallinity, 6.7 nm thick was needed. On the 6.7 nm thick YSZ buffered Si(0 0 1) substrate, we have tried to prepare epitaxial oxide ceramic thin films. As the result, epitaxial CeO 2, In 2O 3, and MnZn-ferrite thin films were successfully deposited even at room temperature. The conditions of epitaxial growth at such low temperature was considered from the point of crystal chemistry. As the result, following conditions were proposed: (1) Materials with both small lattice mismatch and small electronegativity difference; or (2) Materials with small lattice mismatch and composed of single component. These proposed conditions will helpful to design epitaxial growth of oxide ceramic thin film at low temperature.

Analysis of coplanar LiNbO3 waveguide structures applicable to electrooptic modulator with FDTD method

AbstractThe 3D finite‐difference time‐domain (FDTD) method and the 2D quasi‐static formulation have been used to calculate the characteristic impedance and the microwave effective index of coplanar waveguide structures on lithium niobate (LiNbO3) single‐crystal substrates with a yttria‐stabilized zirconia (YSZ) or SiO2 buffer layer. The results shown can be a good source to predict the modulator characteristics. The effects of the thin buffer layer and anisotropy of the LiNbO3 crystal (x‐cut and z‐cut) are discussed. The comparison between the FDTD and quasi‐static results shows good agreement. In this paper, the efficient modeling technique of the FDTD method for the coplanar waveguide (CPW) structures based on an anisotropic substrate with a thin buffer layer is developed. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 234–237, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11178

Fabrication of YSZ buffer layer by single source MOCVD technique for YBCO coated conductor

Yttria stabilized zirconia (YSZ) buffer layers were deposited by a metal organic chemical vapor deposition technique using a single liquid source for the application of YBa 2Cu 3O 7− δ (YBCO) coated conductor. Y:Zr mole ratio was 0.2:0.8, and tetrahydrofuran (THF) was used as a solvent. The (1 0 0) single crystal MgO substrate was used for searching the deposition conditions. Bi-axially oriented CeO 2 and NiO films were fabricated on {1 0 0} 〈0 0 1〉 textured Ni substrate by the same method and used as templates. At a constant working pressure of 10 Torr, the deposition temperatures (660–800 °C) and oxygen flow rates (100–500 sccm) were changed to find the optimum deposition condition. The best (1 0 0) oriented YSZ film on MgO was obtained at 740 °C and O 2 flow rate of 300 sccm. For a YSZ buffer layer with this deposition condition on a CeO 2/Ni template, full width half maximum values of the in-plane ( ϕ-scan) and out-of-plane ( ω-scan) alignments were 10.6° and 9.8°, respectively. The SEM image of YSZ film on CeO 2/Ni showed surface morphologies without microcracks. The film deposition rate was about 100 nm/min.

New approach to depositing yttria-stabilized zirconia buffer layers for coated conductors

A new approach for the production of yttria-stabilized zirconia (YSZ) oxide buffer layers directly on metal rolling-assisted biaxially textured substrates (RABiTS) is described in this paper. This represents a significant advance over existing techniques and avoids the need for complicated steps to avoid substrate oxidation during direct deposition of oxides. Current densities of about 1 MA/cm2 have been achieved for YBa2Cu3O7-δ layers on the YSZ buffer, with an intermediate CeO2 layer. The process consists of reactive sputtering of a YxZr1−xN film directly on the RABiTS, which adopts its biaxial texture. This nitride film is then converted to YSZ via a thermal oxidation step. The YSZ films retain the texture of the nitride film (and of the RABiTS) through local syntaxy. In many cases, YSZ films exhibit improved biaxial texture over that of the RABiTS substrate. Nitrides can be sputter deposited at much higher rates relative to oxides, making the approach industrially scalable and economical.

YSZ buffer layers and YBCO superconducting tapes with enhanced biaxial alignment and properties

Commercial applications of YBa 2Cu 3O 7 (YBCO) superconducting cables require viable and scalable manufacturing processes. We have investigated the evolution of the biaxial alignment of yttria-stabilized zirconia (YSZ) buffer layers with increasing film thickness (50–900 nm) and report on a method of fabricating highly aligned YBCO tapes using a thin epitaxial YSZ buffer layer as template. The method employs magnetron and ion beam assisted deposition (IBAD) techniques followed by epitaxial growth to produce the buffer architectures IBAD-YSZ and epi-YSZ/IBAD-YSZ onto optically polished hastelloy metal substrates. Subsequent in situ deposition of YBCO films is used to determine the biaxial alignment at the surface of the buffer architecture, and to show that 100–200 nm thick epi-YSZ layers suffice to yield YBCO tapes that have enhanced biaxial alignment (Δ φ=9–10°) and high critical current densities: J c (77 K)=(1–2)×10 6 A cm −2 and J c (5 K,1 T)=8×10 6 A cm −2. Atomic force microscopy of the surface microstructure of the YSZ buffer layers and YBCO films reveals some grain coarsening in the epi-YSZ layers compared to the IBAD-YSZ layers while the YBCO tapes show significant outgrowths (∼200 nm) and large grains (800–1200 nm) that are similar to high- J c YBCO films grown on single crystal MgO(1 0 0) substrates.

Pulsed laser deposition of YBCO films on ISD MgO buffered metal tapes

Biaxially textured magnesium oxide (MgO) films deposited by inclined-substrate deposition (ISD) are desirable for rapid production of high-quality template layers for YBCO-coated conductors. High-quality YBCO films were grown on ISD MgO buffered metallic substrates by pulsed laser deposition (PLD). Columnar grains with a roof-tile surface structure were observed in the ISD MgO films. X-ray pole figure analysis revealed that the (002) planes of the ISD MgO films are tilted at an angle from the substrate normal. A small full-width at half maximum (FWHM) of ≈9° was observed in the ϕ-scan for ISD MgO films deposited at an inclination angle of 55°. In-plane texture in the ISD MgO films developed in the first ≈0.5 μm from the substrate surface, and then stabilized with further increases in film thickness. Yttria-stabilized zirconia and ceria buffer layers were deposited on the ISD MgO grown on metallic substrates prior to the deposition of YBCO by PLD. YBCO films with the c-axis parallel to the substrate normal have a unique orientation relationship with the ISD MgO films. An orientation relationship of YBCO⟨100⟩∥MgO⟨111⟩ and YBCO⟨010⟩∥MgO⟨110⟩ was measured by x-ray pole figure analyses and confirmed by transmission electron microscopy. A Tc of 91 K with a sharp transition and transport Jc of 5.5 × 105 A cm−2 at 77 K in self-field were measured on a YBCO film that was 0.46 μm thick, 4 mm wide and 10 mm long.

Texture and surface morphology of yttria-stabilized zirconia buffer layer on Ni-based tapes by electron beam evaporation

Biaxially textured buffer layers of yttria-stabilized zirconia (YSZ) have been fabricated on metal Ni-based tapes by electron beam evaporation technique. The high deposition rate of the electron beam evaporation presents an advantage in making long coated tape. Various materials including cubic textured Ni, Cu–Ni, and Hastelloy tapes were used as substrates. The grown YSZ films were characterized by X-ray diffraction, scanning electron microscopy, etc. It was found that the YSZ buffer layers were highly c-axis oriented on Ni or Ni-based tapes. The YSZ (1 1 1) pole figure revealed a cubic texture. The full width at half maximum of ϕ-scan of YSZ (1 1 1) deposited on Ni, Cu–Ni, and Hastelloy tapes was 15°, 14° and 20°, respectively. The surface of YSZ film is dense. Such YSZ buffer layers are promising for making YBCO coated conductors on metal tapes.

Fabrication of SrRuO3 Epitaxial Thin Films on YBa2Cu3Ox / CeO2 / YSZ - Buffered Si Substrates by Pulsed Laser Deposition

ABSTRACTPseudocubic SrRuO3 (100) epitaxial thin films were fabricated on Si (100) with a YBa2Cu3Ox / CeO2 / YSZ (yttria-stabilized-zirconia) triple buffer layer ∼ 14 nm thick by pulsed laser deposition (PLD). Reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD) revealed that the first buffer layer of YSZ (100) was epitaxially grown on naturally oxidized Si (100) substrates with the process condition of PB (base pressure) = 1×10-Torr, PO2 (oxygen partial pressure) = 5×10- Torr, and Ts (substrate temperature) = 700 °C. Higher deposition rate of YSZ in the range of 0 ∼ 0.6 nm/min brought about better crystallinity with a smaller value of a full-width at half maximum (FWHM) in the YSZ (200) rocking curve. Subsequent deposition of CeO2, YBa2Cu3Ox, and SrRuO3 resulted in an SrRuO3 (100) epitaxial thin film exhibiting good crystallinity with FWHM = 1.7° in the SrRuO3 (200) rocking curve.