ZrO2 Substrates Research Articles

Structural, optical and electrical properties of ternary Al2xIn2−2xO3 films prepared by MOCVD

Al2xIn2−2xO3 films with different xvapor values [Al/(Al+In) precursor input ratios] have been deposited on Y-stabilized ZrO2 (111) substrates by metal organic chemical vapor deposition (MOCVD) at 600°C. The influence of different Al contents (xvapor=0.1–0.9) on the structural, optical and electrical properties of the films was investigated in detail. A phase transition from the bixbyite In2O3 structure with a single orientation along (111) to the amorphous structure was observed for the films with the increase of xvapor value from 0.1 to 0.9. The average transmittances in the visible range for the Al2xIn2−2xO3 films were all over 77% and the optical band gap of the films varied from 3.64 to 4.81eV. The lowest resistivity of 9×10−3Ωcm, a carrier concentration of 8.2×1019cm−3 and a Hall mobility of 8.5cm2V−1s−1 were obtained for the film with xvapor=0.2.

Granular and layered ferroelectric–ferromagnetic thin-film nanocomposites as promising materials with high magnetotransmission effect

Epitaxial thin films of granular and layered nanocomposites consisting of ferromagnetic perovskite Pr1–xSrxMnO3 and ferroelectric hexagonal LuMnO3 were grown on ZrO2(Y2O3) substrates using metal-organic chemical vapor deposition (MOCVD). A self-organized growth of the granular composite took place in situ as a result of phase separation of the Pr–Sr–Lu–Mn–O system into the perovskite and hexagonal phases. Optical transmission measurements revealed a large negative magnetotransmission effect in the layered nanocomposite over a wide spectral and temperature range. The granular nanocomposite unexpectedly showed an even larger, but positive, magnetotransmission effect at room temperature.

Oriented PrBaCo2O5+δ thin films for solid oxide fuel cells

Oriented PrBaCo2O5+δ (PBC) thin films are prepared on yttria-stabilized ZrO2 (YSZ) substrates with orientations (001), (110) and (111) via pulsed laser deposition (PLD). Electrochemical impedance spectroscopy (EIS) experiments at various temperatures and oxygen partial pressures reveal a good oxygen reduction reaction (ORR) performance of all the thin films. However, the films' performance has considerable variance. PBC thin film deposited on (111) oriented YSZ had the best performance, followed by (110) and (001). Experiments including high resolution X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and computation, namely molecular dynamics (MD), are used to elucidate the substrate-determined orientations, examine the morphology and composition of the thin films, and to explain the variance of the ORR performance. Our results support the anisotropy of the oxygen vacancy pathway in the a–b plane and indicate that the substrate orientations can have great influence on the thin films properties.

Epitaxial Fe/Y2O3 interfaces as a model system for oxide-dispersion-strengthened ferritic alloys

The fundamental mechanisms underlying the superior radiation tolerance properties of oxide-dispersion-strengthened ferritic steels and nanostructured ferritic alloys are poorly understood. Thin film heterostructures of Fe/Y2O3 can serve as a model system for fundamental studies of radiation damage. Epitaxial thin films of Y2O3 were deposited by pulsed laser deposition on 8% Y:ZrO2 (YSZ) substrates with (100), (110), and (111) orientation. Metallic Fe was subsequently deposited by molecular beam epitaxy. Characterization by X-ray diffraction and Rutherford backscattering spectrometry in the channeling geometry revealed a degree of epitaxial or axiotaxial orientation for Fe(211) deposited on Y2O3(110)/YSZ(110). In contrast, Fe on Y2O3(111)/YSZ(111) was fully polycrystalline, and Fe on Y2O3(100)/YSZ(100) exhibited out-of-plane texture in the [110] direction with little or no preferential in-plane orientation. Scanning transmission electron microscopy imaging of Fe(211)/Y2O3(110)/YSZ(110) revealed a strongly islanded morphology for the Fe film, with no epitaxial grains visible in the cross-sectional sample. Well-ordered Fe grains with no orientation to the underlying Y2O3 were observed. Well-ordered crystallites of Fe with both epitaxial and non-epitaxial orientations on Y2O3 are a promising model system for fundamental studies of radiation damage phenomena. This is illustrated with preliminary results of He bubble formation following implantation with a helium ion microscope. He bubble formation is shown to preferentially occur at the Fe/Y2O3 interface.

Thin films of the spin ice compound Ho2Ti2O7

The pyrochlore compounds Ho2Ti2O7 and Dy2Ti2O7 show an exotic form of magnetism called the spin ice state, resulting from the interplay between geometrical frustration and ferromagnetic coupling. A fascinating feature of this state is the appearance of magnetic monopoles as emergent excitations above the degenerate ground state. Over the past years, strong effort has been devoted to the investigation of these monopoles and other properties of the spin ice state in bulk crystals. Here, we report the fabrication of Ho2Ti2O7 thin films using pulsed laser deposition on yttria-stabilized ZrO2 substrates. We investigated the structural properties of these films by X-ray diffraction, scanning transmission electron microscopy, and atomic force microscopy, and the magnetic properties by vibrating sample magnetometry at 2 K. The films not only show a high crystalline quality, but also exhibit the hallmarks of a spin ice: a pronounced magnetic anisotropy and an intermediate plateau in the magnetization along the [111] crystal direction.

Fabrication of hydroxyapatite thin films on zirconia using a sputtering technique.

Hydroxyapatite (HA) thin films were prepared on a zirconia (ZrO2) substrate using a sputtering technique, and the film was also coated on a titanium (Ti) substrate for comparison. The coated films were recrystallised using a hydrothermal treatment to reduce film dissolution. The films were then characterised by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The osteocompatiblity of the films was evaluated by investigating the alkaline phosphatase (ALP) activity and the size of the bone formation area of osteoblast cells. In the XRD patterns of the as-sputtered films on the ZrO2 substrate, there are no peaks except for those from the ZrO2 substrate. After the hydrothermal treatment, HA peaks appeared in the patterns. Nanoparticles (less than 20 nm) were observed on the ZrO2 substrates in the SEM images of the as-sputtered films. After the hydrothermal treatment, particles of 20-40 nm were observed on the film, whereas the HA film on the Ti substrate was covered by a larger number of globular particles (20-60 nm). In the osteoblast cell cultures, the ALP activity and bone formation area on the HA films on both the ZrO2 and Ti substrates increased after the hydrothermal treatment of the films, and the values for the ZrO2 substrate were higher than those for the Ti substrate.

Impact of the Substrate Material on the RF Performance of Carbon-Nanotube Transistors

We examine the effect of the substrate material on the radio-frequency (RF) behavior of carbon-nanotube transistors by considering the impact of substrate polar phonons (SPPs). We consider SPP scattering from AlN, SiO <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{2}$</tex></formula> , HfO <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{2}$</tex></formula> , and ZrO <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{2}$</tex></formula> substrates within a semiclassical approach by solving the time-dependent Boltzmann transport equation self-consistently with the Poisson equation. Various RF figures of merit, such as the unity-current gain frequency <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$f_T $</tex></formula> , the unity-power-gain frequency <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$f_{{\rm max}} $</tex></formula> , the transconductance <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$g_m $</tex></formula> , and the two-port <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$y$</tex></formula> -parameters, are determined in order to characterize the impact of SPP scattering. We first consider the impact of SPP scattering on the RF behavior of an intrinsic single-tube carbon nanotube field-effect transistor (CNFET). These single-tube results are then combined with the external parasitic elements to analyze the pitch-dependent, RF behavior of an extrinsic array-based CNFET. It is shown that AlN substrates have the least impact in degrading the RF performance of a CNFET, while the more polar substrates (HfO <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{2}$</tex></formula> or ZrO <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{2}$</tex> </formula> ) have a greater impact. This varying behavior can be attributed to the SPP energies, which are higher in AlN compared to the other materials, making CNFETs with AlN substrates less susceptible to SPP scattering even at room temperature. Our results suggest that substrate engineering will become an important component in the design process of emerging devices to achieve an optimized RF performance.

Growth of polycrystalline nickel hydroxide films from aqueous solution. Solution chemistry, deposition methods, film morphology and texture

Deposition of functional ceramic films on different substrates by using soft aqueous solution processing can represent a cheap, low- energy and environmental friendly alternative to other film technologies. In this study β-Ni(OH)2 polycrystalline films were grown on polytetrafluoroethylene, NiO, glass, copper, and Y:ZrO2 substrates from Ni2+–NH4OH aqueous solutions. A careful control of solution supersaturation was essential to induce heterogeneous nucleation on the substrate and film growth. This was realized through the gradual decomposition of the nickel amino complexes Ni(NH3)n2+ using two different methods. Thermodynamic modeling of the Ni–NH4OH–H2O system was used to provide some general indications for defining the experimental conditions most suitable for film deposition and understanding the role of solution chemistry on film formation. Film microstructure and texture can be controlled by varying the substrate, the ammonia concentration, the ammonia evaporation rate, the soaking time and by adding a surfactant like sodium dodecylbenzensulphonate. As a result, films with different morphologies and orientations, as well as a uniform decoration of the substrate surface with Ni(OH)2 crystals, were obtained. The proposed method can be extended to the preparation of oxide and hydroxide films of other transition metals forming moderately stable amino complexes.

Epitaxial growth of indium oxyfluoride thin films by reactive pulsed laser deposition: Structural change induced by fluorine insertion into vacancy sites in bixbyite structure

InOxFy thin films were epitaxially grown on Y-stabilized ZrO2 (111) substrates by reactive pulsed laser deposition. By changing the substrate temperature (TS), we were able to control the fluorine content of the film. Phase-pure epitaxial thin films with bixbyite-like ordering in the anion-site occupancy were obtained at high TS (≥240°C), where fluorine was inserted into the vacancy sites in the bixbyite lattice up to y/(x+y)~0.3. By decreasing TS, y/(x+y) increased and the bixbyite-like ordering disappeared; simultaneously, fluorine-rich and fluorine-poor subphases emerged. The films grown at TS≤150°C were amorphous and exhibited higher optical absorbance and electrical resistivity than the epitaxial films.

Low voltage, high performance inkjet printed carbon nanotube transistors with solution processed ZrO2 gate insulator

High-performance single-walled carbon nanotube (SWCNT) thin-film transistors are fabricated by single-pass inkjet printing of SWCNTs on high-κ solution-processed ZrO2 gate dielectric. We demonstrate that an ultraviolet ozone treatment of the ZrO2 substrate is critical in achieving a uniform dispersion of sorted SWCNTs in the semiconducting channel. The resulting devices exhibit excellent performance with mobility and on/off current ratio exceeding 30 cm2 V−1 s−1 and 105, respectively, at low operating voltages (&amp;lt;5 V). The single-pass inkjet printing process demonstrated in this letter shows great promise as a reliable and scalable method for SWCNT based high performance electronics.

Probing the dead layer thickness and its effect on the structure and magnetic properties in La2/3Ca1/3MnO3 thin films

The microstructure of La2/3Ca1/3MnO3 films of 42-nm thickness, grown on (001) SrTiO3, (001) LaAlO3 and (001) Y-stabilized ZrO2 substrates, has been studied with considering the existence of surface/interface dead layers. The dead layer thickness deduced from X-ray reflectivity is in good agreement with that from transport property measurements. Due to the surface and interface layers, the spontaneous emergence of fully relaxed and coherently strained films is further demonstrated by grazing incidence X-ray diffraction. The smallest saturation magnetization and the largest coercive filed is obtained in La2/3Ca1/3MnO3 film grown on LaAlO3 substrate, which has the thickest dead layer thickness. Moreover, the effect of dead layer on the magnetic and transport properties of La2/3Ca1/3MnO3 film grown on Y-stabilized ZrO2 substrate has been carefully analyzed.

Preparation and Characterization of Pt/YSZ Electrode of Zirconia Oxygen Sensor

Electrode slurry made of Pt powder was brushed on both surfaces of the sintered ZrO2 substrate. And then the Pt electrodes were sintered under various temperatures. The microstructure of the surface of the electrodes was characterized by scanning electronic microscope. The electrochemical properties of the electrodes were investigated by electrochemical impedance spectroscopy (EIS). The results show that the sintered temperature of the electrode has a remarkable effect on the microstructure of the electrode and the Pt electrode show favorable electrochemical catalysis performance.

A fundamental study of infiltrated CeO2 and (Gd,Ce)O2 nanoparticles on the electrocatalytic activity of Pt cathodes of solid oxide fuel cells

A thin Pt skeleton with a well-defined porous structure prepared on Y2O3–ZrO2 (YSZ) substrate is used as template to study the effect of impregnated pure CeO2 and Gd-doped CeO2 (GDC) nanoparticles on the electrochemical activity of Pt electrodes and to minimize possible interactions between the infiltrated phase/solution and the porous skeleton structure. The results show that the activity of Pt cathodes is enhanced by the infiltration of 0.2mgcm−2 (6.2wt.%) CeO2 and GDC nanoparticles. For the O2 reduction reaction under open circuit and at low current region the promotion effect of infiltrated CeO2 and GDC nanoparticles is close, but under higher currents the infiltrated GDC exhibits a much higher electrocatalytic activity as compared to the infiltrated CeO2 for the O2 reduction reaction on the Pt electrodes. The high electronic conductivity and high oxygen vacancies of GDC nanoparticles under polarization or dc bias, as compared to that of pure CeO2 are most likely responsible for the high catalytic effect of GDC nanoparticles for the O2 reduction reaction on the Pt. This study demonstrates that the electrochemical performance of infiltrated nano-structured electrodes is fundamentally affected by the catalytic properties of infiltrated nanoparticles.

Three-dimensionally kinked high-conducting CoGe nanowire growth induced by rotational twinning

We have synthesized single-crystalline horizontal and free-standing monoclinic CoGe nanowire (NW) arrays on high-k dielectric Y-stabilized ZrO2 (110) substrates via a chemical vapor transport process without using any catalysts. Horizontal NWs are grown epitaxially on the substrate. Three-dimensionally (3D)-kinked NWs are grown from the tip of the horizontal NWs homoepitaxially initiated by rotational twinning. Electrical measurements show that both horizontal and 3D-kinked CoGe NWs have low resistivity. The 3D-kinked NWs as well as free-standing metallic CoGe NWs integrated on Y-stabilized ZrO2 substrates could find applications as effective on-chip interconnects and nanoelectrodes for highly integrated nanoelectronic devices and as platforms for fuel cells and as efficient catalysts.

Room temperature ferromagnetism in epitaxial In2O3 films with embedded nano-sized Fe3O4 columns

Epitaxial In2O3 films with embedded Fe3O4 oriented nanocolumns were deposited by pulsed laser deposition (PLD) on Y-stabilized ZrO2 (111) substrates. The resulting films show ferromagnetism at room temperature with strong magnetic anisotropy, which can be attributed to the presence of Fe3O4 nanocolumns. Magnetotransport measurements demonstrate a transition from negative magnetoresistance to positive magnetoresistance as the measuring temperature increases. Quantitative coincidence between the anomalous Hall resistivity as a function of the magnetic field and the magnetic hysteresis loop is observed at room temperature, indicating the spin polarization nature of carriers.

Effects of Sn doping on the morphology and properties of Fe-doped In2O3 epitaxial films

(Sn, Fe)-codoped In2O3 epitaxial films were deposited on (111)-oriented Y-stabilized ZrO2 substrates by pulsed laser deposition with constant Fe concentration and different Sn concentrations. The influence of Sn concentration on the crystal structure and properties of Fe-doped In2O3 ferromagnetic semiconductor films has been investigated systematically. Experimental results indicate that Sn doping can effectively reduce the surface roughness and suppresses breakup of the films into separated islands. At the same time, the optical band gap increases and the electrical properties improve correspondingly. However, although the carrier density increases dramatically with the Sn doping, no obvious change of the ferromagnetism is observed. This is explained by a modified bounded magnetic polaron model.

ZrO2 surface chemically coated with hyaluronic acid hydrogel loading GDF-5 for osteogenesis in dentistry

The objective of this study was to modify zirconium dioxide (ZrO2) with photo-cured hyaluronic acid hydrogel (pcHAgel), and to subsequently evaluate the bone regeneration potential of the modified ZrO2. In the present study, HA grafted onto a ZrO2 substrate was investigated for its biocompatibility and other properties. We describe the positive influences of ZrO2 surface-modified with pcHAgel (Zr-3) containing two different loads of growth and differentiation factor-5 (GDF-5) to aid new bone formation as compared to the same amount of BMP-2 (Zr-4–7). We characterized the Zr-3 for their surface morphology and chemical properties. Atomic force microscopy (AFM), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) showed that the pcHAgel was successfully grafted onto the ZrO2 surface. The sustained release of GDF-5 and BMP-2 were observed to occur in the Zr-4–7. In vitro cell tests showed a higher level of MG63 cell proliferation and differentiation on Zr-4–7 than on Zr-3. The Zr-3 is a good biomaterial to deliver osteogenic differentiation factors such as BMP-2 and GDF-5, and GDF-5 can be useful as an effective alternative to aid new bone formation as compared to BMP-2.

Development and characterization of glass matrix composites as porous coating film of a solid state reference electrode

For protection against leaching of the electrolyte reservoir of a solid state reference electrode a porous covering film was prepared and characterized. The porous covering film is based on a glass matrix composite and fired at 400 °C according to the thick-film-based structure of the reference electrode. Based on stability investigations on low sintering glasses in the range of pH 1.68 to pH 9.18 and in various concentrated potassium chloride solutions, a suitable zinc borate glass was selected. Using this glass and Al2O3 or ZrO2 oxide powders, various glass matrix composites were prepared and their sintering behavior was investigated in dependence on the amount of crystalline fraction up to 45 vol%. The shrinkage was measured by heating microscopy of powder compacts of cylindrical shape. In addition composite films on ZrO2 substrates screen-printed and at 400 °C fired were characterized in terms of their porosity by means of micro structural analysis and electrochemical deposition of copper. According to these investigations, suitable composites were selected as porous covering materials for the reference electrode and were tested therefore. The electrochemical characterization showed that the solid-state reference electrodes with porous covering films have a very good performance compared to conventional reference electrodes.

The adsorption mechanism of titanium-binding ferritin to amphoteric oxide

We investigated the origin of selective adsorption of titanium-binding ferritin (TBF), the outer surface of which is genetically modified with titanium-binding peptides (TBPs). By varying pH conditions (7–9), TBF adsorption behavior onto amphoteric and acidic oxide substrates was observed using atomic force microscopy, and the zeta potential of substrates was measured. This suggests that a TBP interacted with local charges such as O−, OH+, and OH2+ on substrates regardless of the constituent elements of the substrate, which makes it possible for TBF to adsorb on TiOX, ZrO2, Fe2O3, and SiO2 substrates despite the presence of an overall electrostatic repulsive force between TBF and the substrates. This also suggests that a surfactant, TWEEN20, can completely hamper attractive interaction between TBF and acidic oxide, but amphoteric oxide can withstand TWEEN20 interference.

Initial growth of Bi4 LaTi3 FeO15 thin films on SrTiO3, MgO and YSZ substrates

AbstractThe initial growth modes of Bi4LaTi3FeO15 thin films on (001) SrTiO3, (001) MgO and (001) Y:ZrO2 (YSZ) substrates are studied. Detailed crystal structure, microstructure and surface morphology characterizations substantiate that Bi4LaTi3FeO15 films grow on these substrates via three‐dimensional grain growth mode. The synthesized Bi4LaTi3FeO15 films on (001) MgO and (001) SrTiO3 substrates do have c‐axis epitaxial Aurivillius layered structure, and have relative smooth surface roughness. While films grown on (001) YSZ show the polycrystalline quality with large surface roughness. The different crystal quality of films grown on MgO/SrTiO3 and YSZ substrates is explained qualitatively by considering the different atomic surface structures of these substrates.