ZrO2 Buffer Layer Research Articles

Influence of the thickness of ZrO2 buffer layer on the electrical and optical properties of VO2 films

In this study, high-quality thermochromic vanadium dioxide (VO2) thin films were grown on ZrO2/glass by pulsed laser deposition and were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), double beam spectrophotometry and Hall Effect measurement system. Based on XRD results, it can be inferred that the crystal structure of ZrO2 buffer layer can be transformed between monoclinic and tetragonal structures with the increase of buffer layer thickness. Photoelectric performance tests showed that the introduction of ZrO2 buffer layer considerably reduced the phase transition temperature (Tc) and hysteresis loop width (ΔH) of the VO2 films and allowed the visible light transmittance (Tlum) and solar modulation ability (ΔTsol) of the films to be tuned effectively. Especially, when the thickness of the ZrO2 buffer layer was 50 nm, the Tc of the VO2 films reached the minimum value of 48 °C. When the ZrO2 buffer layer thickness increased to 125 nm, the sheet resistance change of the VO2 film attained two orders of magnitude, and their Tlum-90°C and ΔTsol were as high as 50.01% and 7.88%, respectively. These results showed that the ZrO2 buffer layer considerably affected the growth of VO2 films on amorphous glass substrates and was beneficial for the application of VO2 in energy-saving smart windows.

Oxidation resistance improvement of Zr-4 alloy in 1000 °C steam environment using ZrO2/FeCrAl bilayer coating

A ZrO2/FeCrAl bilayer coating was prepared on Zr-4 alloy. Plasma electrolytic oxidation (PEO) was used to synthesize the ZrO2 buffer layer and magnetron sputtering was used to deposit the FeCrAl outer layer. The oxidation resistance of the ZrO2/FeCrAl coated Zr-4 alloy was investigated by using 1000 °C steam oxidation tests and was compared with the mono-layer FeCrAl coated and uncoted Zr-4 alloys. Morphologies, phase compositions and elemental distributions of the ZrO2/FeCrAl and FeCrAl coated Zr-4 alloys before and after the steam oxidation tests were characterized by SEM, XRD and EDX mapping and line scans. Results indicated that the introduction of the ZrO2 buffer layer effectively eliminated the high temperature inter-diffusion between FeCrAl and Zr-4 alloy, and consequently improved the adherence and integrity of the FeCrAl layer after the 1000 °C steam oxidation. As a result, the parabolic rate constant of the ZrO2/FeCrAl coated Zr-4 alloy was decreased by about 20 times compared with that of the uncoated and FeCrAl coated Zr-4 alloys in 1000 °C steam environment.

Effect of residual stress in Pb (Zr0.52Ti0.48) O3 – BiFeO3 multilayer cantilever structure

This paper discussed about the integration issues of Pb (Zr0.52Ti0.48) O3 – BiFeO3 (PZT - BFO) multilayer thin film deposited on silicon substrate for possible application in future micro-electro-mechanical system (MEMS) devices. The PZT - BFO multilayer thin film is deposited on silicon wafer by sol-gel technique. The multilayer film is annealed at 650 °C in air for 60 min. The deposited multilayer film is found to be polycrystalline in nature. The PZT-BFO multilayer exhibited room temperature multiferroic properties (remnant polarization of 37 mC/ cm 2 and remnant magnetization of 3.1 emu / cm 3 ). To fabricate the PZT - BFO multiferroic cantilever structures, a two-mask process flow is developed. Etch rates of the PZT - BFO multilayer (180 nm/ min), ZrO2 buffer layer (35 nm/ min) and SiO2 layer (350 nm/ min) are optimized in CHF3 plasma. The multiferroic cantilever structures are released by isotropic etching of silicon using SF6 plasma. Bending and cracks are observed in the released cantilever structures due to the generation of residual stress in the multilayer thin film. Effect of residual stress on the PZT - BFO cantilever structure is also verified by simulation.

Improved electrocaloric effect in (100)-oriented Pb0.97La0.02(Zr0.57Sn0.38Ti0.05)O3 antiferroelectric thick film by interface engineering

In this work, 1.5-μm Pb0.97La0.02(Zr0.57Sn0.38Ti0.05)O3 antiferroelectric thick films with and without a ZrO2 thin layer were deposited on LaNiO3(100)/Si(100) substrates. The effects of ZrO2 thin layer on the microstructure, electrical properties, and especial electrocaloric effect of the antiferroelectric films were studied in detail. Although the films both with and without ZrO2 buffer layer displayed (100)-preferred orientation, possessed dense and uniform surface microstructure, the ZrO2-buffered films have an enlarged grain size by 27%, compared with the thick films without the buffer layer. Accordingly, the dielectric constant and saturate polarization of this antiferroelectric thick films was improved by the insertion of ZrO2 thin layer, and simultaneously its leakage current was slightly reduced. As a result, a great improvement in cooling character caused by ferroelectric–antiferroelectric phase switching, was realized in the ZrO2-buffered films.

Electrical properties of Pb(Zr0.52Ti0.48)O3–BiFeO3 multilayers on non-platinized silicon substrate

Abstract In this study, a Pb(Zr0.52Ti0.48)O3/BiFeO3 (PZT–BFO) multilayer film is deposited by the sol–gel technique on a silicon substrate. Prior to the multilayer deposition, a ZrO2 buffer layer is introduced. The multilayer thin film shows the polycrystalline phase-pure perovskite structures of BFO and PZT. Surface morphology study indicates that the grain size of the film varies from 20 to 30 nm. In the absence of the bottom electrode, the electrical properties of the film are studied in-plane by fabricating interdigitated terminals (IDTs) on top of the film. The inter-IDT line gap is kept large (10 μm) to avoid shorting due to unintentional particle contamination. The remnant polarization of the film is found to be ∼35 μC/cm2 at a 100-V bias. The dielectric constant of the film is found to be 650 at 1 kHz. The film also showed a low leakage current density of ∼4 × 10−9 A/cm2 at 200 kV/cm.

Double nitridation of crystalline ZrO2/Al2O3 buffer gate stack with high capacitance, low leakage and improved thermal stability

The gate dielectric stack composed of crystalline ZrO2 and Al2O3 buffer layer treated with double nitridation was developed to reduce the capacitance equivalent thickness (CET), leakage current density (Jg), interfacial state density (Dit), and enhance thermal stability as well. A high dielectric constant of the gate stack was provided by the crystalline ZrO2 with tetragonal/cubic phase. The Jg and Dit were suppressed by the insertion of the Al2O3 buffer layer treated with remote NH3 plasma nitridation because of the deactivation of the oxygen vacancies and the well passivation of the Si dangling bonds. A further nitridation using remote N2 plasma on ZrO2 was carried out to reduce the CET and Jg by the enhancement of the dielectric constant and the deactivation of the grain boundaries and oxygen vacancies. Accordingly, a low CET of 1.09nm, Jg of 3.43×10−5A/cm2, and Dit of 3.35×1011cm−2eV−1 were achieved in the crystalline ZrO2/Al2O3 buffer gate stack treated with the double nitridation. The hysteresis was also minimized significantly by the post-deposition annealing at 800°C, which is attributed to the enhanced thermal stability. The results indicate that the crystalline high-K dielectrics/buffer layer with double nitridation treatments is a promising gate stack structure beneficial to the sub-nanometer CET scaling in the future.

X-ray photoelectron spectra and composition of YBa2Cu3O7 − δ films prepared by laser ablation

The Y3d, Ba3d 5/2, Cu2p 3/2, and O1s X-ray photoelectron spectra of thick (600 nm) superconducting YBa2Cu3O7 − δ films deposited on textured Ni-W substrates with Y2O3 + ZrO2 and CeO2 buffer layers have been studied. It has been established that, after the mechanical removal of surface layers with a diamond scraper (and as the analyzed region of the film approaches the interface), a decrease in the oxygen content leads to a decrease of the orthophase fraction and an increase of the tetraphase and Cu+ ion fractions. This is caused by the presence of elastic stresses in the superconducting film due to the lattice misfit between the phases making up a composite sample. These stresses prevent oxygen diffusion involved in oxidizing annealing. The spectra of the superconducting film have not revealed signals generated by elements of the substrate and buffer layers.

Ni-based anode-supported Al2O3-doped-Y2O3-stabilized ZrO2 thin electrolyte solid oxide fuel cells with Y2O3-stabilized ZrO2 buffer layer

In order to reduce the sintering temperature of Ni-based anode-supported thin 8 mol% yttria-stabilized zirconia (YSZ) elsectrolyte solid oxide fuel cells (SOFCs), alumina, with a weight percent of 1, 3, 5, and 7, is respectively doped into YSZ as sintering aid. A pure YSZ buffer layer is introduced between the Al2O3-doped-YSZ electrolyte and Ni–YSZ anode, to prevent Al2O3 and NiO from forming non-conductive spinel NiAl2O4. The experimental results show that doping proper amount of Al2O3 doping can reduce the sintering temperature of YSZ, e.g., 1 wt.% doping decreases the temperature from 1673 K to 1573 K. Anode-supported SOFCs are prepared with Al2O3-doped-YSZ electrolytes sintered at different temperatures. Electrochemical characterization of the SOFCs shows that the single cell with 1 wt.% alumina-doped YSZ electrolyte sintered at 1573 K gives the highest output. The effect of alumina doping on sintering behavior and electrical performance of YSZ is discussed in detail.

Electrolytic deposition of fluorine-doped hydroxyapatite/ZrO2 films on titanium for biomedical applications

A novel method of electrolytic fluorine-doped hydroxyapatite/ZrO2 double-layer coating was conducted on medical titanium in ZrO(NO3)2 aqueous solution and subsequently in the mixed solution of Ca(NO3)2, NH4H2PO4 and NaF. The microstructure, phase composition, bond strength, dissolution rate and corrosion resistance of the films were studied. Results revealed that the additions of F− reduced the crystallite and increased the crystallinity of hydroxyapatite, structure of apatite was changed from micro-petal-like crystals to nano-needle-like crystals, which aligned vertically to the substrate. The approximately 10μm thick layers was much denser and uniform. Addition of ZrO2 buffer layer could improve the bond strength between the fluorine-doped hydroxyapatite layer and the substrate. The bond strength of the double-layer coating was found to be significantly higher than that of pure hydroxyapatite coating even after soaking in normal saline for two weeks. In physiological solution, the double-layer coating showed lower dissolution rate and stronger corrosion resistance than pure hydroxyapatite coating.

Unipolar Resistive Switching Characteristics of a $ \hbox{ZrO}_{2}$ Memory Device With Oxygen Ion Conductor Buffer Layer

Oxygen ion migration is an important factor in the formation and rupture of a conducting filament to cause resistive switching (RS) behavior. A calcium oxide-doped zirconium oxide <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$( \hbox{CaO:ZrO}_{2})$</tex></formula> oxygen ion conductor buffer layer is introduced between the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{Ti/ZrO}_{2}$</tex></formula> interface of conventional <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{Ti/ZrO}_{2}/\hbox{Pt}$</tex></formula> memory devices to improve their unipolar RS properties. Increasing the CaO doping concentration to 2 mol% introduces higher oxygen vacancy content within the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{CaO:ZrO}_{2}$</tex></formula> buffer layer, leading to higher oxygen ion conductivity. This allows more oxygen ions to migrate from the oxygen reservoir laterally and vertically across the 2-mol% <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{CaO:ZrO}_{2}$</tex></formula> buffer layer to the region where the conducting filament forms and ruptures. Therefore, the Ti/2-mol% <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$ \hbox{CaO:ZrO}_{2}/\hbox{ZrO}_{2}/\hbox{Pt}$</tex></formula> device in this letter exhibits good endurance, high-speed switching (50 ns) without soft errors, stubborn nondestructive readout, and stable retention at 150 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}\hbox{C}$</tex></formula> .

Fabrication of the Cobalt Ferrite/Modified Sodium Bismuth Titanate 0-3 Multiferroic Composites via Diffusion-blocking

通过溶胶-凝胶工艺在CoFe 2 O 4 (简称CFO)粉体表面包覆二氧化锆陶瓷层来阻挡烧结过程中铁磁相与铁电相之间的离子扩散. 包覆后的CFO与0.92(Bi 0.5 Na 0.5 )TiO3-0.02(Bi 0.5 K 0.5 )TO 3 -0.06BaTiO 3 (简称BNBT) 陶瓷粉体分别按照 x CFO/(1- x ) BNKLABT (质量分数 x = 0.05、0.10、0.15、0.20、0.25、0.30)混合均匀, 并用聚乙烯醇为粘结剂模压成圆片; 再经过1050℃烧结制备了铁磁/铁电0-3型复合材料. XRD分析表明: 二氧化锆在高温烧结过程中对离子扩散具有良好的阻挡作用. 复合陶瓷的耐击穿电压大于75kV/cm. 测量结果表明: 复合陶瓷的压电应变常数、机电耦合系数、介电常数和剩余极化随CFO含量的增加而降低; 磁电耦合系数、介电损耗随CFO含量的增加而有所增大. -35mm×1.5mm的复合陶瓷样品( x =0.05)在谐振频率(90kHz)和199kA/m 偏置磁场下的磁电系数为1.39V/A.

Characteristics of Strontium Bismuth Tantalate Film with ZrO2 Buffer Layer for Non-Volatile Memory Applications

We have investigated the interfacial and electrical properties of metal-ferroelectric-insulator-semiconductor capacitors with SrBi2Ta2O9 ferroelectric films grown on ZrO2 buffer layer coated Si. Interfacial and surface roughness parameters of heterostructures were extracted from the simulation of specular x-ray reflectivity data. For as-deposited film, no interfacial layer is found between SBT and ZrO2 from simulation data, however, an accurate fit can only be possible if a thin SiO2 layer is assumed at ZrO2/Si interface. On annealing, the formation of an inhomogeneous interfacial layer between SBT/ZrO2 interfaces having thickness 1.3 nm is observed.

Influence of O2 Pressure on the Structure and Surface Morphology of YSZ Layer for YBCO Coated Conductor Deposited by PLD on Ni-W Tape

Yttria-stabilized ZrO2 (YSZ) buffer layers were prepared on Ni-5%W tapes coated with CeO2-seed layers by a pulsed laser deposition (PLD) technique. The influences of oxygen pressure on the structure and surface morphology of YSZ buffer layers for YBCO coated conductors was investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Atomic Force Microscope (AFM) were used to characterize YSZ films. It was found that the structure and surface morphology were sensitive to the oxygen pressure. When the O2 pressure was higher than 1 mTorr, the YSZ film had mixed orientation and rugged surface. When the oxygen pressure was reduced to 0.5 mTorr, YSZ film had the pure (001) orientation. The surface became smooth as the oxygen pressure decreased. However, when the pressure was low to 0.1 mTorr, X-ray diffraction peaks form YSZ (002) were weak and the rough surface appeared again. The results could be explained either by plume stoichiometric changes, gas and ions interaction, or atomic rearrangement on the substrate.

Fabrication and Characterization of Pb(Zr0.53,Ti0.47)O3-Pb(Nb1/3,Zn2/3)O3 Thin Films on Cantilever Stacks

0.9Pb(Zr0.53,Ti0.47)O3-0.1Pb(Zn1/3,Nb2/3)O3 (PZT–PZN) thin films and integrated cantilevers have been fabricated. The PZT–PZN films were deposited on SiO2/Si or SiO2/Si3N4/SiO2/poly-Si/Si membranes capped with a sol–gel-derived ZrO2 buffer layer. It is found that the membrane layer stack, lead content, existence of a template layer of PbTiO3 (PT), and ramp rate during film crystallization are critical for obtaining large-grained, single-phase PZT–PZN films on the ZrO2 surface. By controlling these parameters, the electrical properties of the PZT–PZN films, their microstructure, and phase purity were significantly improved. PZT–PZN films with a dielectric constant of 700 to 920 were obtained, depending on the underlying stack structure.

Influence of MgO and ZrO2 buffer layers on dielectric properties of Ba(Zr0.20Ti0.80)O3 thin films prepared by sol–gel processing

Ba(Zr0.20Ti0.80)O3 (BZT) thin films are deposited on Pt(111)/Ti/SiO2/Si, MgO and ZrO2 buffered Pt(111)/Ti/SiO2/Si substrates by a sol–gel process. The BZT thin films directly grown on Pt(111)/Ti/SiO2/Si substrates exhibit highly (111) preferred orientation, while the films deposited on Pt(111)/Ti/SiO2/Si substrates with MgO and ZrO2 buffer layers show highly (110) preferred orientation. At 100kHz, dielectric constants are 417, 311 and 321 for the BZT thin films grown on Pt(111)/Ti/SiO2/Si, MgO and ZrO2 buffered Pt(111)/Ti/SiO2/Si substrates, respectively. The difference in dielectric properties of three BZT films can be attributed to the series capacitance effect, interface conditions and their orientations.

Electrical properties of metal-ferroelectric-insulator-semiconductor field effect transistors (MFIS-FETs) using the polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE))/ZrO2/Si structure

In this study, we fabricated the n-channel metal-ferroelectric-insulator-semiconductor field effect transistors (MFIS-FETs) using an Au/polyvinylidene fluoride-trifluoroethylene P(VDF-TrFE)/ZrO2/Si(100) structures. The ZrO2 thin film had the equivalent oxide thickness (EOT) value of around 9 nm. And the P(VDF-TrFE) film on a ZrO2/Si structure showed good ferroelectric property with memory window width of 2.5 V for a bias voltage sweeping of ±7 V. The leakage current density of this MFIS structure showed very excellent insulation property with about 9 × 10−8 A/cm2 at 5 V. Based on these results, we fabricated and investigated MFIS-FETs with ferroelectric polymer P(VDF-TrFE) film and ZrO2 buffer layer. The memory window width and on/off ratio of the MFIS-FET was about 4.5 V and 103, respectively. These results predicted that the P(VDF-TrFE) thin film would be useful for the realization of 1-transistor type ferroelectric memory.

Growth of Chemical Solution Deposited $^{\rm TFA}{\rm YBCO}/^{\rm MOD}({\rm Ce},{\rm Zr}){\rm O}_{2}/^{\rm ABAD}{\rm YSZ/SS}$Coated Conductors

All chemical solution deposited coated conductors on <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ABAD</sup> YSZ/SS tapes with critical current densities at 77 K of J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> = 1.8 MA / cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> have been obtained. Superconducting YBCO films were grown by the trifluoroacetates route on top of metal organic deposited (Ce, Zr) O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> buffer layers. Planarity of the CZO layer is the key for the high quality growth of the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TFA</sup> YBCO films reaching J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> (77 K, sf) = 5.2 MA / cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Granularity effects dominate J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> (H) at low fields while, at 77 K, for fields above 2 T, J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> of the coated conductor exhibits the same value as those obtained on single crystals.

Interfacial and electrical properties of SrBi2Ta2O9/ZrO2/Si heterostructures for ferroelectric memory devices

We have investigated the interfacial and frequency dependent electrical properties of metal-ferroelectric-insulator-semiconductor capacitors with SrBi2Ta2O9 (SBT) ferroelectric films grown on ZrO2 buffer layer coated Si. Heterostructure SBT and ZrO2 thin films were deposited using rf magnetron sputtering. Interfacial and surface roughness parameters of heterostructures were extracted from the simulation of specular x-ray reflectivity data. The structure exhibited clockwise capacitance-voltage hysteresis with a maximum memory window of 2.0 V at a bias voltage of ±7 V. Frequency dependent (5 kHz–1 MHz) measurements at room temperature indicated that the clockwise hysteresis originates from the ferroelectric domain reversal. A minimum leakage current density of 4×10−8 A/cm2 of fabricated capacitors at an applied voltage of ±5 V revealed that the ZrO2 buffer layer prevents the interfacial diffusion between SBT thin film and the substrate, resulting in an improvement of interface quality. The charge retention time of the ferroelectric capacitor was studied as a function of buffer layer thickness.

Preparation of PLZT Antiferroelectric Thin Films on ZrO2 Buffered Substrates

Pb0.97La0.02Zr0.95Ti0.05O3 (PLZT) antiferroelectric thin films were deposited on ZrO2 buffered Pt (111)/Ti/SiO2/Si (100) through sol-gel process. XRD results indicated that films derived on ZrO2 buffered Pt (111)/Ti/SiO2/Si (100) substrates showed random microcrystal structure. The antiferroelectric nature of the films was confirmed by P-E at room temperature. The C-V behaviors of the PLZT films with and without ZrO2 buffer layer were studied respectively, as a function of temperature. The temperature dependence of the dielectric constant displayed the similar behavior in both cases, but the PLZT films with a buffer layer had smaller dielectric constant.

Electrical Properties of Lead Zirconate Titanate Thin Films With a ZrO2 Buffer Layer on an Electroless Ni‐Coated Cu Foil

The effect of zirconia (ZrO2) buffer layers on the phase development and electrical properties of lead zirconate titanate (PZT, 52/48) capacitors on an electroless Ni (P)‐coated Cu foil was investigated. It was demonstrated that the buffer layer can be used to engineer the final properties. The incorporation of the ZrO2 buffer layers retained acceptable capacitance densities (&gt;350 nF/cm2 for 50 nm thick ZrO2), while significantly reducing leakage currents and improving reliability (&lt;10−7 A/cm2 after 1 h at 25 VDC for 100 nm thick ZrO2), compared with PZT thin films directly on electroless Ni (P). The results are particularly important for embedded capacitor applications.