ZrO2 Interface Research Articles

MeV Au ion irradiation in silicon and nanocrystalline zirconia film deposited on silicon substrate

Nanocrystalline zirconia (ZrO2) film with thickness of 305nm deposited on a silicon substrate was irradiated with 2MeV Au ions to different fluences at different temperatures. The implanted ion profiles were measured by time-of-flight secondary ion mass spectrometry (ToF-SIMS) and simulated using the stopping and range of ions in matter (SRIM) code, respectively. The experimental results show that a large fraction of the incident Au ions penetrates through the ZrO2 film and are deposited into the Si substrate. At the interface of ZrO2 and Si, a sudden decrease of Au concentration is observed due to the much larger scattering cross section of Au in ZrO2 than in Si. The depth profile of the Au ions is measured in both the ZrO2 films and the Si substrates, and the results show that the Au distribution profiles do not exhibit a dependence on irradiation temperature. The local Au concentration increases proportionally with the irradiation fluence, suggesting that no thermal or irradiation-induced redistribution of the implanted Au ions. However, the Au concentration in the ZrO2 films, as determined by SIMS, is considerably lower than that predicted by the SRIM results, and the penetration depth from the SIMS measurements is much deeper than that from the SRIM predictions. These observations can be explained by an overestimation of the electronic stopping power, used in the SRIM program, for heavy incident ions in light targets. Overestimation of the heavy-ion electronic stopping power may lead to errors in local dose calculation and underestimation of the projected range of slow heavy ions in targets that contain light elements. A quick estimate based on a reduced target density may be used to compensate the overestimation of the electronic stopping power in the SRIM program to provide better ion profile prediction.

Preparation and characterization of tetragonal dominant nanocrystalline ZrO2 obtained via direct precipitation

Nanocrystalline ZrO2 has been prepared by using ZrO(NO3)2·6H2O through direct precipitation followed by calcination. Transmission Electron Microscopic characterization of the powder shows the particle size dominantly of the order of 10nm. The X-ray diffraction pattern shows the formation of both tetragonal and monoclinic phases where the tetragonal phase is dominant. The estimation of tetragonal phase has been carried out using the Raman scattering spectroscopy. Zeta potential of suspended ZrO2 in aqueous medium with surfactant has been measured at varying pH and temperature to understand the effects of temperature at the interface of nanocrystalline ZrO2 in water.

Fabrication of SiO<SUB>2</SUB>@ZrO<SUB>2</SUB>@Y<SUB>2</SUB>O<SUB>3</SUB>:Eu<SUP>3+</SUP> Core-Multi-Shell Structured Phosphor

ZrO2 interface was designed to block the reaction between SiO2 and Y2O3 in SiO2@Y2O3:Eu coreshell structure phosphor. SiO2@ZrO2@Y2O3:Eu core-multi-shell phosphors were successfully synthesized by combing an LBL method with a Sol-gel process. Based on electron microscopy, X-ray diffraction, and spectroscopy experiments, compelling evidence for the formation of the Y2O3:Eu outer shell on ZrO2 were presented. The presence of ZrO2 layer on SiO2 core can block the reaction of SiO2 core and Y2O3 shell effectively. By this kind of structure, the reaction temperature of the SiO2 core and Y2O3 shell in the SiO2@Y2O3:Eu core-shell structure phosphor can be increased about 200-300 degrees C and the luminescent intensity of this structure phosphor can be improved obviously. Under the excitation of ultraviolet (254 nm), the Eu3+ ion mainly shows its characteristic red (611 nm, 5D0-7F2) emissions in the core-multi-shell particles from Y2O3:Eu3+ shells. The emission intensity of Eu3+ ions can be tuned by the annealing temperatures, the number of coating times, and the thickness of ZrO2 interface, respectively.

Preparation and Characterization of Conductive Polyaniline/Zirconia Nanoparticles Composites

Conductive polyaniline/zirconia (PANI/ZrO2) composites have been synthesized by in-situ polymerization of aniline in the presence of ZrO2 nanoparticles. The structure and morph- ology of composites were characterized by Fourier-transform infrared spectra (FTIR), thermo- gravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscope (SEM). The conductivity was also investigated. The results showed that PANI and ZrO2 nanoparticles were not simply blended, and a strong interaction existed at the interface of ZrO2 and PANI. It was probably a composite at molecular level. The composites were more thermal stability than that of the pure PANI. XRD analyses confirmed PANI deposited on the surface of ZrO2 nanoparticles had no effect on crystallization performance of ZrO2 nanoparticles. Electrical conductivity measurements indicated that the conductivity of PANI/ZrO2 composites was much higher than that of PANI and the maximum conductivity obtained was 11.27S/cm at 15 wt% of ZrO2 nanoparticles.

Bit-Error-Rate Evaluation of Super-Resolution Near-Field Structure Read-Only Memory Discs with Semiconductive Material InSb

Bit-error-rate (bER) evaluation using hardware (H/W) evaluation system is described for super-resolution near-field structure (super-RENS) read-only-memory (ROM) discs fabricated with a semiconductor material, In–Sb, as the super-resolution active layer. bER on the order of 10-5 below a criterion of 3.0×10-4 is obtained with the super-RENS ROM discs having random pattern data including a minimum pit length of 80 nm in partial response maximum likelihood of the (1,2,2,1) type. The disc tilt, focus offset, and read power offset margins based on bER of readout signals are measured for the super-RENS ROM discs and are almost acceptable for practical use. Significant improvement of read stability up to 40,000 cycles realized by introducing the ZrO2 interface layer is confirmed using the H/W evaluation system.

Atomic and electronic structures at ZnO and ZrO2 interface for transparent thin‐film transistors

AbstractIn this paper, we report the studies of atomic and electronic structures at ZnO and ZrO2 interface. The epitaxial heterostructures were grown by laser molecular beam epitaxy and the interface atomic structure was determined by using high‐resolution transmission electron microscopy (TEM). Band alignment for high‐k ZrO2 layer on ZnO was investigated by in situ X‐ray photoemission spectroscopy (XPS) characterization and first‐principles calculations based on density functional theory (DFT). The valence and conduction band offsets (CBOs) were found to be 0.27 ± 0.05 eV and 2.16 ± 0.05 eV, respectively. The results are in good agreement with values from theoretical calculations. The large CBO and small lattice mismatch between ZnO and ZrO2 suggest potential for ZrO2 to be used as a gate dielectric in ZnO‐based transparent electronic devices.

Thermal Stability of Reliable Polycrystalline Zirconium Oxide for Nonvolatile Memory Application

Thermal stability of resistive switching of stoichiometric zirconium oxide thin films is investigated for high yielding nonvolatile memory application. The Al/ZrO2/Al cell fabricated in the conventional device process shows highly reliable switching behaviour between two distinct stable resistance states. The retention capabilities are also tested under various conditions and temperatures. The excellent performance of Al/ZrO2/Al cell can be explained by assuming that anode/ ZrO2 interface exists and by conducting filament forming/rupture mechanism. The device failure is illustrated in terms of permanent conducting filaments formation.

The positive bias temperature instability of n-channel metal-oxide-semiconductor field-effect transistors with ZrO2 gate dielectric

The positive bias temperature instability of n-channel metal-oxide-semiconductor field-effect transistors with ZrO2 gate dielectric was studied. It was observed that the degradation in threshold voltage (ΔVT) has an exponential dependence on the stress time in the temperature range from 25to75°C. The measurement of subthreshold slope (ΔS) during stress indicates that the degradation in VT is due to the interface trap charges Qit. The extracted activation energy of 0.3–0.5eV is related to a degradation dominated by the release of atomic hydrogen in the Si–ZrO2 interface.

ZrO2 and HfO2 Interface with Silicon: a DFT Study of Stress and Strain Effects

not Available.

Characterization of metal-ferroelectric (BiFeO3)-insulator (ZrO2)-silicon capacitors for nonvolatile memory applications

The electric properties of ferroelectric BiFeO3 (BFO) thin films with ZrO2 insulating buffer on Si substrates fabricated by chemical solution deposition were investigated. ZrO2 demonstrates excellent insulating properties on Si substrates. The metal-ferroelectric-insulator-semiconductor (MFIS) structure exhibits clockwise capacitance-voltage hysteresis loops due to the ferroelectric polarization of BFO. The maximum memory windows are 0.66 and 0.78V, respectively, for BFO deposited on postannealed ZrO2 and on unannealed ZrO2 insulating layers. The small memory window of the BFO∕ZrO2 (postannealed) MFIS is caused by significant interface trap states on the BFO∕ZrO2 interface; this is supported by C-V measurements under varying frequency.

Solvation Dynamics at the Water/Zirconia Interface: Molecular Dynamics Simulations

We report the results of a molecular dynamics (MD) simulation study of solvation dynamics associated with electronic excitation of the coumarin 343 (C343) dye at the interface of water and zirconia (ZrO2). We use an all-atom representation of the species present in this system. The ZrO2 partial charges and C343 geometries and charge distributions in the ground and excited electronic states have been obtained from electronic structure calculations. Our work is inspired by recent time-resolved fluorescence experiments involving C343 adsorbed at the surface of zirconia nanoparticles dissolved in H2O and D2O (Pant, D.; Levinger, N. E. J. Phys. Chem. B 1999, 103, 7846). In addition to simulation of solvation dynamics, we investigate the structure and dynamics of the dye and water in the presence of a planar ZrO2 interface. We also address several issues relevant to the interpretation of experiments, including the solvent isotope effects and the ionization state of the carboxylate group of C343 on solvation dyn...

Influence of the Y2O3 Content and Temperature on the Mechanical Properties of Melt‐Grown Al2O3–ZrO2 Eutectics

The effect of Y2O3 content on the flexure strength of melt‐grown Al2O3–ZrO2 eutectics was studied in a temperature range of 25°–1427°C. The processing conditions were carefully controlled to obtain a constant microstructure independent of Y2O3 content. The rod microstructure was made up of alternating bands of fine and coarse dispersions of irregular ZrO2 platelets oriented along the growth axis and embedded in the continuous Al2O3 matrix. The highest flexure strength at ambient temperature was found in the material with 3 mol% Y2O3 in relation to ZrO2(Y2O3). Higher Y2O3 content did not substantially modify the mechanical response; however, materials with 0.5 mol% presented a significant degradation in the flexure strength because of the presence of large defects. They were nucleated at the Al2O3–ZrO2 interface during the martensitic transformation of ZrO2 on cooling and propagated into the Al2O3 matrix driven by the tensile residual stresses generated by the transformation. The material with 3 mol% Y2O3 retained 80% of the flexure strength at 1427°C, whereas the mechanical properties of the eutectic with 0.5 mol% Y2O3 dropped rapidly with temperature as a result of extensive microcracking.

Influence of Deposition Temperature on Mechanical Properties of Plasma-Sprayed Hydroxyapatite Coating on Titanium Alloy With ZrO<SUB>2</SUB> Intermediate Layer

Hydroxyapatite coatings were plasma sprayed on the Ti6A14V substrate with and without an intermediate ZrO2 layer; meanwhile the temperatures of substrates were varied at 90, 140, and 200 °C. The coatings were subjected to the standard adhesion test per ASTM C633-79. The purpose of the investigation was to study the effects of those processing variables on the bonding strength and failure behavior of the system. It is found that the bonding strengths of HA/ZrO2 and HA coatings generally decrease with increasing substrate temperature, except for the HA/ZrO2 coating deposited at 200 °C. The rationale of the results is attributed to the residual stress reported in the literature. Introducing ZrO2 bond coat is found to significantly promote the bonding strength of HA coating. The possible strengthening mechanism is the rougher surface of ZrO2 bond coat and the higher toughness of ZrO2, which provide the mechanical strengthening effects. The slightly denser HA in 200 °C deposited HA coating cannot explain the high bonding strength of the HA/ZrO2 coating, nor the mechanical strengthening effect of ZrO2 intermediate layer should apply. It is believed that a stronger diffusion bonding is formed at the interface of HA and ZrO2, which increases the bonding between them chemically. The bonding strengths of HA/ZrO2 and HA coatings are correlated with the area fraction of adhesive failure of the coatings. The correlation explains the findings in this study.

Thermal stability of polycrystalline silicon/metal oxide interfaces

The thermal stability of polycrystalline silicon (poly-Si)/ZrO2 interface was significantly enhanced when the poly-Si was plasma deposited using silane heavily diluted in He. With regard to this process, transmission electron microscopy shows a sharp poly-Si/ZrO2 interface that is stable at 1000 °C. When the poly-Si was deposited by chemical vapor deposition using undiluted silane gas, transmission electron microscopy shows strong reactions at the poly-Si/ZrO2 interface when annealed at 1000 °C. The increased stability can be attributed to He dilution, which may prevent hydrogen from reducing the metal oxide. Another explanation may be directly related to He-excited plasma, which is known to produce denser and more stable films.

Reaction steps of silicidation in ZrO2/SiO2/Si layered structure

Reaction steps of silicidation in ZrO2/SiO2/Si layered structure have been investigated in terms of ultrahigh vacuum annealing. Comparison of 2- and 20-nm ZrO2 films at 920 °C revealed that the trigger of silicidation is the contact of ZrO2, SiO, and Si accompanying disappearance of interfacial SiO2 layer due to SiO desorption. In the contact position, a small amount of SiO gas can easily change ZrO2 to ZrSi2. Moreover, this reaction model is also applicable to the silicidation of gate polycrystalline-Si (poly-Si)/ZrO2 interface.

Optimal low‐energy SIMS conditions for characterizing ZrO2/Si interfaces

AbstractDevelopment of high‐K gate dielectric materials has placed a stringent demand for inspection tools with ultrahigh depth resolving power and detection sensitivity. Low‐energy SIMS is potentially the technique of choice provided that the analytical related artifacts are well understood and efficiently suppressed. In this work we profiled superficial and buried metal–organic chemical vapour deposited ZrO2 films and investigated the artifacts involved in SIMS profiling at various beam conditions. It was demonstrated that O2+ beams at near‐normal incidence yielded extremely broad Zr down‐slopes in Si, an artifact likely due to a pronounced preferential sputtering of Si when the instantaneous surface reached the ZrO2/Si interfaces. Suppression of this artifact can be realized by probing O2+ beams at oblique incidence, favorably at 60° for a 1 keV O2+. Nevertheless, the normal‐incidence O2+ beam remained optimal for characterizing the up‐slope of Zr at the polycrystalline Si (polySi)/ZrO2 interface, owing to the minimized matrix effects and suppressed surface roughness. For profiling a gate stack (polySi/ZrO2/Si) at oblique incidences, the high depth resolution of low‐energy SIMS was hindered by the pronounced roughness in poly‐Si. This can be remedied by ion beam smoothing of the poly‐Si prior to SIMS profiling. Using the optimal SIMS conditions, we profiled poly‐Si/ZrO2/Si wafers with and without dopant activation anneal. The SIMS data revealed significant reactions between ZrO2 and Si upon thermal anneal at 1025°C for 10 s. Copyright © 2002 John Wiley & Sons, Ltd.

Laser-induced surface acoustic waves for evaluation of elastic stiffness of plasma sprayed materials

The elastic properties of plasma sprayed deposits have been evaluated using a laser-excited surface acoustic wave (SAW) technique and an inversion processing analysis. The SAWs including Lamb and Rayleigh waves were generated in plasma sprayed NiCoCrAlY and ZrO2, respectively, and their group velocity dispersions were used to determine the elastic properties (i.e.Young's modulus, Poison's ratio and density) of the deposits. Estimated elastic moduli from the velocity dispersions of A0-mode Lamb waves are in the range of 40–140 GPa for the deposits, which are much lower than the values 220–240 GPa of the comparable dense materials. The dramatic reductions in modulus and density of ZrO2 deposit have been attributed to the presence of high porosity and particularly microcracks. Moreover, this study has emphasized on exploiting the applicability of each kind of the SAWs for the elastic property evaluation of different sprayed materials. Both Lamb and Rayleigh wave dispersions are useful for the estimation of APS and VPS-deposited NiCrAlY, but S0-Lamb and Rayleigh waves are exceptional for that of sprayed ZrO2, because of its characterization of high acoustic attenuation and inconsequent displacement across the weak bonded interface of ZrO2 and substrate.

TEM Observation of the Zrc/Zro2 Interface Formed by Oxidation of Zrc Single Crystals

Microstructure at the interface of ZrC and ZrO2 formed by oxidation of a single crystal of ZrC with 100 faces at 600°C at an oxygen pressure of 2 kPa was observed by high-resolution transmission electron microscopy and scanning electron microscopy. The ZrO2 scale was shown to consist of two subscales, zones 1 and 2. The interfacial area in zone 1 was composed of regular lattice fringes corresponding to the 111, 200, and 220 lattices of cubic ZrO2 (c-ZrO2) crystallites 2 to 10 nm in size and an amorphous phase. The growth of crystallites occurred in zone 2, which visualized the interface of zones 1 and 2. Black thin films reminiscent of zone 1 were successfully separated, which were composed of amorphous carbon in which c-ZrO2 particles 2 to 20 nm in size were included.

ＺｒＯ２／ＮｉＣｒＡｌＹ溶射皮膜の繰返し熱衝撃破壊挙動

In order to make the test standard for thermal shock resistance of ceramic coatings, both fracture mechanisms of the coating and main factors for the fracture have to be clarified. In this study, cyclic thermal shock testings were carried out on the ZrO2/NiCrAlY plasma sprayed coatings, and unsteady thermal stress analyses by FEM were also conducted on these testings. The results obtained are summarized as follows.(1) ZrO2 coatings were suddenly spalled off completely during or just after the cooling process, after some cycles of thermal shock.(2) Fracture took place at the interface of ZrO2 sprayed particles about 10μm away from the ZrO2/NiCrAlY interface.(3) From the results of unsteady FEM analyses, large compressive stress was recognized in the ZrO2 coating during the cooling process.(4) From the results of both SEM observations and FEM analyses, it was revealed that the fracture of the coating was caused by unstable propagation of internal crack which was generated at the inside of the coating layer near the ZrO2/NiCrAIY interface.

Electron spin resonance investigation of ZrO2-supported ruthenium. Evidence of strong metal–support interaction

An e.s.r investigation of Ru/ZrO2 has shown that Ru centres are present in different oxidation states, two of which are paramagnetic: RuIII and RuI. The assignment of the electronic configuration follows from the results of the interaction of Ru/ZrO2 with CO, for the identification of RuIII and RuI, and with NO for the identification of RuII. Magnetic tensor components allow recognition of an RuIII–CO adduct (g∥= 2.039, g⊥= 2.003) and an RuI–CO adduct (g= 2.05) An RuII–NO species was also identified [g⊥= 2.00, g∥= 1.91,A⊥(N)=40 G]. The results of the interaction with O2 also have been discussed in order to give a fuller description of the electronic configuration of the surface ruthenium centres and of the interaction effects between metal and support centres. It appears that at the Ru–ZrO2 interface occurs an interaction stronger than in the Ru–γ-Al2O3 case, the strength depending also on the temperature of the pyrolysis used to obtain Ru/ZrO2 from the Ru3(CO)12/ZrO2 metal precursor. Also the analogous Rh/ZrO2 system was considered with respect to interaction with NO in order to compare the variation in the metal–support interaction owing to differences in the supported metal.