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Microstructural characterization of nanostructured Al2O3-ZrO2 eutectic layer by laser rapid solidification method
摘要： In the present work, nanostructured surface layers of Al2O3-ZrO2 eutectic with a thickness of approximate 1000 μm and free of cracks and pores were produced on the surface of conventionally-sintered Al2O3-ZrO2 ceramic via the laser irradiation rapid solidification process. The molten pool geometry and microstructure were characterized by scanning electron microscopy and Raman spectroscopy. The geometrical evolution of molten pool in response to laser power and laser scanning velocity was established, where the top view of molten pool exhibits a circular shape at low velocities and gradually evolves into an oval-shaped surface at high velocities. Singular Al2O3-ZrO2 eutectic colonies with a size of 100-200 μm, which is formed around a spontaneously nucleated dendritic ZrO2 core, are found on the surface of laser-remelted layer. The eutectic colony has an interphase spacing of 190-280 nm. The variation of eutectic spacing with growth rate is essentially linear on the logarithmic scale as λ=KV-0.4 by binary regression analysis. Predicted by the Jackson-Hunt theory on eutectic solidification (JH theory), the eutectic spacing is consistent with the inverse-square-root dependence on growth rate with a proportionality constant of 3.32. The eutectic colonies consist of α-Al2O3, t-ZrO2 and m-ZrO2 phases, where α-Al2O3 and t-ZrO2 are the dominant phases and the m-ZrO2 phase increases with the decrease of laser scanning velocity.
关键词： Al2O3-ZrO2,Nanoeutectic layer,Laser remelting,Surface nanostructuring
更新于2025-11-28 14:24:20
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Fluorescence spectra of colloidal self-assembled CdSe nano-wire on substrate of porous Al <sub/>2</sub> O <sub/>3</sub> /Au nanoparticles
摘要： We present a self-assembly method to prepare array nano-wires of colloidal CdSe quantum dots on a substrate of porous Al2O3 film modified by gold nanoparticles. The photoluminescence (PL) spectra of nanowires are in situ measured by using a scanning near-field optical microscopy (SNOM) probe tip with 100-nm aperture on the scanning near-field optical microscope. The results show that the binding sites from the edge of porous Al2O3 nanopores are combined with the carboxyl of CdSe quantum dots’ surface to form an array of CdSe nanowires in the process of losing background solvent because of the gold nanoparticles filling the nano-holes of porous Al2O3 film. Compared with the area of non-self-assembled nano-wire, the fluorescence on the Al2O3/Au/CdSe interface is significantly enhanced in the self-assembly nano-wire regions due to the electron transfer conductor effect of the gold nanoparticles’ surface. In addition, its full width at half maximum (FWHM) is also obviously widened. The method of enhancing fluorescence and energy transfer can widely be applied to photodetector, photocatalysis, optical display, optical sensing, and biomedical imaging, and so on.
关键词： porous Al2O3 film,colloidal self-assembled method,CdSe nano-wire,enhanced photoluminescence
更新于2025-11-25 10:30:42
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Effects of TiO <sub/>2</sub> doping on microstructure and properties of directed laser deposition alumina/aluminum titanate composites
摘要： Al2O3-based composite ceramics have excellent high temperature performance and are ideal materials for preparing hot end components. However, poor fracture toughness and thermal shock resistance limit its applications. Based on the excellent low thermal expansion characteristics and thermal shock resistance of Al2TiO5 ceramic, different composition ratios of Al2O3/Al2TiO5 composite ceramics were prepared by directed laser deposition (DLD) technology. Effects of TiO2 doping amount on microstructure and properties of the composite ceramics were investigated. Results show that α-Al2O3 phase is discretely distributed in the continuous aluminum titanate matrix when TiO2 doping amount between 2 and 30 mol%. With the increase of TiO2 doping amount, content of Al2O3 gradually decreases and its morphology changes from cellular to dendritic. When TiO2 doping amount reaches 43.9 mol%, the microstructure transforms into fine Al2TiO5/Al6Ti2O13 eutectic structure. Property test results show that Al2O3/Al2TiO5 composite ceramics have good comprehensive mechanical properties when TiO2 doping amount between 2 and 6 mol%.
关键词： Al2O3/Al2TiO5,microstructure,Additive manufacturing,properties,composite ceramics
更新于2025-11-21 11:03:13
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Effect of HCl Cleaning on InSb-Al<sub>2</sub>O<sub>3</sub> MOS Capacitors
摘要： In this work, the role of HCl treatments on InSb surfaces and InSb-Al2O3 dielectric interfaces is characterised. X-ray photoelectron spectroscopy (XPS) measurements indicate that HCl diluted in and rinsed with isopropanol (IPA) results in a surface layer of InCl3 which is not present for similar HCl-water processes. Furthermore, this InCl3 layer desorbs from the surface between 200°C and 250°C. Metal-oxide-semiconductor capacitors (MOSCAPs) were fabricated using atomic layer deposition (ALD) of Al2O3 at 200°C and 250°C and the presence of InCl3 was associated with a +0.79 V flatband voltage shift. The desorption of the InCl3 layer at 250°C reversed this shift but the increased process temperature resulted in increased interface-trapped charge (Dit) and hysteresis voltage (VH). This shift in flatband voltage, which does not affect other figures of merit, offers a promising route to manipulate the threshold voltage of MOS transistors, allowing enhancement-mode and depletion-mode devices to be fabricated in parallel.
关键词： surface cleaning,III-V,ALD,Al2O3,InSb,dielectric interface,MOSCAP,HCl
更新于2025-11-14 17:28:48
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Electrical characterization of high k-dielectrics for 4H-SiC MIS devices
摘要： We report promising results regarding the possible use of AlN or Al2O3 as a gate dielectric in 4H-SiC MISFETs. The crystalline AlN ?lms are grown by hot wall metal organic chemical vapor deposition (MOCVD) at 1100 °C. The amorphous Al2O3 ?lms are grown by repeated deposition and subsequent low temperature (200 °C) oxidation of thin Al layers using a hot plate. Our investigation shows a very low density of interface traps at the AlN/4H-SiC and the Al2O3/4H-SiC interface estimated from capacitance-voltage (CV) analysis of MIS capacitors. Current-voltage (IV) analysis shows that the breakdown electric ?eld across the AlN or Al2O3 is ～ 3 MV/cm or ～ 5 MV/cm respectively. By depositing an additional SiO2 layer by plasma enhanced chemical vapor deposition at 300 °C on top of the AlN or Al2O3 layers, it is possible to increase the breakdown voltage of the MIS capacitors signi?cantly without having pronounced impact on the quality of the AlN/SiC or Al2O3/SiC interfaces.
关键词： MIS structure,Interface traps,Al2O3/4H-SiC interface,AlN/4H-SiC interface
更新于2025-11-14 17:28:48
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Highly Flexible and Transparent Memristive Devices using Cross-Stacked Oxide/Metal/Oxide Electrode Layers
摘要： Flexible and transparent memristive devices (FT-memristors) are considered to be among promising candidates for future nonvolatile memories. To realize these devices, it is essential to achieve flexible and transparent conductive electrodes (TCEs). However, conventionally-used TCEs such as indium tin oxide, gallium zinc oxide, and indium zinc oxide are not so flexible and even necessitate thermal annealing for high conductivity and optical transmittance. Here, we introduce Ag/ZnO/Ag and Ag/Al2O3/Ag-based FT memristors using cross-stacked oxide/metal/oxide electrode layers (i.e., ZnO/Ag/ZnO + ZnO/Ag/ZnO and Al2O3/Ag/Al2O3 + Al2O3/Ag/Al2O3) without using any annealing process on polyethylene terephthalate substrates (PETs). Both Ag/ZnO/Ag- and Ag/Al2O3/Ag-based FT-memristors on PETs exhibited excellent properties, including high transmittance (> 86% in the visible region), high ON/OFF current ratios (> 103), and long retention times (> 105 s). In addition, they showed very stable and flexible characteristics on PETs even after 2500 bending cycles with a bending radius of 8.1 mm. Finally, we analyzed transmission electron microscopy images and time-of-flight secondary ion mass spectroscopy profiles to identify switching mechanisms in these devices.
关键词： Al2O3/Ag/Al2O3,filament,memristive device,Transparent and flexible electrode,ZnO/Ag/ZnO
更新于2025-09-23 15:23:52
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Chemical Analysis of the Interface between Hybrid Organic-Inorganic Perovskite and Atomic Layer Deposited Al2O3
摘要： Ultrathin metal oxides prepared by atomic layer deposition (ALD) have gained utmost attention as moisture and thermal stress barrier layers in perovskite solar cells (PSCs). We have recently shown that 10 cycles of ALD Al2O3 deposited directly on top of the CH3NH3PbI3-xClx perovskite material, are effective in delivering a superior PSC performance with 18% efficiency (compared to 15% of the Al2O3-free cell) with a long-term humidity-stability of more than 60 days. Motivated by these results, the present contribution focuses on the chemical modification which the CH3NH3PbI3-xClx perovskite undergoes upon growth of ALD Al2O3. Specifically, we combine in situ Infrared (IR) spectroscopy studies during film growth, together with X-ray Photoelectron Spectroscopy (XPS) analysis of the ALD Al2O3/perovskite interface. The IR-active signature of the NH3+ stretching mode of the perovskite undergoes minimal changes upon exposure to ALD cycles, suggesting no diffusion of ALD precursor and co-reactant (Al(CH3)3 and H2O) into the bulk of the perovskite. However, by analyzing the difference between the IR spectra associated with the Al2O3 coated perovskite and the pristine perovskite, respectively, changes occurring at the surface of perovskite are monitored. The abstraction of either NH3 or CH3NH2 from the perovskite surface is observed as deduced by the development of negative N-H bands associated to its stretching and bending modes. The IR investigations are corroborated by XPS study, confirming the abstraction of CH3NH2 from the perovskite surface, whereas no oxidation of its inorganic framework is observed within the ALD window process investigated in this work. In parallel, the growth of ALD Al2O3 on perovskite is witnessed by the appearance of characteristic IR-active Al-O-Al phonon and (OH)-Al=O stretching modes. Based on the IR and XPS investigations, a plausible growth mechanism of ALD Al2O3 on top of perovskite is presented.
关键词： infrared spectroscopy,x-ray photoelectron spectroscopy,atomic layer deposition,Al2O3,perovskite
更新于2025-09-23 15:23:52
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Impact of oxide/barrier charge on threshold voltage instabilities in AlGaN/GaN metal-oxide-semiconductor heterostructures
摘要： Threshold voltage instabilities in AlGaN/GaN metal-oxide-semiconductor (MOS) heterostructures were investigated by means of capacitance-voltage (CV) hysteresis measurement and simulations. We focused on the impact of net charge at oxide/semiconductor interface (Qint) on the CV hysteresis. Our simulations suggest that due to different band bending at the interface, any positive or negative Qint with lower density (in the order of 1012 cm?2) results in a presence of relatively shallow unoccupied oxide/barrier interface states in equilibrium. On the other hand, high density of negative Qint (Qint/q ≈ ?1013 cm?2) results in very deep unoccupied interface states, which in turn leads to incomplete electron re-emission during backward CV sweep and thus increased CV hysteresis of the MOS heterostructures compared to previous case. Impact of Qint is illustrated experimentally on MOS heterostructures with Al2O3 gate dielectric grown by metal-organic chemical vapor deposition, showing Qint of ?1.2 × 1013 and +0.5 × 1012 cm?2 for structures with and without post-deposition annealing, respectively. Our results therefore suggest that normally-off AlGaN/GaN MOS heterostructure field-effect transistors featuring high density of negative Qint can be expected to be more susceptible for threshold voltage instabilities compared to normally-on counterparts.
关键词： MOS,Al2O3 gate dielectric,Heterostructure field-effect transistor,Interface traps,AlGaN/GaN
更新于2025-09-23 15:23:52
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Photoluminescence, scintillation and TSL properties of Eu-doped Al2O3 transparent ceramics synthesized by spark plasma sintering method
摘要： We synthesized Al2O3 transparent ceramics doped with different concentrations of Eu (0.001, 0.01, 0.1 and 1.0%) by the spark plasma sintering (SPS) method, and then we investigated their photoluminescence (PL), scintillation and thermally-stimulated luminescence (TSL) properties. In the PL, the samples showed a broad emission peak at 400 nm due to the 5d-4f transitions of Eu2+ and several sharp emission peaks across 550–750 nm due to the 4f-4f transitions of Eu3+ and the 3d-3d transitions of Cr3+ impurity ion. In addition to these peaks over 550–750 nm, in scintillation, the samples exhibited two broad peaks over 300–400 nm possibly due to not the 5d-4f transitions of Eu2+ but F and F+ centers. In TSL, the glow curve consisted of peaks at approximately 100, 160, 210 and 320 °C. The TSL intensity of the 0.001% Eu-doped sample was the highest, and the TSL response was confirmed to be linear to irradiated X-ray dose in the range from 0.1 to 1000 mGy.
关键词： Transparent ceramic,Scintillator,Eu,Dosimeter,Al2O3
更新于2025-09-23 15:23:52
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[IEEE 2018 14th International Conference on Advanced Trends in Radioelecrtronics, Telecommunications and Computer Engineering (TCSET) - Lviv-Slavske, Ukraine (2018.2.20-2018.2.24)] 2018 14th International Conference on Advanced Trends in Radioelecrtronics, Telecommunications and Computer Engineering (TCSET) - Nanoengineering of anisotropic materials for creating the active optical cells with increased energy efficiency
摘要： In this paper the state-of-the-art for exploiting the unique physical and chemical properties of crystalline nanomaterials and their possible applications for creating optical cells with increased energy efficiency are discussed. Using a method of growing crystals from a solution the KDP and TGS nanocrystals were grown in the mesopores of the Al2O3 matrix where the direction of growth was discussed. To investigate the developed nanocomposites the X-ray analysis was used and it showed the predominant crystal orientation of the KDP and TGS in the direction [001] which coincides with the direction of the cylindrical pores. Thus, the possibility of growing of the KDP and TGS nanocrystals in the mesopores of the Al2O3 matrix was developed and provides the prospect of creating optical cells with increased energy efficiency.
关键词： X-ray analysis,anisotropic materials,crystalline nanocomposites,nanoporous matrices,Al2O3,nanofiller KDP and TGS
更新于2025-09-23 15:23:52