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Objectives: This research aimed to develop a guideline for evaluating safety and performance of electronic warm-acupuncture apparatus. With the development of medical devices like electronic warm-acupuncture apparatus with improved performance, convenience and safety measures compared to traditional warm-acupuncture needling, safety and performance guideline is a necessity.Methods: By referring to existing standards and guidelines of other electronic devices for Korean medicine with heating function, guideline for safety and performance assessment of electronic warm-acupuncture apparatus was draftedResults: The guideline, presents explanation for adequate temperature and settings of the apparatus, and safety measurements providing against thermal runaway situations along with guidelines for the manual. Guideline for detailed test method for the performance of the apparatus such as accuracy of temperature increase and the timer, and safety unit was also provided. The test items and suggested test methods for the requirements of biological, electrical and electromagnetic safety were referred to Korean approval documents of ministry of Food and Drug Safety.Conclusion: We proposed the relevant items to verify performance and safety of warm-acupuncture apparatus to assure patient safety and improve the quality of currently developing devices for application in clinical field.

A 42-year-old male patient with prolonged throat pain and discomfort, dry mouth, and general weakness and recently diagnosed with tonsillitis, pulmonary embolism, and venous thrombosis was admitted to the internal Korean medicine department. A sudden onset of diabetic ketoacidosis with hyperammonemia was diagnosed on the second day of treatment. During admission, the patient received insulin therapy, hydration, and traditional Korean medicine treatment, including herbal medicine. Subjective symptom change was evaluated daily and blood glucose level checked five times per day. At discharge, the patient’s fasting and postprandial blood sugar levels were adequate. After an additional two weeks of herbal treatment, the symptoms were significantly ameliorated. Thus, having been admitted with dysregulated glucose metabolism leading to a hyperglycemic crisis after a series of inflammatory events, the patient showed symptomatic improvements and decreased blood glucose after 18 days of hospitalization and treatment.

The thermodynamic stability limits of Sn(II) under ambient conditions imposes constraints on the densification of divalent tin based oxides. In the case of tin monoxide (SnO), a low temperature (≤ 300 °C) electric field assisted processing route (Cool-SPS) affords densification up to 90% of theoretical density. This is demonstrated for both conventional SnO and reactive tin(II) oxyhydroxide [Sn6O4(OH)4] precursor powders. The choice of starting precursor impacts both the optimized processing parameters and the resulting ceramic microstructure. Characterization of phase content and stability has been performed on both the precursor powders and resulting ceramics. Preliminary electrochemical property measurements are presented and their connection to observed microstructure and choice of initial precursor is discussed.

International audience; In this work, structural and dielectric properties of BaTi(1-x)ZrxO3 (BTZ) ceramics prepared by Spark Plasma Sintering (SPS) from powders obtained via Self-propagating High-temperature Synthesis (SHS) are shown to be strongly affected by the sintering temperature. In addition, a post-annealing treatment in air of the as-prepared ceramics leads to a transition from the hexagonal to the tetragonal and cubic phases. The SPS ceramics corresponding to compositions 0.05 ≤ x ≤ 0.20 and obtained at a sintering temperature of 1200 °C exhibit a standard ferroelectric behavior. In contrast, a diffuse phase transition is observed for the case of ceramics sintered at higher temperatures. Finally, the BTZ ceramic containing 5 at.% of Zr displays the best dielectric permittivity and piezoelectric properties as compared to the other compositions taken into account.

International audience; In this paper, a pyrolysis method is used to synthesize high quality VO2 powder. Black carbon and V2O5 powder are mixed and annealed at 650 °C or 800 °C under argon flow to initiate a carbo-reduction reaction. The 650 °C VO2 powder presents submicron particle size with an amorphous fraction estimated at 11.5%. With the increase of the annealing temperature up to 800 °C, grains become larger than the micron while the crystallinity goes up to 98.5% (i.e. amorphous fraction drops to 1.5%). This one-step process allows the preparation of quantities up to 10 g of VO2 powder and should be easily transferable to large-scale production. An innovative sintering process is then adopted to produce high quality thermochromic VO2 ceramics from the as-prepared VO2 powder. First, SPS process is used to obtain high-density VO2 pellet. Then, the VO2 pellet is post-annealed in a homemade induction furnace at 1300 °C under a controlled atmosphere to allow grain growth by coalescence and improve pellet surface quality. According to a surface topography analysis, the mean amplitude roughness parameter (Ra) of the obtained VO2 ceramic is found to be 2.93 ± 0.01 nm. A large resistance change by three orders of magnitude along the phase transition is observed, which makes the as-prepared smooth VO2 ceramic a promising candidate for various applications requiring optical and/or electronic switching behavior depending on temperature.

International audience

International audience; Additive manufacturing (AM), especially powder bed laser sintering (PBLS), has been an increasingly popular field since the 1980s. Direct SLS is particularly challenging with ceramic materials due to their low thermal conductivity, high melting point, and brittle mechanical behaviour. In addition, they require longer processing times for a reliable sintering degree. In this work, the impact of some crucial parameters in SLS applied to a copper-doped hydroxyapatite bioceramic was studied. Incorporating copper ions into the hydroxyapatite matrix by thermal treatment can stimulate blood vessel formation, simultaneously improving the material's mechanical integrity and antibacterial properties. Moreover, it facilitates laser power absorption by the material at the laser wavelength. Thin films were prepared with controlled thicknesses using dip-coating on glass substrates, and they were irradiated by an ytterbium laser (1.070 µm wavelength). Experimental laser irradiation was systematically compared to numerical models to predict the maximum temperature produced on the film surface by laser irradiation. The evaluated parameters are the absorptivity from the copper concentration, the film thickness, and the laser source (scanning velocity and power). Combining low laser scanning speeds with low film thickness and optimised absorption tuned by the copper concentration has made possible the development of well-sintered ceramics by the PBLS technique.

Piezoelectric thick films are of real interest for devices such as ceramic Micro-ElectroMechanical Systems (MEMS) because they bridge the gap between thin films and bulk ceramics. The basic design of MEMS includes electrodes, a functional material, and a substrate, and efforts are currently focused on simplified processes. In this respect, screen-printing combined with a sacrificial layer approach is attractive due to its low cost and the wide range of targeted materials. Both the role and the nature of the sacrificial layer, usually a carbon or mineral type, depend on the process and the final device. First, a sacrificial layer method dedicated to screen-printed thick-film ceramic and LTCC MEMS is presented. Second, the recent processing of piezoelectric thick-film ceramic MEMS using spark plasma sintering combined with a protective layer approach is introduced. Whatever the approach, the focus is on the interdependent effects of the microstructure, chemistry, and strain/stress, which need to be controlled to ensure reliable and performant properties of the multilayer electroceramics. Here the goal is to highlight the benefits and the large perspectives of using sacrificial/protective layers, with an emphasis on the pros and cons of such a strategy when targeting a complex piezoelectric MEMS design.

International audience; Based on the combined corrected chemical analysis, the single-crystal X-ray structural results, and the revised Mössbauer spectral analysis, the best formulation of Li1.4(1)[Fe4.4(1)IIFe0.6(1)III(HPO3)6]·1.47(3) H2O, 1b, has been obtained; also, from a revised Mössbauer spectral analysis, a revised formulation of K0.95(5)[Fe3.95(5)IIFe1.05(5)III(HPO3)6]·0.5 H2O, 2m, has been obtained. The revised analysis of the room-temperature Mössbauer spectral parameters for both compounds is consistent with their crystallographic structures and the different nature and occupancies of the Li+ and K+ crystallographic sites. From a detailed analysis of the impedance spectroscopy measurements of Li1.43[Fe4.43IIFe0.57III(HPO3)6]·1.5 H2O, 1, between 123 and 189 °C, two processes involving the electric charge response to the ac electric field have been identified. An activation energy for the charge transfer in 1 of 0.91(2) eV or 7340(160) cm–1 has been obtained; the charge transfer may involve a correlated hopping of the Li+ ion and an electron between the iron(II) and iron(III) ions.

International audience; Pure ionic conductors as solid‐state electrolytes are of high interest in electrochemical energy storage and conversion devices. They systematically involve only one ion as the charge carrier. The association of two mobile ionic species, one positively and the other negatively charged, in a specific network should strongly influence the total ion conduction. Nb5+‐ (4d0) and Ti4+‐based (3d0) derived‐perovskite frameworks containing Na+ and O2− as mobile species are investigated as mixed ion conductors by electrochemical impedance spectroscopy. The design of Na+ blocking layers via sandwiched pellet sintered by spark plasma sintering at high temperatures leads to quantified transport number of both ionic charge carriers tNa+ and tO2−. In the 350–700 °C temperature range, ionic conductivity can be tuned from major Na+ contribution (tNa+ = 88%) for NaNbO3 to pure O2− transport in NaNb0.9Ti0.1O2.95 phase. Such a Ti‐substitution is accompanied with a ≈100‐fold increase in the oxygen conductivity, approaching the best values for pure oxygen conductors in this temperature range. Besides the demonstration of tunable mixed ion conduction with quantifiable cationic and anionic contributions in a single solid‐state structure, a strategy is established from structural analysis to develop other architectures with improved mixed ionic conductivity.

International audience; The design and processing of vibrational energy harvester based on screen-printed piezoelectric lead zirconate titanate (Pb(ZrxTi1-x)O3 (PZT)) are here described. Two different structures, a simple cantilever and a complex zigzag geometry made of PZT layer sandwiched between gold electrodes and supported on a metallic stainless steel substrate have been successfully fabricated by screen printing thick film technique. Compared to bulk PZT ceramics, the main limiting features at different scales are porosity, interfaces and bending issues. The microstructural analysis of the interfaces in the cantilever has highlighted the formation of an interface between the substrate and the bottom electrode which ensures cohesion of the structure but can limit its dynamic. Bending has shown to be dependent on the thickness of the active piezoelectric layer. Dielectric and electromechanical characterizations performed on multilayers, bulk ceramics, and free-standing screen-printed disks are compared and discussed on the basis of interface issues.

International audience

International audience; Interfaces are a major issue when designing ferroelectric nanostructured materials with tailored properties. In a context of integration and multifunctionality in the field of electronics, several strategies have been developed to control the microstructure and defect chemistry of interfaces that strongly impact the macroscopic properties. The suitability of the core-shell approaches that allow a subtle tuning of interface phenomena at different scales has been widely demonstrated. We focus here on the flexibility of the core-shell approach devoted to the processing of nanostructured ferroelectric composites. Our strategy relies on the use of advanced synthesis processes to design ferroelectric grains coated with shells of different nature, morphology and crystallinity. Typical examples will be reviewed with a specific attention on their impact on both microstructure and dielectric properties. Our approach, based also on the use of fast sintering technique, provides a guidance to design 3D bulk nanostructured ferroelectrics while controlling and/or exploiting size, interface and defects chemistry. The contribution of specific spectroscopies to probe interfacial chemistry and defects is underlined. The high density of interfaces in core-shell materials is obviously an advantage to target additional functionality such as magneto-electric coupling. This is illustrated in 3D composites and one dimensional nanostructures that coaxially combine electric and magnetic materials. The core-shell approach described here could be transferred to a much broader range of materials covering many functionalities provided a deeper understanding of the interfaces at the atomic scale is achieved and a further development of low temperature processing is reached.

An innovative new system under high pressure syntheses activated by pulsed electric current (HP-SPS) was designed and built in-house with belt type apparatus (HP-SPS-Belt). This new HP-SPS- Belt with large volume chamber is capable of reaching high pressures up to 6 GPa and temperatures until 1800 °C. This system was pressure and temperature calibrated by using different metal calibrants. To demonstrate the efficiency of this new equipment in the present work, we have successfully shown the structural γ to α phase transformation in alumina under less severe conditions than in conventional high pressure and temperature processes. Further, we have also used this new HP-SPS-Belt to fabricate shear cutter for drilling bits in an economical way of fabrication. This study shows the wide interest of our unique designed equipment for various applications in materials processing to better control their microstructure and their properties. Keywords: High pressure, High temperature, Pulsed electric current, High-pressure spark plasma sintering (HP SPS), shear cutter for drilling bits and alumina

International audience; The spark plasma sintering (SPS) of Eu 3+-doped Y 3NbO 7 niobate phase was investigated to obtain dense ceramics. Although SPS allowed obtaining high-density ceramics, decomposition of the niobate phase occurred at high temperature and was promoted by the SPS process, which limited its use as an optical material. The niobate phase has been prepared by two synthesis methods: a solid-state route and a sol–gel method. The purity, density and microstructure of the dense ceramics were analyzed after spark plasma sintering. Translucent ceramics were only obtained from sol–gel powders after SPS at 1600 °C during 20 min with a heating rate of 5 °C/min. The sintering study of the pure niobate phase showed that during SPS process and especially in the presence of the high electrical field the Y 3NbO 7 phase is metastable at 1600 °C. A decomposition of the niobate compound is clearly demonstrated by luminescence measurements when high heating rates were used.

National audience

International audience; Cool-SPS conditions (low temperature/high pressure) can be used to densify materials with limited thermodynamical stability, due to low temperature phase transition, melting, decomposition… We recently demonstrated the potential of SPS for the stabilization and densification of diversified materials at very low temperatures. Here we report the sintering of a potentially magnetoelectric pyrophosphate with low temperature decomposition. Characterization of its magnetic properties are presented, and dielectric/magnetoelectric characterization could also be performed thanks to the high densification obtained at temperatures as low as 200 °C.

International audience; NaNb1–xTixO3–0.5x (0 < x ≤ 0.15) compounds were prepared using a two-step synthesis process involving a hydrothermal route at T = 200 °C in an autoclave followed by heat treatments under air or reductive conditions. Rietveld structural refinements from X-ray diffraction data combined with 23Na and 93Nb nuclear magnetic resonance evidenced the formation of new complex oxides crystallizing in the P21ma space group. Ti substitution for Nb atoms contributes to stabilize the acentric polymorph rather than the well-known thermodynamically stabilized network (Pbma space group) of sodium niobate. Taking into account the competitive bond sequence Na1(2)–O1(2)–Nb–O3(4), the large variation of Na1–O1 and Na2–O2 bond lengths after Ti substitution leads to reduction of the Nb/Ti–O1 and Nb/Ti–O2 apical distortion (elongation in one direction) and consequently exaltation of the distortion in the equatorial plane. Then, transition metal crystal field splitting, as well as the second-order Jahn–Teller effect, increases, and the optical band gap red-shifts to visible range starting with low Ti content. Two phase transition sequences at moderated temperature are characterized by the relaxation of the perovskite framework with various [Nb(Ti)O6] octahedral distortion and tilt modes: from the polar orthorhombic P21ma phase to the centrosymmetric orthorhombic Cmcm network above T = 300 °C and then to the ideal cubic perovskite structure above T = 600 °C. The pronounced decrease in phase transition temperature with Ti substitution, especially from P21ma to Cmcm, was correlated to the almost identical stabilities of the two Na sites and four oxygen positions in P21ma symmetry but also to larger distortion of the transition metal polyhedron enhancing the oxygen mobility. Moreover, the high ionic conductivity of oxygen-deficient NaNb1–xTixO3–0.5x was evidenced for the first time between 300 and 700 °C (σion (T = 300 °C) = 3 × 10–5 S·cm–1 and σion (T = 700 °C) = 2 × 10–3 S·cm–1, for x = 0.15).

International audience; Autonomous electronic devices and increasing use of wireless sensors, which are more and more effective, are facing the problem of energy autonomy. This autonomy can be achieved with preliminary storage and/or energy harvesting. Hence, for 20 years, the energy harvesting research field has intensively focused on the development of new materials and their integration in micro/nanogenerators. In this research area, Micro-Electromechanical System (MEMS) energy harvesters (EH) using piezoelectric materials is one of the most promising options, because of the availability of mechanical vibrations and of the simplicity of electromechanical conversion. Piezoelectric ceramics, commonly used in various applications, are attractive for EH, and among them, Pb(Zr1-xTix)O3 (PZT), despite its lead content, remains mostly studied because of its outstanding properties. For its ceramic process, the main objectives are improved densification, cost and energy efficient processing, and integration in microgenerators. In this context, SPS sintering of printed electrode PZT piezoelectric layers supported on stainless steel substrate (SS) is highly challenging. In this chapter, after a section devoted to piezoelectric EH, the device made of screen-printed PZT layers on SS substrate is presented. Then, the authors focus on the strategy to achieve, in one step, a cantilever transducer where the printed electrode PZT and the SS substrate are co-sintered by SPS. As a first part of this ambitious objective, microstructural, dielectric, and piezoelectric properties of the PZT pellet densified by SPS are presented and compared to PZT printed layers conventionally sintered.

Monocrystalline titanium dioxide (TiO2) micro-spheres support two orthogonal magnetic dipole modes at terahertz (THz) frequencies due to strong dielectric anisotropy. For the first time, we experimentally detected the splitting of the first Mie mode in spheres of radii inline imagem through near-field time-domain THz spectroscopy. By fitting the Fano lineshape model to the experimentally obtained spectra of the electric field detected by the sub-wavelength aperture probe, we found that the magnetic dipole resonances in TiO2 spheres have narrow linewidths of only tens of gigahertz. Anisotropic TiO2 micro-resonators can be used to enhance the interplay of magnetic and electric dipole resonances in the emerging THz all-dielectric metamaterial technology.

International audience; Inspired from the microstructure of natural biological materials, a laminated titanium material was successfully elaborated using a novel approach of “flakes powder metallurgy.” Ti flakes powders, used as building blocks of the layers microstructure, were prepared by ball milling. They were then assembled into fully dense laminated materials using the spark plasma sintering technique. The results show (1) an anisotropy microstructure of the sintered material prepared from the flakes powder, (2) 15% of contribution of the lamellar architecture to the strength (hardness) of the material, and (3) faster densification of the flakes powder compared to unmilled powder.

International audience; The re-oxidation kinetics of BaTiO3 ceramics sintered by Spark Plasma Sintering (SPS) was investigated using in-situ impedance spectroscopy. Thanks to the flexibility of the SPS process, the grain size of the dense ceramics was tuned from 0.5 μm to 10 μm. The re-oxidation kinetics are found to be very fast regardless of the grain size and a full re-oxidation of the ceramics are achieved after 20 h of exposure to an ambient environment at only 600 °C. The residual density of charge carriers is reduced when using finer starting powders. SPS ceramics made with micrometer size grains demonstrate a residual charge-carrier density that is one tenth that of ceramics made from 10 μm particles. Grain-boundary conduction is dominant through fine-grain SPS ceramics. This latter feature is similar to BaTiO3 sintered using the conventional route with 10 μm size grain. Finally, the critical grain size for optimal dielectric permittivity is found to shift from 0.7 μm in standard ceramics to 1.5 μm in SPS ceramics.

We show that the type-II multiferroic properties of bulk MnWO4 are kept in nanostructured ceramics of 50 nm grain size prepared via spark plasma sintering (SPS). This means that ferroelectric polarization is robust against downsizing, which is at variance with standard ferroelectrics like BaTiO3. We ascribe this stability to the spin-driven nature of the ferroe-lectric correlations in type-II multiferroics while it is resulting from lattice distortion in other cases. This may open the way for persistent type-II multiferroicity with no need for external stabilization like substrate-generated strain.

International audience; Dense ceramics of MnSO4 composition have been successfully densified at 400 °C in only 5 min under a uniaxial pressure of 400 MPa, using Spark Plasma Sintering technique. Since the stable form of MnSO4 in ambient atmosphere is its hydrate MnSO4·H2O, crystallizing in a different space group, dehydration is required to reach a purely anhydrous phase. In situ dehydration during Spark Plasma Sintering allows to lower both sintering temperature and time. Applied pressure strongly influences dehydration step and therefore is a key parameter to tune densification, so far as to obtain a dense MnSO4·H2O ceramic. The presence of a reversible phase transition to a β-MnSO4 high temperature form seems to influence the dehydration temperature under pressure, and likely drives the sintering mechanisms. The high densification obtained, beyond 95% of theoretical density, added to the preservation of the structural and physical properties of MnSO4 after sintering allowed to perform reliable and reproducible measurements showing a dielectric anomaly associated to the magnetic transition, and the hysteretic behaviour of capacitance versus magnetic field, which is a clue for an intrinsic magnetoelectric coupling in MnSO4.

This paper addresses for the first time two of the main challenges in the field of electroceramics. The first one is the development of a continuous, fast and reliable synthesis method for producing sub-20 nm barium titanate zirconate (BaTi1-yZryO3 with 0 ≤ y ≤ 1–BTZ) nanocrystals over the whole solid solution, while keeping a narrow size distribution. The second one concerns the processing of dense and nanostructured lead free electroceramics highlighting the size effect on the crossover from ferroelectric to relaxor, in the case of grains smaller than 100 nm. This was achieved combining the supercritical fluid technology to produce in continuous and at moderate temperature (400 °C) BTZ nanocrystals, with Spark Plasma Sintering (SPS) to prevent grain growth during the sintering. Keywords: Barium titanate zirconate (BTZ), Supercritical fluid, Nanocrystal, Nanostructured ceramic, Lead free, Ferroelectric, Relaxor

We demonstrate a binocular holographic display with an amplitude-only spatial light modulator (SLM), which enables us to display a 3D scene with much higher frame rate than the case of a conventional stereoscopic 3D. Instead of dividing either frames or pixels for assigning the left and right images, we divide the space near pupils by modulating the phase of a computer generated hologram.

International audience; A reliable and flexible synthesis route was used for processing high density Ni–BaTiO3 nanocable arrays based on wet chemical impregnation and subsequent electrodeposition within a highly ordered unidirectional porous alumina membrane. The core–shell structure was carefully investigated by bright field scanning transmission electronic microscopy coupled with energy dispersive X-ray spectroscopy. The strength of the dipolar interaction arising from the packing density of the magnetic nanowires was correlated with the BaTiO3 wall thickness through magnetometry and ferromagnetic resonance measurements. Our approach opens a pathway to obtain optimized nanostructured multiferroic composites exhibiting tunable magnetic properties.

The defective fluorite-related Y

International audience; The defective fluorite-related Y3NbO7 host lattice was doped with Eu(3+) ions to understand the influence of spark plasma sintering (SPS) process on this host lattice. The intrinsic disorder due to the occurrence of oxygen vacancies results in amorphous-type responses of the luminescent cations, and the spectral distribution varies as a function of the niobium content. Two spectral fingerprints of europium emissions were clearly enhanced. The correlation between luminescence, X-ray diffraction, and electron diffraction characterizations shows the existence of local inhomogeneity. Indeed, the particular nonequilibrium sintering conditions allowed pointing out a lack of miscibility within the Y3NbO7 solid solution domain. Thus, the SPS pellet is a composite of two extreme compositions. This phase demixing is mainly induced by the pressure coupled with a current effect that makes possible ionic migration in this Y3NbO7 ionic conductive matrix.

The article discusses the progress and issues related to transparent oxide semiconductor (TOS) TFTs for advanced display and imaging applications. Amorphous oxide semiconductors continue to spark new technological developments in transparent electronics on a multitude of non-conventional substrates. Applications range from high-frame-rate interactive displays with embedded imaging to flexible electronics, where speed and transparency are essential requirements. TOS TFTs exhibit high transparency as well as high electron mobility even when fabricated at room temperature. Compared to conventional a-Si TFT technology, TOS TFTs have higher mobility and sufficiently good uniformity over large areas, similar in many ways to LTPS TFTs. Moreover, because the amorphous oxide semiconductor has higher mobility compared to that of conventional a-Si TFT technology, this allows higher-frame-rate display operation. This would greatly benefit OLED displays in particular because of the need for lower-cost higher-mobility analog circuits at every subpixel.

To replace conventional Al heavy wire bonding in interconnecting power devices, we have explored the use of Cu heavy wire bonding, which offers superior electrical, mechanical, and thermal properties compared to Al wires that leads to better interconnection reliability. Chip pad metallizations that are strong enough to support Cu wires firmly against chip pads and endure high bonding parameters were first evaluated by 3D finite element modeling (FEM) of the Cu heavy wire bonding process. The FEM results indicated that an electroless plated Ni layer may be used as the primary candidate for the pad metallization of Cu heavy wire bonding because it enables the reinforcement of standard Al pads in power devices and allows for metallurgical interaction with Cu wires. Further, the deposition of the Ni layer entailed a simple protocol. The three major bonding parameters including force, ultrasonic energy, and time were optimized to achieve successful wire bonding of 300-μm-thick Cu wires to pads strengthened with Ni layers in power devices. Microstructures and compositions of the bonded interface were analyzed by transmission electron microscopy, which provided insight into the bonding characteristics between the Cu wires and the Ni pads. Reliability tests of the bonding were also carried out by the thermal shock test and pressure cooker test.

Dielectric terahertz (THz) resonators of sub-wavelength size, as compared to free-space wavelength at resonance, are essential building blocks for the emerging all-dielectric THz technology. We experimentally and numerically study the effects of material anisotropy in THz dielectric spheres made of mono-crystalline titanium dioxide (TiO 2 ). We measured the THz response of anisotropic dielectric micro-spheres using near-field THz time-domain spectroscopy. We experimentally demonstrate the splitting of narrow magnetic dipole resonances, corresponding to ordinary and extraordinary Mie modes, attributed to strong material anisotropy. We study ensembles of mono-crystalline TiO 2 spheres that can be used as advanced meta-atom designs for THz metamaterials technology.

Using the near-field time-domain terahertz spectroscopy, we detect the splitting of magnetic dipole resonance mode in strongly anisotropic mono-crystalline TiO 2 micro-spheres. By fitting the Fano resonance model to the experimental data, we extract the intrinsic resonant properties of the micro-spheres and characterise their constituent dielectric material.

International audience; All-oxide composites are increasingly investigated in the field of microelectronics and telecommunications because of their multifunctionalities. Advanced control of interfaces is required to fully tune the macroscopic properties of the composites. Processing ferroelectric Ba0.65Sr0.35TiO3 (BST65/35)-TiO2 composites by Spark Plasma Sintering (SPS), we show that the SPS electric current promotes an interphase growth whose thickness depends on the BST/TiO2 stacking and on the current direction. In all cases, the interface is composed of Ba1.14(2) Ti8O16-δ a highly defective, but stable phase which can be used to tune the overall dielectric properties of the composites.

In recent years, resistance changes random access memory (RRAM) which shows reversible bistable resistance states by applied voltage has been studied as one of the alternatives of next-generation nonvolatile memory due to its excellent device characteristics including scalability, speed, and retention. Here, we report on the noncharge-based NiO RRAM device characteristics with load resistor as well as the simulation results of controlled conducting filament configuration. The RRAM device with load resistor showed super performances including highly reduction of switching current (~1 order) and significantly improved switching voltage distribution (30% reduction).

This paper discusses progress and issues related to amorphous oxide semiconductors (AOS) thin film transistors (TFTs) for flat panel display and imaging applications. In particular, we review the dark- and wavelength-dependent photo-instability in AOS TFTs and its origins, along with the density of states (DOS) profile in these materials, including the role of oxygen vacancies. The relative dominance of trap-limited conduction (TLC) and percolation depending on gate voltage is presented. The effects of photo-instability and specifically persistent photoconductivity (PPC) arising from ionized oxygen vacancies is examined using results of stress/recovery measurements. Based on this, techniques to overcome the PPC are presented, and includes a dual gate photo-TFT structure with appropriate pulse biasing.

S.-E. Ahn Samsung Advanced Institute of TechnologySamsung Electronics CorporationsYongin-Si, Gyeonggi-Do 446-712 KoreaSchool of electrical engineeringKorea UniversitySeoul 136-701, Korea Dr. I. Song , Dr. S. Jeon , W Jeon , . . Y Kim , . Y Dr. C. Kim , Dr. B. Ryu , Dr. U.-I. Chung Samsung Advanced Institute of TechnologySamsung Electronics CorporationsYongin-Si, Gyeonggi-Do 446-712, KoreaE-mail: sanghun1.jeon@samsung.com Dr. J.-H. Lee Liquid Crystal Display R&D CenterSamsung Electronics CorporationsYongin-Si, Gyeonggi-Do 446-712, Korea Prof. A. Nathan Centre for Advanced Photonics and ElectronicsDepartment of EngineeringCambridge UniversityCambridge CB3 0FA, UKE-mail an299@cam.ac.uk S. Lee London Centre for NanotechnologyUniversity College LondonLondon WC1H 0AH, UK Prof. G. Kim . T School of electrical engineeringKorea UniversitySeoul 136-701, Korea

The composition of amorphous oxide semiconductors, which are well known for their optical transparency, can be tailored to enhance their absorption and induce photoconductivity for irradiation with green, and shorter wavelength light. In principle, amorphous oxide semiconductor-based thin-film photoconductors could hence be applied as photosensors. However, their photoconductivity persists for hours after illumination has been removed, which severely degrades the response time and the frame rate of oxide-based sensor arrays. We have solved the problem of persistent photoconductivity (PPC) by developing a gated amorphous oxide semiconductor photo thin-film transistor (photo-TFT) that can provide direct control over the position of the Fermi level in the active layer. Applying a short-duration (10 ns) voltage pulse to these devices induces electron accumulation and accelerates their recombination with ionized oxygen vacancy sites, which are thought to cause PPC. We have integrated these photo-TFTs in a transparent active-matrix photosensor array that can be operated at high frame rates and that has potential applications in contact-free interactive displays.

The three-dimensionally alternating integration of stackable logic devices with memory cells represents a revolutionary approach to the fabrication of extremely high density memory devices. Conventional silicon-based memory devices face impending limits if they are progressively scaled toward smaller-sized features. Here, we present a high-density memory architecture that utilizes electronically active oxide thin-film transistors (TFTs) combined with memory elements such as vertical NAND and resistive random access memory devices. High-mobility [~μsaturation of 20 cm2/(eV·s)] oxide TFTs with amorphous Hf-In-Zn-O performs fairly well as a decoder, a driver, a sense amplifier, and a latch, and the core elements that are required for 3-D logic circuits. With these logic circuit elements, memory density can be considerably increased up to tens of terabits due to the significantly reduced interconnection lines and logic circuit areas in the bottom silicon layer. This approach can serve as a useful strategy for the development of high-density memory devices.

Present charge-based silicon memories are unlikely to reach terabit densities because of scaling limits. As the feature size of memory shrinks to just tens of nanometers, there is insufficient volume available to store charge.(1) Also, process temperatures higher than 800 °C make silicon incompatible with three-dimensional (3D) stacking structures. Here we present a device unit consisting of all NiO storage and switch elements for multilevel terabit nonvolatile random access memory using resistance switching.(2-5) It is demonstrated that NiO films are scalable to around 30 nm and compatible with multilevel cell technology. The device unit can be a building block for 3D stacking structure because of its simple structure and constituent, high performance, and process temperature lower than 300 °C. Memory resistance switching of NiO storage element is accompanied by an increase in density of grain boundary while threshold resistance switching of NiO switch element is controlled by current flowing through NiO...

Numerous candidates attempting to replace Si-based flash memory have failed for a variety of reasons over the years. Oxide-based resistance memory and the related memristor have succeeded in surpassing the specifications for a number of device requirements. However, a material or device structure that satisfies high-density, switching-speed, endurance, retention and most importantly power-consumption criteria has yet to be announced. In this work we demonstrate a TaO(x)-based asymmetric passive switching device with which we were able to localize resistance switching and satisfy all aforementioned requirements. In particular, the reduction of switching current drastically reduces power consumption and results in extreme cycling endurances of over 10(12). Along with the 10 ns switching times, this allows for possible applications to the working-memory space as well. Furthermore, by combining two such devices each with an intrinsic Schottky barrier we eliminate any need for a discrete transistor or diode in solving issues of stray leakage current paths in high-density crossbar arrays.