A5102757641- Ferroelectric and Piezoelectric Materials
- Advanced Memory and Neural Computing
- Transition Metal Oxide Nanomaterials
- Acoustic Wave Resonator Technologies
- Semiconductor materials and devices
- Ferroelectric and Negative Capacitance Devices
- CCD and CMOS Imaging Sensors
- Microwave Dielectric Ceramics Synthesis
- Electronic and Structural Properties of Oxides
- Plasma Diagnostics and Applications
- Copper Interconnects and Reliability
- Gas Sensing Nanomaterials and Sensors
- Conducting polymers and applications
- Nanowire Synthesis and Applications
- Phase-change materials and chalcogenides
- Photorefractive and Nonlinear Optics
- Advanced Sensor and Energy Harvesting Materials
- Anodic Oxide Films and Nanostructures
- Multiferroics and related materials
- Advancements in Photolithography Techniques
- High voltage insulation and dielectric phenomena
- Shape Memory Alloy Transformations
- Carbon Nanotubes in Composites
- Ultrasonics and Acoustic Wave Propagation
- Luminescence Properties of Advanced Materials
Pohang University of Science and Technology
2017-2019
Samsung (South Korea)
2002-2015
Samsung Advanced Institute of Technology (South Korea)
2014
Oak Ridge National Laboratory
2014
University of Puerto Rico System
2014
Universidade Estadual Paulista (Unesp)
2014
Universidade de São Paulo
2014
Samsung (United States)
2003-2006
Inha University
2004
Virginia Tech
1987-2003
Negative resistance behavior and reproducible switching were found in polycrystalline NiO films deposited by dc magnetron reactive sputtering methods. Oxygen to argon gas ratio during deposition was critical deciding the detailed characteristics of either bi-stable memory or mono-stable threshold switching. Both metallic nickel defects vacancies influenced negative characteristics. We obtained a distribution low values which dependent on compliance current high-to-low At 200°C,...
Experimental results on the bistable resistive memory switching in submicron sized NiO cells are presented. By using a current-bias method, intermediate resistance states and anomalous fluctuations between observed during transition from high state to low state. They interpreted be associated with filamentary conducting paths their formation rupture for origin NiO. The experimental discussed basis of conductions consideration local Joule heating effect.
Simple binary-TMO (transition metal oxide) resistive random access memory named as OxRRAM has been fully integrated with 0.18/spl mu/m CMOS technology, and its device well cell properties are reported for the first time. We confirmed that is highly compatible conventional process such no other dedicated facility or necessary. Filamentary current paths, which switched on off by asymmetric unipolar voltage pulses, made insensitive to contact size promising high scalability. Also, showed...
We propose a HfZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> (HZO)-based ferroelectric synapse device with multi-levels states of remnant polarization that is equivalent to conductance states. By optimizing the pulse condition, we obtained 32 levels for both potentiation and depression. Furthermore, field-effect transistor simulated using multiple The simulation results show linear symmetric can be by applying optimum...
Ferroelectric materials are promising candidates for synaptic weight elements in neural network hardware because of their nonvolatile multilevel memory effect. This feature is crucial use mobile applications such as inference when vector matrix multiplication performed during portable artificial intelligence service. In addition, the adaptive learning effect ferroelectric polarization has gained considerable research attention reducing CMOS circuit overhead an integrator and amplifier with...
For the development of resistive memory devices using NiO, improvements several switching properties are required. In NiO cells with noble metal electrodes, broad dispersions parameters generally observed continuous switchings. We report in minimizing all thin IrO2 layers between and electrodes. The role on growth stabilization discussed.
The effects of various metal electrodes on the resistive switching NiO thin films were investigated. Contrary to belief that Pt is used for its high work function, which enables Ohmic contact p-type NiO, was observed in with Ta or Al a low function as-deposited state. Ag Cu top electrode and free energy oxidation shows importance formation an oxide layer at metal/NiO interface.
A quantitative fatigue model is proposed for ferroelectric thin films on the basis of effective one-directional movement defects due to asymmetric polarization under alternating pulses, defect entrapment at electrode-ferroelectric interface (and/or grain and domain boundaries), resultant loss these surfaces structural damage. equation derived in accordance with this three parameters such as initial saturation polarization, piling constant, decay constant are defined. The predicted values...
Conductivity switching phenomena controlled by external voltages have been investigated for various NiO films deposited dc reactive sputtering methods. Pt∕NiO∕Pt capacitor structures with top electrodes of different diameters showed increasing off-state current the diameter a electrode and nearly same on-state independent diameter. Local conductivity behaviors observed in series structure consisting two capacitors resistance values. By reasoning out mechanisms from characteristics...
The resistance switching behavior and mechanism of nonstoichiometric zirconium oxide thin films were investigated for nonvolatile memory application. Pt/ZrO/sub x//p/sup +/-Si sandwich structure fabricated by reactive sputtering shows two stable states. By applying proper bias, from one to another state can be obtained. composition in ZrO/sub x/ confirmed X-ray photoelectron spectroscope (XPS) analysis, which showed three layers such as top stoichiometric 2/ layer with high resistance,...
Abstract Electrochemical models of failure in oxide perovskite materials are reviewed. It is noted that oxygen vacancies a common source electrical degradation, fatigue, and ageing. Taking the behavior into account, semi-quantitative model for time dependent dielectric breakdown (TDDB) proposed quantitative fatigue mechanism discussed ferroelectric thin films. Based on theory, recent improvement films presented. Correlation between leakage current also
We investigated resistance switching in top-electrode/NiO∕Pt structures where the top electrode was Au, Pt, Ti, or Al. For Pt∕NiO∕Pt and Au∕NiO∕Pt with ohmic contacts, effective electric field inside film high enough to induce trapping detrapping at defect states thus switching. a Ti∕NiO∕Pt structure well-defined Schottky contact Ti∕NiO interface accompanied by an appreciable voltage drop, NiO not Al∕NiO∕Pt low barrier Al∕NiO interface, could be induced higher since drop negligible but small.
We investigate the effects of high-pressure hydrogen annealing (HPHA) on W/ferroelectric Al:HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /interface layer (IL)/Si stacks. With HPHA, degradation in remnant polarization is observed pristine state due to ferroelectric domain pinning. However, after wake-up, a comparable by de-pinning. In addition, HPHA improves quality current and low interface trap density are maintained up 10 <sup...
Highly ordered, vertical carbon nanotubes (CNTs) (see Figure) have been grown on a pre-patterned, porous anodic aluminum oxide (AAO) template using lithographic patterning method and thermal chemical vapor deposition. The AAO itself plays catalytic role in CNT growth the crystallinity of CNTs is strongly influenced by presence cobalt particles at bottom pores.
The effects of Ni and Ni0.83Pt0.17 alloy electrodes on the resistance switching dc-sputtered polycrystalline NiO thin films were investigated. initial off-state resistances similar to that Pt∕NiO∕Pt film. However, after first cycle switching, significantly decreased in with electrode. It can be attributed migration from films. improvement data dispersion parameters is explained terms decrease effective thickness resulting Ni.
Epitaxial NiO films have been fabricated on SrRuO3 prepared SrTiO3 single-crystal substrates. The x-ray diffraction spectra and transmission electron microscopy confirm the epitaxial growth of with atomically flat surfaces SRO electrode. I-V measurements show resistive memory switching behavior a change in polarity voltage bias, contrast polycrystalline by single polarity. characteristics under various synthesis conditions electrodes are presented, which suggests an important role interfaces...
In order to investigate the mechanism behind bistable resistance switching in NiO thin films, we have done detailed x-ray photon spectroscopy (XPS) and diffraction Analysis (XRD) on Ti doped samples fabricated under various conditions. We discovered that a high initial resistivity was required for undergo switching, presence of metallic Ni content these determined by XPS. XRD data also showed grown with relative (200) orientation preferred over those (111) orientation.
The behavior of unipolar resistance switching in NiO thin film was investigated. current and the voltage alone did not follow statistical distribution. Instead, it observed that product voltage; namely, power follows Poisson’s An electrical manipulation—pulse train, for example—was suggested order to minimize failure based on above distribution behavior.
A resistance-switching model in nickel oxide thin film is proposed based on Poisson distribution of electrical switching power. Conductive percolating network soft breakdown surface may be the source resistance switching. The main body remain unchanged, but a portion broken and healed repeatedly during Dependence reset current electrode area explained by fractal dimension.
Carbon nanotube morphology has been engineered via simple control of applied voltage during dc plasma chemical vapor deposition growth. Below a critical voltage, configuration vertically aligned tubes with constant diameter is obtained. Above the nanocone-type The strongly field-dependent transition in attributed primarily to etching and decrease size nanotube-nucleating catalyst particles. A two-step allows creation dual-structured consisting broad base nanocone (∼200nm dia.) small (∼7nm)...
We have measured the DC resistance R ( T ) and AC dielectric constant ε (ω) for bistable high- low- states of NiO thin film. The state shows thermally activated Debye relaxation (ω). In state, exhibits a metallic temperature dependence (300 K)/ (5 K)=1.6. value is drastically different from that we interpret it in terms free-carrier Drude response. plasma frequency ω p 2 estimated to be 1.2×10 9 /cm 3 .