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The perpendicular-spin-transfer-torque magnetic-tunnel-junction neuron exhibited integrate behaviour depending on the nanoscale grain size of the MgO tunnelling barrier showing possibility for spiking neural network applications.

We propose a two-step hydrogen-ion implantation approach for realizing crystalline-defect-free Si1-xGex channels for potential use in gate-all-around field-effect-transistors beyond the 3 nm transistor-design rule. A dislocation sink was created in a projected range of ion implantation 100 and 200 nm above the strain-relaxed Si0.7Ge0.3 layer and Si substrate interface using two-step H+ -ion implantation. Doses of 5 × 1015 and 2 × 1015 atoms/cm2 were used at 100 and 200 nm, respectively, above the interface, and post-annealing was performed at 800 °C for 30 min. The two-step implantation annihilated the misfit and threading dislocations near the relaxed Si0.7Ge0.3/Si interface. The annihilation efficiency strongly depended on the location and second ion dose of the implantation: the maximum annihilation efficiency was obtained at 100 and 200 nm above the interface with multiple H+-ion doses of 5 × and 2 × 1015 atoms/cm2.

Face-centered-cubic crystallized super-fine (~ 2 nm in size) wet-ceria-abrasives are synthesized using a novel wet precipitation process that comprises a Ce4+ precursor, C3H4N2 catalyst, and NaOH titrant for a synthesized termination process at temperature of at temperature of 25 °C. This process overcomes the limitations of chemical–mechanical-planarization (CMP)-induced scratches from conventional dry ceria abrasives with irregular surfaces or wet ceria abrasives with crystalline facets in nanoscale semiconductor devices. The chemical composition of super-fine wet ceria abrasives depends on the synthesis termination pH, that is, Ce(OH)4 abrasives at a pH of 4.0–5.0 and a mixture of CeO2 and Ce(OH)4 abrasives at a pH of 5.5–6.5. The Ce(OH)4 abrasives demonstrate better abrasive stability in the SiO2-film CMP slurry than the CeO2 abrasives and produce a minimum abrasive zeta potential (~ 12 mV) and a minimum secondary abrasive size (~ 130 nm) at the synthesis termination pH of 5.0. Additionally, the abrasive stability of the SiO2-film CMP slurry that includes super-fine wet ceria abrasives is notably sensitive to the CMP slurry pH; the best abrasive stability (i.e., a minimum secondary abrasive size of ~ 130 nm) is observed at a specific pH (6.0). As a result, a maximum SiO2-film polishing rate (~ 524 nm/min) is achieved at pH 6.0, and the surface is free of stick-and-slip type scratches.

In this study, a novel chemical–mechanical planarization (CMP) slurry that can perform self-stop polishing was designed. The essential aspects for self-stop polishing are precise design of a nonionic polymer type, molecular weight, and molecular concentration of a self-stopping chemical agent. A good example is polyvinylpyrrolidone (PVP) with a molecular weight of 1300 k and molecular concentration of 0.3 wt%. In this chemical design, the adsorption of a polymer hindrance layer on the surface film topography during CMP can become sufficient under self-stop conditions such as a specific polishing time (e.g., 4 min). The self-stop polishing mechanism is associated with the presence of a relative local pressure difference on the surface film topography. The proper adsorption of the polymer hindrance layer on the surface topography can achieve a uniform relative local pressure distribution globally, and the film polishing rate can achieve adequate planarization of the surface film topography.

The multi‐level feature of GeTe/Sb2Te3 interfacial phase change memory was achieved by applying a designed voltage‐based pulse. It stably demonstrated five multi‐level states without interference for 90 cycles by varying the pulse width. GeTe/Sb2Te3 interfacial phase change memory demonstrated retention time of > 1.0 × 103 s, presenting the significantly low drift coefficient (ν) of

The learning and inference efficiencies of an artificial neural network represented by a cross-point synaptic memristor array can be achieved using a selector, with high selectivity (I

An amorphous (α) indium-gallium-zinc-oxide (IGZO) thin-film-transistor (TFT) was developed as a precise ultraviolet-light (UV-light) sensor, which is extremely sensitive to photoconductivity. A higher absorption of UV-light via a longer UV-light irradiation time and a higher UV-light intensity shifted the threshold voltage (Vth) to a negatively higher voltage and then saturated above a specific UV-light irradiation time. Particularly, the photoconductivity (i.e., Vth) shifts were evidently dependent on the oxygen vacancy (VO)-induced defect density of an ALD α-IGZO channel; in turn, a higher VO-induced defect density led to a higher photoconductivity shift. Additionally, the Vth saturation time in an ALD α-IGZO TFT decreased rapidly with increasing UV-light intensity; in particular, a higher VO-induced defect density presented a smaller decay constant of the Vth saturation time. Furthermore, the Vth after stopping the UV-light irradiation was rapidly recovered to the condition as without UV-light irradiation condition and a higher VO-induced defect density exhibited a longer recovery time.

In 3-dimensional memories such as NAND flash and cross-point memory, the integration fabrication processes face a notable initial-step-height of an isolated SiO2-film deposition, which is an extremely critical process removing such initial-step-height perfectly via chemical mechanical planarization (CMP). The SiO2-film polishing-rate difference was generated between upper and lower locations of initial-step-height and was evidently depended on the nano-ceria abrasive size in an isolated SiO2-film CMP slurry; that is, the polishing ratio of the upper location to lower location remarkably increased from 4.5:1 to 11.5:1, as the ceria abrasive size increased from 21.3 to 81.0 nm. The difference of polishing rate was associated with a local pressure difference between upper and lower locations of initial-step-height; that is, the local pressure at the upper location remarkably increased from 5.2 to 14.2 PSI, while it at the lower location very slightly decreased from 1.0 to 1.3 PSI, as the ceria abrasive size increase from 21.3 to 81.0 nm. Thus, a larger ceria abrasive size in an isolated SiO2-film CMP slurry led to better removal ability (i.e., a shorter polishing time of initial-step-height and a thicker remaining isolated SiO2-film thickness).

The relationship of free surface area with temperature, power, and oxygen concentration in a silicon ingot grown by Czochralski method for solar cells was investigated by simulating the growing process of 4-, 6-, and 8-inch diameter ingots with a 24-inch quartz crucible. It was confirmed that the temperature at auto-temperature-control (ATC) sensor of 4-inch diameter ingot was higher than 6- and 8-inch diameter ingot due to the longer distance between triple point and ATC sensor, i.e., larger area of the free surface. In addition, it was observed that the power consumption for growing 4-inch diameter ingot was greater than 6-and 8-inch diameter ingot because of its smaller heat capacity resulted from smaller charge size. In particular, it was confirmed that the oxygen concentration of 4-inch diameter ingot was lower than those of 6- and 8-inch diameter ingots since the larger free surface area and weaker melt convection led to the lower oxygen concentration in 4-inch ingot. This understanding of the relationship of free surface area with oxygen concentration in a silicon ingot can be applicable directly to control oxygen concentration in growing different diameter of silicon ingots.

For achieving a highly selective polishing rate between a tungsten (W) film and a silicon-dioxide (SiO2) film in W chemical-mechanical planarization (CMP), we designed W-film CMP slurry by mixing a small-molecule having two carboxylic functional groups (i.e., malic acid) as a selectivity agent. The selectivity was principally controlled by the malic acid concentration: it rapidly increased with increasing malic acid concentration in the W-film CMP slurry, and a W-film polishing rate:SiO2-film polishing rate of >100:1 was achieved. We found that the selectivity was mainly determined by the chemical properties, such as the corrosion and the chemical reaction between the films and malic acid rather than by the mechanical property, i.e., the electrostatic force between the ZrO2 abrasive and the films.

Tunnel field-effect transistors (TFETs) have garnered great interest as an option for the replacement of metal–oxide–semiconductor field-effect transistors owing to their extremely low off-current and fast switching suitable for low-power-consumption applications. However, conventional doped TFETs have the disadvantage of introducing undesirable random dopant fluctuation (RDF) events, which cause a large variance in the threshold voltage and ambipolar leakage current at negative gate voltages. In this study, a simple approach for charge plasma-based doping-less TFETs (DL-TFETs), including the Ge/Si bilayer frame, which affects the RDF and low on-current issues, was developed by the commercially available Silvaco Atlas device simulator. The use of the Ge/Si bilayer enhances the on-current and point subthreshold swing to 1.4 × 10−6 A and 16.6 mV dec−1, respectively. In addition, the dependencies of the Ge/Si junction boundary position and Ge content were examined systematically to attain a firm understanding of the electrical features in DL-TFETs.

A Fenton reaction and a corrosion inhibition strategy were designed for enhancing the polishing rate and achieving a corrosion-free Ge1Sb4Te5 film surface during chemical-mechanical planarization (CMP) of three-dimensional (3D) cross-point phase-change random-access memory (PCRAM) cells and 3D cross-point synaptic arrays. The Fenton reaction was conducted with 1,3-propylenediamine tetraacetic acid, ferric ammonium salt (PDTA–Fe) and H2O2. The chemical oxidation degree of GeO2, Sb2O3, and TeO2 evidently increased with the PDTA–Fe concentration in the CMP slurry, such that the polishing rate of the Ge1Sb4Te5 film surface linearly increased with the PDTA–Fe concentration. The addition of a corrosion inhibitor having protonated amine functional groups in the CMP slurry remarkably suppressed the corrosion degree of the Ge1Sb4Te5 film surface after CMP; i.e., the corrosion current of the Ge1Sb4Te5 film surface linearly decreased as the corrosion inhibitor concentration increased. Thus, the proposed Fenton reaction and corrosion inhibitor in the Ge1Sb4Te5 film surface CMP slurry could achieve an almost recess-free Ge1Sb4Te5 film surface of the confined-PCRAM cells, having an aspect ratio of 60-nm-height to 4-nm-diameter after CMP.

In this study, the chemical decomposition of a polyimide-film (i.e., a PI-film)-surface into a soft-film-surface containing negatively charged pyromellitic dianhydride (PMDA) and neutral 4,4′-oxydianiline (ODA) was successfully performed. The chemical decomposition was conducted by designing the slurry containing 350 nm colloidal silica abrasive and small molecules with amine functional groups (i.e., ethylenediamine: EDA) for chemical–mechanical planarization (CMP). This chemical decomposition was performed through two types of hydrolysis reactions, that is, a hydrolysis reaction between OH− ions or R-NH3+ (i.e., EDA with a positively charged amine groups) and oxygen atoms covalently bonded with pyromellitimide on the PI-film-surface. In particular, the degree of slurry adsorption of the PI-film-surface was determined by the EDA concentration in the slurry because of the presence of R-NH3+, that is, a higher EDA concentration resulted in a higher degree of slurry adsorption. In addition, during CMP, the chemical decomposition degree of the PI-film-surface was principally determined by the EDA concentration; that is, the degree of chemical composition was increased noticeably and linearly with the EDA concentration. Thus, the polishing-rate of the PI-film-surface increased notably with the EDA concentration in the CMP slurry.

Corresponding to the principles of biological synapses, an essential prerequisite for hardware neural networks using electronics devices is the continuous regulation of conductance. We implemented artificial synaptic characteristics in a (GeTe/Sb2Te3)16 iPCM with a superlattice structure under optimized identical pulse trains. By atomically controlling the Ge switch in the phase transition that appears in the GeTe/Sb2Te3 superlattice structure, multiple conductance states were implemented by applying the appropriate electrical pulses. Furthermore, we found that the bidirectional switching behavior of a (GeTe/Sb2Te3)16 iPCM can achieve a desired resistance level by using the pulse width. Therefore, we fabricated a Ge2Sb2Te5 PCM and designed a pulse scheme, which was based on the phase transition mechanism, to compare to the (GeTe/Sb2Te3)16 iPCM. We also designed an identical pulse scheme that implements both linear and symmetrical LTP and LTD, based on the iPCM mechanism. As a result, the (GeTe/Sb2Te3)16 iPCM showed relatively excellent synaptic characteristics by implementing a gradual conductance modulation, a nonlinearity value of 0.32, and 40 LTP/LTD conductance states by using identical pulse trains. Our results demonstrate the general applicability of the artificial synaptic device for potential use in neuro-inspired computing and next-generation, non-volatile memory.

Air pollution contains sulfur dioxide (SO2) of 31.1%, nitrogen dioxide (NO2) of 27.2%, carbon oxide (COx) of 16.8%, and mineral particles of 6.3% according to the ministry of environment, Korea. Since air pollution has been harmfully affecting the health of people, the importance of controlling gas concentration and air pollution have been increased greatly and socially. To measure those gases the conventional gas detectors used by ultraviolet (UV) absorption method cannot display the image for total distribution of the gas and use public in daily life. In addition, the gas detectors used mainly at coal-fired power plant are installed in the chimney and a length of detecting probe in a detector is about 1 to 2 meters, which analyze quantitatively the gas passing through the hole with a diameter of 5-10 cm. Furthermore, since the conventional gas detectors measure only a small amount of gas coming out from chimney and their accuracies are not precise, thus, the more precise method is required for measuring the emitted gas quantitatively. In this study, therefore, we propose ultraviolet CMOS image sensor (UV-CIS) which can detect NO2 and SO2 gases quantitatively to enhance the sensitivity in detecting such gases. In particular, we investigated the characteristics of UV-CIS. We fabricated the UV-CIS embedded with blue-light emitting QD films. The structure of the UV-CIS consists of blue QDs film and blue color filter placed on conventional Si-CIS. The fabricated UV-CIS demonstrated much higher sensitivity in detecting both NO2 and SO2 gases at whole range of concentrations than conventional CIS. In particular, the sensitivity of the UV-CIS increased 1.9 times higher in detecting NO2 and 9.4 times higher in detecting SO2 than conventional CIS, respectively. It was conformed that the QD film converted UV into visible light through energy-down-conversion mechanism, which led to enhancing a sensitivity to UV light in CIS. Finally, we present energy-down-conversion characteristics of QDs synthesized, UV absorption characteristics of NO2 and SO2 gases, and the mechanism on sensing UV-light of UV-CIS to analyze an air environment.

Abstract Spiking neurons communicate with other neurons using sparse and binary signals in a human brain, so they can achieve real-time processing of the information with ultra-low power consumption[1,2]. Thereby, spiking neurons are essential elements for building an energy-efficient biomimetic spatiotemporal system. Recently, to emulate the behavior of biological neuron, many researches for memristive device-based neurons with peripheral circuits (i.e., sense-amplifier or reset circuit)[3] and complementary metal-oxide-semiconductor (CMOS) neurons with capacitors have been reported[4]. Most of the reported memristive device-based neurons required a high operation voltage (>1.2 V) for emulating integrate function of a biological neuron. In addition, complementary metal-oxide-semiconductor-based neurons could not achieve high neuronal density due to using a capacitor in emulating integrate function. In this study, therefore, we propose an electrochemical metallization cell based memristive neuron chip fabricated with 28-nm CMOS process having a low operation voltage ( Acknowledgement This research was supported by National R&D Program through the National Research Foundation of Korea(NRF) funded by Ministry of Science and ICT(2021M3F3A2A01037733). Reference Mead, C. Neuromorphic Electronic Systems. Encycl. Comput. Neurosci. 78, 1979–1979 (2015). Douglas, R. Neuromorphic Analogue VLSI. Annu. Rev. Neurosci. 18, 255–281 (1995). Tuma, T., Pantazi, A., Le Gallo, M., Sebastian, A. & Eleftheriou, E. Stochastic phase-change neurons. Nat. Nanotechnol. 11, 693–699 (2016). Aamir, S. A., Müller, P., Hartel, A., Schemmel, J. & Meier, K. A highly tunable 65-nm CMOS LIF neuron for a large scale neuromorphic system. Eur. Solid-State Circuits Conf. 2016-Octob, 71–74 (2016). Figure 1

Localized-surface plasmon resonance (LSPR) of nanoscale particles (NPs) has been widely used for the enhancement of light-harvesting capability and current density in solar cells. Here, the LSPR was modulated through selective plasmon nanocrystals (NCs) with tuning the morphology (size and interparticle-spacing) using thermal evaporation. The selective NCs were implemented between the hole-transport layer and front anode contact in polymer solar cells (PSCs) to dramatically improve the short-circuit-current density and power-conversion efficiency by + 31.04 and + 32.02%, respectively. The photovoltaic enhancements were reflected by the significant increase in external quantum efficiency (+ 38%) and a decrease in optical losses (− 26%). Such promising results, together with the simple, controllable, and scalable preparation method, can pave the way for highly efficient plasmonic PSCs.

A novel perpendicular spin-transfer torque magnetic random-access memory spin valve with a memory-cell size below 20 nm × 20 nm and a thermal stability factor Δ of ~77 (10-year retention time) was designed by ferromagnetically coupling a multiple free layer [Co/Pt]n to Co 2 Fe 6 B 2 having interfacial perpendicular magnetic anisotropy (i-PMA) instead of coupling to a conventional double i-PMA free layer (Δ = 33). Thermal stability (Δ) increased with an increase of n in the [Co(0.47nm)/Pt(0.23 nm)]n multiple free layer. In particular, Δ = 80 could be achieved with n = 4 for a 15 nm × 15 nm memory-cell size. However, the tunneling magnetoresistance (TMR) ratio, which should be above 150% to assure a reasonable sensing margin, rapidly decreased from 190% to 98% with an increase in n from 0 to 4. This decrease was associated with W and Pt atomic diffusion into the MgO tunneling barrier. Improvement in the crystallinity of the MgO tunneling barrier increased the TMR ratio to 144% for n = 4.

The n

Magnetic tunneling junction (MTJ) materials such as CoFeB, Co, Pt, MgO, and the hard mask material such as W and TiN were etched with a reactive ion beam etching (RIBE) system using H

A perpendicular spin transfer torque (p-STT)-based neuron was developed for a spiking neural network (SNN). It demonstrated the integration behavior of a typical neuron in an SNN; in particular, the integration behavior corresponding to magnetic resistance change gradually increased with the input spike number. This behavior occurred when the spin electron directions between double Co2Fe6B2 free and pinned layers in the p-STT-based neuron were switched from parallel to antiparallel states. In addition, a neuron circuit for integrate-and-fire operation was proposed. Finally, pattern-recognition simulation was performed for a single-layer SNN.

For applications as high-brightness light-emitting-diodes, a bow-free freestanding gallium nitride (GaN) wafer 2 inch in diameter and ∼185 μm in thickness was fabricated by process-designing pit and mirror GaN layers grown via hydride-vapor-phase epitaxy, laser lift-off, N-face polishing of the pit GaN layer, and three-step polishing of the mirror GaN layer using 3.0 μm-, 0.5 μm-, and 50 nm-diameter diamond abrasives and by inductively-coupled-plasma reactive-ion etching. The considerably large concave shape of the GaN wafer could be decreased by controlling the removal amount of the Ga-face mirror layer during the first step of the polishing process, which approached a bow-free shape or changed with further polishing; this well correlated with the residual stress of the polished GaN wafer.

We present a novel quantum dot enhancement film (QDEF) with a remarkable RGB color gamut of over 100.4% (134.2%) of the Rec. 2020 standard (NTSC standard), respectively for a high-resolution liquid-crystal display (LCD). Our efficient QDEF was fabricated by using a highly transparent resin incorporated with high photoluminesce-quantum yield (PL-QY) and narrow full width at half maximum CsPbBr1I2 QDs (Pr-QDs) and CdSe/ZnS QDs (Cd-QDs). The proposed PrCd-QDEF in a LCD with color filters rendered a blue photoluminesce (PL) peak at 452 nm with a FWHM of 20.4 nm, a green PL peak at 530.1 nm with a FWHM of 23.8 nm, and a red color peak at 652.4 nm with a FWHM of 28.1 nm. Moreover, The PrCd-QDEF did not show any cross-talk between the RGB PL colors. Such promising optical results, along with the simple and cost-effective preparation technique, might encourage the manufacture of super high resolution LCDs using a PrCd-QDEF.

The Conductive-bridge random-access memory (CBRAM) cell is a promising candidate for a terabit-level non-volatile memory due to its remarkable advantages. We present for the first time TiN as a diffusion barrier in CBRAM cells for enhancing their reliability. CuO solid-electrolyte-based CBRAM cells implemented with a 0.1-nm TiN liner demonstrated better non-volatile memory characteristics such as ~ 106 AC write/erase endurance cycles with 100-μs AC pulse width and a long retention time of ~ 7.4-years at 85 °C. In addition, the analysis of Ag diffusion in the CBRAM cell suggests that the morphology of the Ag filaments in the electrolyte can be effectively controlled by tuning the thickness of the TiN liner. These promising results pave the way for faster commercialization of terabit-level non-volatile memories.

Lead trihalide perovskite nanomaterials are widely studied due to their remarkable optoelectronic properties. Despite their outstanding and demonstrated potential, these materials have been kept from practical application due to their crippling instability in ambient conditions. From electron microscopy studies of this series of quantum dots (QDs) we demonstrate that the onset of degradation in optical properties coincides with the appearance of nano black spots (NBSs) on the QDs. Elemental mapping using electron microscopy revealed the NBSs to be areas with higher concentration of lead. We have looked at the possible mechanisms to explain NBSs and found that they may arise due to two very different pathways. The first one is due to crystal growth initiated by excess reactants and the second is due to chemical degradation of the QD surface. Further we have invoked the well known geometrical stability criterion for perovskites, Goldschmidt's tolerance factor to predict the appearance of NBSs and the onset of optical instability of CsPbBr3−xIx QDs. This correlation can be used as a criterion to aid the selection of more optically stable perovskite QDs for practical applications.

In a two-terminal-electrode vertical thyristor, the latch-up and latch-down voltages are decreased when the memory operation temperature of the memory cells increases, resulting in a severe reliability issue (i.e. thermal instability). This study fundamentally solves the thermal instability of a vertical-thyristor by achieving a cross-point memory-cell array using a vertical-thyristor with a structure of vertical n++-emitter, p+-base, n+-base, and p++-emitter. The vertical-thyristor using a Schottky contact metal emitter instead of an n++-Si emitter significantly improves the thermal stability between 293 K and 373 K. Particularly, the improvement degree of the thermal stability is increased significantly with the use of the Schottky contact metal work function. Because the thermal instability (i.e. degree of latch-up voltage decrement vs. memory operation temperature) decreases with an increase in the Schottky contact metal work function, the dependency of the forward current density between the Schottky contact metal and p+-Si based on the memory operation temperature reduces with increase in the Schottky contact metal work function. Consequently, a higher Schottky contact metal work function produces a higher degree of improvement in the thermal stability, i.e. W (4.50 eV), Ti (4.33 eV), Ta (4.25 eV), and Al (4.12 eV). Further research on the fabrication process of a Schottky contact metal emitter vertical-thyristor is essential for the fabrication of a 3D cross-point memory-cell.