Search

Plasma-enhanced atomic layer deposition (ALD) is a common method for fabricating Hf0.5Zr0.5O2 (HZO) ferroelectric thin films that can be performed using direct-plasma (DP) and remote-plasma (RP) methods. This study proposed co-plasma ALD (CPALD), where DPALD and RPALD are applied simultaneously. HZO films fabricated using this method showed wake-up-free polarization properties, no anti-ferroelectricity, and high fatigue endurance when DPALD and RPALD started simultaneously. To minimize defects in the film that could negatively affect the low polarization properties and fatigue endurance, the direct plasma power was reduced to 75 W. Thus, excellent fatigue endurance for at least 109 cycles was obtained under a high total remanent polarization of 47.3 μC/cm2 and an applied voltage of 2.5 V. X-ray photoelectron spectroscopy and transmission electron microscopy were used to investigate the mechanisms responsible for these properties. The HZO films fabricated by CPALD contained few lattice defects (such as nonstoichiometric hafnium, nonlattice oxygen, and residual carbon) and no paraelectric phase (m-phase). This was attributed to the low-carbon residuals in the film, as high-energy activated radicals were supplied by the adsorbed precursors during film formation. This facilitated a smooth transition to the o-phase during heat treatment, which possessed ferroelectric properties.

We aimed to fabricate reliable memory devices using HfO2, which is gaining attention as a charge-trapping layer material for next-generation NAND flash memory. To this end, a new atomic layer deposition process using sequential remote plasma (RP) and direct plasma (DP) was designed to create charge-trapping memory devices. Subsequently, the operational characteristics of the devices were analyzed based on the thickness ratio of thin films deposited using the sequential RP and DP processes. As the thickness of the initially RP-deposited thin film increased, the memory window and retention also increased, while the interface defect density and leakage current decreased. When the thickness of the RP-deposited thin film was 7 nm, a maximum memory window of 10.1 V was achieved at an operating voltage of ±10 V, and the interface trap density (Dit) reached a minimum value of 1.0 × 1012 eV−1cm−2. Once the RP-deposited thin film reaches a certain thickness, the ion bombardment effect from DP on the substrate is expected to decrease, improving the Si/SiO2/HfO2 interface and thereby enhancing device endurance and reliability. This study confirmed that the proposed sequential RP and DP deposition processes could resolve issues related to unstable interface layers, improve device performance, and enhance process throughput.

In this study, 18 strains of cyanobacteria were isolated from seven sites, including the Han River and Anseong Stream in Republic of Korea, and we propose these isolated strains as Limnonema gen. nov., belonging to the Aerosakkonemataceae family of the Oscillatoriales order, and also, as L. hangangris sp. nov. and L. anseonga sp. nov. These strains were identified based on morphological data using a light microscope and a transmission electron microscope, and molecular data using 16S rRNA and 16S–23S ITS gene sequences. The genus Limnonema was mainly collected as planktons, and some L. hangangris (ACKU-695–697) appeared as epilithic cyanobacteria. The genus Limnonema showed filamentous trichomes, intracellular gas vacuoles, and irregular thylakoids arrangement, which was distinct from genera Cephalothrix, Microseira, and Potamosiphon belonging to the family Aerosakkonemataceae. Moreover, the cell widths of genus Limnonema were narrower than those of genus Aerosakkonema, which is the type genus of the family Aerosakkonemataceae, and L. anseonga contained more cells with wider widths than those of L. hangangris. In the 16S rRNA gene sequence phylogeny, genus Limnonema belonged to the family Aerosakkonemataceae and was distinguished from its close relatives, genera Aerosakkonema and Cephalothrix, and L. hangangris and L. anseonga formed different branches. In 16S rRNA gene sequence similarity, genus Limnonema showed 95.4–95.9% and 93.6–94.4% similarity with genera Aerosakkonema and Cephalothrix, respectively, and L. hangangris and L. anseonga showed 97.6–97.7% similarity between each other. In the 16S–23S ITS secondary structure, the D1–D1′, Box-B, and V3 helices of genus Limnonema were distinguished from genera belonging to the family Aerosakkonemataceae, and the V3 helices of L. hangangris and L. anseonga were also different from each other.

Optimization of equipment structure and process conditions is essential to obtain thin films with the required properties, such as film thickness, trapped charge density, leakage current, and memory characteristics, that ensure reliability of the corresponding device. In this study, we fabricated metal–insulator–semiconductor (MIS) structure capacitors using HfO2 thin films separately deposited by remote plasma (RP) atomic layer deposition (ALD) and direct-plasma (DP) ALD and determined the optimal process temperature by measuring the leakage current and breakdown strength as functions of process temperature. Additionally, we analyzed the effects of the plasma application method on the charge trapping properties of HfO2 thin films and properties of the interface between Si and HfO2. Subsequently, we synthesized charge-trapping memory (CTM) devices utilizing the deposited thin films as charge-trapping layers (CTLs) and evaluated their memory properties. The results indicated excellent memory window characteristics of the RP-HfO2 MIS capacitors compared to those of the DP-HfO2 MIS capacitors. Moreover, the memory characteristics of the RP-HfO2 CTM devices were outstanding as compared to those of the DP-HfO2 CTM devices. In conclusion, the methodology proposed herein can be useful for future implementations of multiple levels of charge-storage nonvolatile memories or synaptic devices that require many states.

The aim of this study was to examine genetic variations underlying the early neurodevelopmental outcome of developmental disabilities (DDs). The study cohort consisted of 191 children with DDs. Diagnosis was assessed at baseline and at the index age (72-84 months). Exome sequencing was conducted and putative risk variants were identified. According to the diagnostic improvement, children were categorized into the improvement group (n = 19) and the non-improvement group (n = 172). Compared to the non-improvement group, the improvement group had lower number of risk variants in known DD genes and haploinsufficient genes, and lower number of overall putative risk variants. Our results may serve as a preliminary basis for developing a model that informs clinical outcome by sequencing analysis.

Piezoelectric material properties were optimized to develop materials for an ultrasonic vibrator targeting a high vibration efficiency. Herein, novel materials were developed using a composition represented by 0.08Pb(Ni1/3Nb2/3)O3-0.07Pb(Mn1/3Nb2/3)O3-0.85Pb(Zr0.5Ti0.5)O3 + 0.3 wt.% CuO + 0.3 wt.% Fe2O3 with 0.3 wt.% Sb2O3 doping. A ceramic shape with a thickness of 2 mm was optimized using finite element analysis software, and high values of coupling factors (0.54) and mechanical quality factors (1151) were obtained. This ceramic was used to fabricate a bio-beauty device (frequency = 1 MHz), and the manufactured ultrasonic vibrator indicated that the actuator oscillated with the maximum amplitude at a frequency of 1.06 MHz.

In this study, the influence of socio-cultural factors on attitudes toward artificial intelligence (AI) was investigated. In total, 1,677 Korean middle school students were selected to participate, and a test tool was used to measure the attitude toward AI. As a result, according to socio-cultural factors, middle school students' attitudes toward AI were affected differently by gender- or AI-related experiences. In particular, students experiencing difficulties because of socio-cultural factors showed a more positive attitude toward AI if they had an AI education. On the other hand, interest toward AI and programming experience had a significant effect on attitudes toward AI and was not affected by socio-cultural factors. In particular, students with high interest toward AI or experience with block- and text-based programming languages showed significantly positive attitudes toward AI. Hence, the disparity in middle school students' attitude toward AI according to socio-cultural factors was found.

Purpose: To investigate the effect of BruxZir Steel treatment on the fracture resistance of zirconia threeunit bridges prepared using 5Y-PSZ-based zirconia blanks. Materials and Methods: Three-unit zirconia bridges were milled using CAD/CAM from homogeneous bisque zirconia blanks (5Y-PSZ-based) supplied by various manufacturers and sintered. Fracture resistance was analyzed with dynamic loading. For each zirconia blank, the fracture resistance of the sintered test restoration (cementation surface treated with BruxZir Steel) was compared to the sintered control restoration (untreated cementation surface). Finite element analysis (FEA) was used to analyze the stress distribution on the three-unit bridge under an axial load. Results: The fracture resistance of the test restorations was significantly higher than that of the control restorations for all manufacturers considered in this study (P < .05). Furthermore, the restoration made of BruxZir Esthetic treated with BruxZir Steel had the highest fracture resistance compared to the other restorations. In addition, the three-unit bridge restorations prepared from 5Y-PSZ-based zirconia blanks exhibited differences in grain size and fracture toughness depending on the presence or absence of BruxZir Steel treatment. The locations of high stresses under FEA correlated well with the fracture locations in the corresponding experimental test. FEA also demonstrated the improved performance of the BruxZir Steel-treated sample compared to the control. Conclusions: The fracture resistance of 5Y-PSZ-based BruxZir Steel-treated three-unit bridges was significantly higher (min = 30%, max = 198%) than the control. [ABSTRACT FROM AUTHOR]