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Accomplishments of enhanced activity and durability are a major concern in the design of catalysts for acidic water oxidation. To date, most studied supported metal catalysts undergo fast degradation in strongly acidic and oxidative environments due to improper controlling of the interface stability caused by their lattice mismatches. Here, we evaluate the activity–stability trends of in situ crystallized antimony-doped tin oxide (Sb-SnO2)@RuOx (Sb-SnO2@RuOx) heterostructure nanosheets (NSs) for acidic water oxidation. The catalyst prepared by atomic layer deposition of a conformal Ru film on antimony-doped tin sulfide (Sb-SnS2) NSs followed by heat treatment highlights comparable activity but longer stability than that of the ex situ catalyst (where Ru was deposited on Sb-SnO2 followed by heating). Air calcination for in situ crystallization allows the formation of hierarchical mesoporous Sb-SnO2 NSs from as-prepared Sb-SnS2 NSs and parallel in situ transformation from Ru to RuOx, resulting in a compact heterostructure. The significance of this approach significantly resists corrosive dissolution, which is justified by the enhanced oxygen evolution reaction (OER) stability of the catalyst compared to most of the state-of-the-art ruthenium-based catalysts including Carbon@RuOx (which shows ∼10 times higher dissolution) as well as Sb-SnO2@Com. RuOx and Com. RuO2. This study demonstrates the controlled interface stability of heterostructure catalysts toward enhancing OER activity and stability., full_html

The microstructure and properties of WTi alloy films with 0~23 at.% Ti prepared by magnetron sputtering were investigated. The electrical resistivity gradually increased with the increase in the Ti content. When the Ti content was 6.8 at.%, the temperature coefficient of resistance of the alloy film reached the maximum value of 19.5 × 10−4 K−1, which is 3.6 times higher than that of the pure W film. After several thermal resistance tests, the temperature coefficient of resistance of the WTi alloy film with 6.8 at.% Ti decreased gradually. After five measurements, the temperature coefficient of resistance decreased gradually from 19.5 × 10−4 to 16.3 × 10−4 K−1. After annealing at 500 °C for 30 min, the grain size of the WTi alloy film (6.8 at.% Ti) increased, a few pores appeared, and the density of the film decreased. The temperature coefficient of resistance decreased from 19.5 × 10−4 K−1 to 14 × 10−4 K−1. When the annealing time was increased to 60 min, the structure and properties of the WTi alloy film remained basically unchanged. After conducting the annealing treatment for 30 min, the WTi films showed excellent stability in the thermal resistance tests, and their temperature coefficient of resistance was basically consistent after cyclic thermal loading, which has promising application prospects for the temperature measurement of tools and dies.

Yttria-stabilized zirconia (YSZ) nanospheres were synthesized by calcination at 900 °C after the adsorption of Y3+ ions into the pores of a zirconium-based metal–organic framework (MOF). The synthesized 3YSZ (zirconia doped with 3 mol% Y2O3), 8YSZ (8 mol% Y2O3), and 30YSZ (30 mol% Y2O3) nanospheres were found to exhibit uniform sizes and shapes. Complex permittivity and complex permeability were carried out in K-band (i.e., 18–26.5 GHz) to determine their suitability for use as low-k materials in 5G communications. The real and imaginary parts of the permittivity of the sintered 3YSZ were determined to be 21.24 and 0.12, respectively, while those of 8YSZ were 22.80 and 0.16, and those of 30YSZ were 7.16 and 0.38. Control of the real part of the permittivity in the sintered YSZ was facilitated by modifying the Y2O3 content, thereby rendering this material an electronic ceramic with potential for use in high-frequency 5G communications due to its excellent mechanical properties, high chemical resistance, and good thermal stability. In particular, it could be employed as an exterior material for electronic communication products requiring the minimization of information loss.

To fabricate high efficiency photoanodes for water oxidation, it is highly required to engineer their nanoporous architecture and interface to improve the charge separation and transport efficiency...

Low-temperature fuel cells have attracted significant attention owing to their low cost and high performance. Herein, uniform Ru nanoparticles (NPs) with various size distributions were synthesized as a non-Pt catalyst on a carbon support by fluidized bed reactor-atomic layer deposition (FBR-ALD) as a function of ALD cycles for the hydrogen oxidation reaction (HOR) in alkaline medium. With an increase in the number of ALD cycles from 5 to 30 cycles, the wt% of the Ru NPs increased from ∼5 to ∼32 wt%. In addition, the structural characterization of the Ru NPs revealed the formation of Ru NPs with a uniform, dense, and controllable size (∼2–4 nm) and crystallinity depending on the growth cycle of ALD. However, the 10 cycled Ru catalyst with a NP size of ∼2 nm possessed a highly electrochemically active roughened surface (amorphous moiety covered the crystallite), which enhanced its HOR and mass activity. Remarkably, the ALD-synthesized Ru catalyst outperformed a commercial Ru/C catalyst with a similar wt%. Hydrogen binding energy (HBE) calculations revealed that the specific activity of the catalyst increased with decreasing HBE. The mechanistic pathway for the HOR indeed illustrates that enhanced activity under alkaline conditions was found owing to the weakening of the metal–H interaction influenced by the Ru NP crystallinity and size. The findings of this study indicate that the FBR-ALD technique is an effective, scalable approach for the synthesis of active non-Pt metal catalysts.

Extended and oriented rutile nanowires (NWs) hold great promise for numerous applications because of their various tunable physicochemical properties in air and/or solution media, but their direct synthesis on a wide range of conducting substrates remains a significant challenge. Their device performance is governed by relevant NW geometries that cannot be fully controlled to date by varying bulk synthetic conditions. Herein, orientation engineering of rutile SnO2 NWs on a variety of conducting substrates by atomic layer deposition (ALD) seeding has been investigated. The seeded growth controls the nucleation event of the NW, and thicknesses and crystallographic properties of seed layers are the key parameters toward tuning the NW characteristics. The seed layers on carbon cloth produce NWs with highly enhanced electrochemically active surface area, which would show efficient electrochemical CO2 reduction. In addition, the hierarchical architecture resulted from the seeded growth of NWs on SnO2 nanosheets allows thin layers of BiVO4, forming a heterojunction photoanode, which shows a record charge separation efficiency of 96.6% and a charge-transfer efficiency of 90.2% at 1.23 V versus the reversible hydrogen electrode among, to date, the reported BiVO4-based photoanodes for water oxidation. Our study illustrates that such a versatile interfacial engineering effort by the ALD technique would be promising for further wide range of practical applications.

In recent years, there has been growing interest in porous ceramics in many research areas given their superior thermal and chemical resistance capabilities, unlike porous metals and porous polymers. Among the various types of porous ceramics, reticulated porous ceramics can offer significant industrial potential due to the low density and high permeability of these materials. However, industrial applications are somewhat rare owing to the rather low compressive strength of reticulated porous ceramics compared to other types of porous ceramics. Although there have been many studies related to reticulated porous ceramics, few have focused on reticulated porous zirconia. Therefore, the aim of this study is to determine how to obtain a high compressive strength in reticulated porous zirconia by optimizing the process conditions of the solid loading level and the particle size and by using additives in a zirconia slurry sample. Furthermore, the authors assess the effects on the microstructure and compressive strength of multiple slurry coating, specifically from one to three. In conclusion, the effect of varying these various process conditions on the resulting improvement in compression strength was investigated, and the compression strength of reticulated porous zirconia was significantly increased from 0.14 to 9.43 MPa. The characteristics investigated include the pore characteristics (pore density, pore size and pore structure), the sintering behavior (linear shrinkage), the mechanical properties (compressive strength), and the dielectric properties (dielectric breakdown strength).

Seawater splitting represents an inexpensive and attractive route for producing hydrogen, which does not require a desalination process. Highly active and durable electrocatalysts are required to sustain seawater splitting. Herein we report the phosphidation-based synthesis of a cobalt–iron–phosphate ((Co,Fe)PO4) electrocatalyst for hydrogen evolution reaction (HER) toward alkaline seawater splitting. (Co,Fe)PO4 demonstrates high HER activity and durability in alkaline natural seawater (1 M KOH + seawater), delivering a current density of 10 mA/cm2 at an overpotential of 137 mV. Furthermore, the measured potential of the electrocatalyst ((Co,Fe)PO4) at a constant current density of −100 mA/cm2 remains very stable without noticeable degradation for 72 h during the continuous operation in alkaline natural seawater, demonstrating its suitability for seawater applications. Furthermore, an alkaline seawater electrolyzer employing the non-precious-metal catalysts demonstrates better performance (1.625 V at 10 mA/cm2) than one employing precious metal ones (1.653 V at 10 mA/cm2). The non-precious-metal-based alkaline seawater electrolyzer exhibits a high solar-to-hydrogen (STH) efficiency (12.8%) in a commercial silicon solar cell.

The specific capacitance and energy density of antimony trisulfide (Sb2S3)@carbon supercapacitors (SCs) have been limited and are in need of significant improvement. In this work, Sb2S3 nanoparticl...

Rutile-TiO2 thin films have potential for use in high-k applications, such as dynamic random-access memory capacitors; however, they are difficult to realize without using noble-metal-based oxide substrates. Therefore, we proposed a new approach for the preparation of rutile TiO2 by a small amount of Sn doping and the insertion of ultra-thin SnO2 to achieve enhanced dielectric performance without using noble-metal-based electrodes. It was confirmed that the crystallinity of rutile TiO2 was remarkably enhanced in Sn-doped TiO2 formed on an ultra-thin SnO2 interlayer. Moreover, 10 nm-thick Sn-doped TiO2 thin film on a 1-nm SnO2 interlayer exhibited a high dielectric constant of about 80.

Bismuth telluride (Bi2Te3) has recently attracted significant attention owing to its unique physical properties as a three-dimensional topological insulator and excellent properties as a thermoelectric material. Meanwhile, it is important to develop a synthesis process yielding high-quality single crystals over a large area to study the inherent physical properties and device applications of two-dimensional materials. However, the maturity of Bi2Te3 vapor-phase synthesis is not good, compared to those of other semiconductor two-dimensional crystals. In this study, therefore, we report the synthesis of relatively large-area Bi2Te3 crystals by vapor transport method, and we investigated the key process parameters for a synthesis of relatively thin and large-area Bi2Te3 crystals. The most important factor determining the crystal synthesis was the temperature of the substrate. A Bi2Te3 device exhibited a considerable photocurrent when the laser was irradiated inside the electrode area. This indicated that the...

The self-assembly of block copolymers (BCPs) has attracted considerable attention because it can effectively generate highly ordered nanostructures through a simple and cost-effective process. However, in BCP annealing systems, there remain several challenges and issues that must be resolved to achieve more rapid and tunable pattern formation of BCPs with a high Flory–Huggins parameter (χ) for next-generation lithography applications. Here, we introduce a useful annealing technique to induce a rapid morphological transition of sphere-forming poly(styrene-b-dimethylsiloxane) (PS-b-PDMS) BCPs by employing multistep solvent vapor annealing (MSVA) and a combined annealing process of solvent vapor annealing (SVA) and immersion annealing (IA). We successfully obtained well-ordered sub-20 nm line, dot, core–shell dot, and core–shell line structures with a short annealing time (

Uniform, well-ordered sub-20 nm patterns can be generated by the templated self-assembly of block copolymers (BCPs) with a high Flory-Huggins interaction parameter (χ). However, the self-assembled BCP monolayers remain limited in the possible structural geometries. Here, we introduce a multiple self-assembly method which uses di-BCPs to produce diverse morphologies, such as dot, dot-in-honeycomb, line-on-dot, double-dot, pondering, dot-in-pondering, and line-on-pondering patterns. To improve the diversity of BCP morphological structures, we employed sphere-forming and cylinder-forming poly(styrene-block-dimethylsiloxane) (PS-b-PDMS) BCPs with a high χ. The self-assembled mono-layer and double-layer SiOx dot patterns were modified at a high temperature (∼800 °C), showing hexagonally arranged (dot) and double-hexagonally arranged (pondering) SiOx patterns, respectively. We successfully obtained additional new nanostructures (big-dot, dot-in-honeycomb, line-on-dot, pondering, dot-in-pondering, and line-on-pondering types) through a second self-assembly of cylinder-forming BCPs using the dot and pondering patterns as guiding templates. This simple approach can likely be extended to the multiple self-assembly of many other BCPs with good functionality, significantly contributing to the development of various nanodevices.

Recently, porous ceramics have received much attention from researchers because of their excellent thermal and chemical stabilities compared to their counterparts (such as porous polymers and metals), despite their inferior mechanical instability. Among the various types of porous ceramics, reticulated porous ceramics have significant industrial potential because of their synergistic high porosity and permeability. However, to the best of our knowledge, there is insufficient data on the processing conditions or preparing optimal reticulated porous alumina. Therefore, we prepared and characterized reticulated porous alumina specimens by controlling various processing conditions, namely average particle size, solid loading, binder, and dispersant. The data obtained were used to assess whether the compressive strength of the reticulated porous alumina could be enhanced and to discuss the potential of these materials for various applications.

Nanostructuring is considered one of the key approaches to achieve highly efficient thermoelectric alloys by reducing thermal conductivity. In this study, we investigated the effect of oxide (ZnO and SnO2) nanolayers at the grain boundaries of polycrystalline In0.2Yb0.1Co4Sb12 skutterudites on their electrical and thermal transport properties. Skutterudite powders with oxide nanolayers were prepared by atomic layer deposition method, and the number of deposition cycles was varied to control the coating thickness. The coated powders were consolidated by spark plasma sintering. With increasing number of deposition cycle, the electrical conductivity gradually decreased, while the Seebeck coefficient changed insignificantly, this indicates that the carrier mobility decreased due to the oxide nanolayers. In contrast, the lattice thermal conductivity increased with an increase in the number of deposition cycles, demonstrating the reduction in phonon scattering by grain boundaries owing to the oxide nanolayers. Thus, we could easily control the thermoelectric properties of skutterudite materials through adjusting the oxide nanolayer by atomic layer deposition method.

The performance of proton exchange membrane fuel cells (PEMFCs) depends on the controlled size, dispersion and density of Pt nanoparticles (NPs) on carbon supports, which are strongly affected by the carbon characteristics and fabrication methods. Here, we demonstrated a high-performance Pt/carbon catalyst for PEMFCs using fluidized bed reactor atomic layer deposition (FBR-ALD) that was realized by an effective matching of the carbon supports for the FBR-ALD process and an optimization of the ionomer content during the preparation of the membrane electrode assembly (MEA). For this, the synthesis of Pt NPs was conducted on two porous supports (Vulcan XC-72R and functionalized carbon) by FBR-ALD. The functionalized carbon possessed a higher surface area with a large pore volume, abundant defects in a disordered structure and a large number of oxygen functional groups compared to those of the well-known Vulcan carbon. The favorable surface characteristics of the functionalized carbon for nucleation produced Pt particles with an increased uniformity and density and a narrow size range, which led to a higher electrochemical surface area (ECSA) than that of Pt/Vulcan carbon and commercial Pt/carbon. The PEMFC test of the respective Pt/carbon samples was investigated, and highly dense and uniform Pt/functionalized-carbon showed the highest performance through optimization of the higher ionomer content compared to that for the ALD Pt growth on Vulcan carbon and commercial Pt/carbon. In addition, the Pt catalyst using ALD demonstrated a significant long-term stability for the PEMFC. This finding demonstrates the remarkable advantages of FBR-ALD for the fabrication of Pt/carbon and the ability of functionalized carbon supports to achieve a high PEMFC efficiency and an enhanced durability. Small tweaks to techniques used to manufacture platinum catalysts can have a big impact on the long-term stability of fuel cells. Platinum nanoparticle catalysts help fuel cells turn hydrogen and oxygen into water and electricity, but their small size makes them tricky to manipulate. Se-Hun Kwon from Pusan National University in Busan, South Korea, and colleagues have now optimized a high-tech procedure for attaching these tiny nanocatalysts to large, porous materials known as carbon supports. Their process coats various supports with platinum nanoparticles, less than one monolayer at a time, until the desired thicknesses are reached. Various factors including the physical textures of the supports and leftover chemical impurities were shown to significantly affect coating uniformity. Adjusting these factors enabled the team to generate supports with greater durability than commercial platinum–carbon composites. Very efficient, fast and scalable Fluidized Bed Reactor Atomic Layer Deposition (FBR-ALD) of highly dense and uniform Pt nanoparticles (NPs) on the functionalized carbon were successfully demonstrated for the proton exchange membrane fuel cell (PEMFC) application. The textural properties, functional groups and structural defects of the carbon supports significantly influenced Pt NPs deposition. A proper carbon supporter matching for FBR-ALD of Pt resulted in excellent electrochemical properties, long-term durability and fuel cell performance.

A method for significantly increasing the growth rates (GRs) of high- k oxide thin films grown via plasma-enhanced atomic layer deposition (PE-ALD) by enhancing the plasma density through the addition of Ar gas to the O2 plasma oxidant was developed. This approach led to improvements of ∼60% in the saturation GRs of PE-ALD ZrO2, HfO2, and SiO2. Furthermore, despite the significantly higher GR enabled by PE-ALD, the mechanical and dielectric properties of the PE-ALD oxide films were similar or even superior to those of films grown via the conventional O2 plasma process. Optical emission spectroscopy analyses in conjunction with theoretical calculation of the electron energy distribution function revealed that adding Ar gas to the O2 plasma increased the density of high-energy electrons, thereby generating more O2 plasma species, such as ions and radicals, which played a key role in improving the GRs and the properties of the films. This promising approach is expected to facilitate the high-volume manufacturing of films via PE-ALD, especially for use as gate insulators in thin-film transistor-based devices in the display industry.

This research was mainly supported by the Global Frontier R&D Program (2013M3A6B1078874) on Center for Hybrid Interface Materials (HIM) funded by the Ministry of Science, ICT & Future Planning, Republic of Korea, and partially supported by the Future Semiconductor Device Technology Development Program (10067739) funded by Ministry of Trade, Industry & Energy (MOTIE) and Korea Semiconductor Research Consortium (KSRC), and this study has been conducted with the support of the Korea Institute of Industrial Technology development project (KITECH EO-18-0022). The first two authors (Da-Young Kim and Jaeho Jang) contributed equally to this paper.

Here, we report that Nb doping of two-dimensional (2D) MoSe2 layered nanomaterials is a promising approach to improve their gas sensing performance. In this study, Nb atoms were incorporated into a 2D MoSe2 host matrix, and the Nb doping concentration could be precisely controlled by varying the number of Nb2O5 deposition cycles in the plasma enhanced atomic layer deposition process. At relatively low Nb dopant concentrations, MoSe2 showed enhanced device durability as well as NO2 gas response, attributed to its small grains and stabilized grain boundaries. Meanwhile, an increase in the Nb doping concentration deteriorated the NO2 gas response. This might be attributed to a considerable increase in the number of metallic NbSe2 regions, which do not respond to gas molecules. This novel method of doping 2D transition metal dichalcogenide-based nanomaterials with metal atoms is a promising approach to improve the performance such as stability and gas response of 2D gas sensors.

High-Mn austenitic steels have been recently developed for a storage or transportation application of liquefied natural gas (LNG) in cryogenic fields. Since the structural materials are subjected to extremely low temperature, it requires excellent mechanical properties such as high toughness strength. In case of high-Mn steels, twinning deformation during the cold-working process is known to increase strength yet may cause embrittlement of heavy deformed twin and anisotropic properties. In this study, a recrystallization process through appropriate annealing heat treatments after cold-working was applied to improve the impact toughness for high-Mn austenitic steels. Microstructure and mechanical properties were performed to evaluate the influence of cold-worked and annealed high-Mn austenitic steels. Mechanical properties, such as strength and impact toughness, were investigated by tensile and Charpy impact tests. The relationship between strength and impact toughness was determined by microstructure analysis such as the degree of recrystallization and grain refinement. Consequently, both elongation and toughness were significantly increased after cold-working and subsequent annealing at 1000 &deg, C as compared to the as-received (hot-rolled) specimen. The cold-worked high-Mn steel was completely recrystallized at 1000 &deg, C and showed a homogeneous micro-structure with high-angle grain boundaries.

High-strength steel is widely used in hot forging products for application to the oil and gas industry because it has good mechanical properties under severe environment. In order to apply to the extreme environment industry requiring high temperature and high pressure, heat treatments such as austenitizing, quenching and tempering are required. The microstructure of high-strength steel after heat treatment has various microstructures such as Granular Bainite (GB), Acicular Ferrite (AF), Bainitic Ferrite (BF), and Martensite (M) depending on the heat treatment conditions and cooling rate. Especially in large forged products, the difference in microstructure occurs due to the difference in the forging ratio depending on the location and the temperature gradient according to the thickness during post-heat treatment. Therefore, this study attempted to quantitatively analyze various phases of F70 high-strength steel according to the austenitizing temperature and hot forging ratio using the existing EBSD analysis method. In addition, the correlation between microstructure and mechanical properties was investigated through various phase analysis and fracture behavior of high-strength steel. We found that various microstructures of strength steel depend on the austenitizing temperature and hot forging ratio, and influence the mechanical properties and fracture behavior.

Strontium niobate thin films have potential for next-generation high-k dielectric applications. In this work, we investigated the fabrication of SrxNb1-xOy thin films by atomic layer deposition for the first time and examined their physical and electrical characteristics. The composition of the SrxNb1-xOy thin film could be effectively controlled by introducing a super-cycle, and it was confirmed that the crystallinity after annealing varied depending on the composition. The Sr-rich film was crystalline after annealing and showed a high dielectric constant of approximately 75. In addition, it was observed that the Nb-rich film had a relatively large dielectric constant of approximately 65 even though it was amorphous, confirming that it could be applied as a next-generation high-k material. This research is the first step toward a new high-k dielectric candidate, which we believe can be applied to next-generation semiconductor devices through further research to improve the characteristics.

Plasma-enhanced atomic layer deposition (PEALD) of TiN thin films were investigated as an effective Se diffusion barrier layer for Cu (In, Ga) Se2 (CIGS) solar cells. Before the deposition of TiN thin film on CIGS solar cells, a saturated growth rate of 0.67 Å/cycle was confirmed using tetrakis(dimethylamido)titanium (TDMAT) and N2 plasma at 200 °C. Then, a Mo (≈30 nm)/PEALD-TiN (≈5 nm)/Mo (≈600 nm) back contact stack was fabricated to investigate the effects of PEALD-TiN thin films on the Se diffusion. After the selenization process, it was revealed that ≈5 nm-thick TiN thin films can effectively block Se diffusion and that only the top Mo layer prepared on the TiN thin films reacted with Se to form a MoSe2 layer. Without the TiN diffusion barrier layer, however, Se continuously diffused along the grain boundaries of the entire Mo back contact electrode. Finally, the adoption of a TiN diffusion barrier layer improved the photovoltaic efficiency of the CIGS solar cell by approximately 10%.

Manufacturing high-quality, two-dimensional (2D), layered materials with crystal-growth techniques is an important challenge for the advancement of 2D communication technologies. In this study, a simple method was developed for synthesizing 2D nanocrystals based on the model system of SnS2. The method involves the sulfurization of a metal oxide to a metal chalcogenide, which subsequently acts as a source of vapors for the growth of 2D crystals. The effect of the annealing conditions on the thermal sulfurization of SnO2 powder was investigated. The results showed that pure SnS2 powder could be obtained in a N2 atmosphere at 700 °C. SnS2 nanocrystals were successfully synthesized from the as-prepared SnS2 powder by the vapor transport method. The synthesized SnS2 nanocrystals had a 2D layered structure with hexagonal symmetry and exhibited typical n-type semiconducting characteristics, with an optical band gap of 2.05 eV. This novel method, which uses a preferentially prepared source for vapor transport, co...

SnO 2 thin films were deposited by plasma-enhanced atomic layer deposition (PEALD) using SnCl 4 and O 2 plasma at the temperature between 150 and 350 °C. The self-limiting growth of PEALD-SnO 2 was confirmed by a careful study of the growth kinetics at 350 °C. At optimized growth conditions, PEALD-SnO 2 exhibited a saturated growth per cycle of 0.072 nm/cycle, which is almost two times higher than that deposited by thermal ALD using SnCl 4 reported earlier. Regardless of the growth temperatures, there were no Cl impurities within the films. Furthermore, the film density of rutile SnO 2 was comparable to bulk density. With those favorable properties of PEALD-SnO 2 , the lower electrical resistivity and improved corrosion resistance of the films were obtained at 350 °C.

Vanadium oxide (V 2 O 5-x ) thin films with a thickness of about 4 nm were prepared by atomic layer deposition (ALD) to be used as a hole-transporting layer in an amorphous silicon solar cell. The ALD growth characteristics (growth rate, crystallinity, and surface morphology) of the V 2 O 5-x films were investigated while exposed to different pulse times of ozone (O 3 ), which was used as an oxidant. The effect of the different ozone pulse times, used in the V 2 O 5 layer, on the device performance was also investigated. At the ozone pulse time of 1 s, the maximum value of power conversion efficiency (PCE), i.e., 5.35%, was achieved, whereas at the ozone pulse time of 5 s, the PCE was 4.18%. Ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) analyses confirmed that increasing the proportion of crystalline phase in the V 2 O 4 films with lower work function of V 2 O 5 resulted in decreased open-circuit voltage and conversion efficiency as the ozone pulse time increased.

Owing to the scaling down of dynamic random-access-memory, the development of new high-k dielectrics as well as the reduction in the equivalent-oxide-thickness value using ZrO2 and TiN electrode-based capacitors have become crucial. Because the unwanted interfacial layer between ZrO2 and TiN electrodes can induce the degradation of electrical properties, we propose a new approach for improving capacitor properties by introducing ultrathin metal oxides as the buffers. Each ultrathin TiO2, Ta2O5, and ZnO is inserted between ZrO2 thin films and the top or bottom electrodes, and the variations in their electrical properties are investigated. We discovered that the electrical properties of ZrO2-based capacitors, such as the dielectric constant and leakage current density, can be improved by introducing certain types of buffers without requiring a noble metal electrode and higher-k dielectrics. Furthermore, we discovered that the EOT scaling of approximately 0.15 nm is achievable only through the introduction of the appropriate buffer.

For cryogenic applications, materials must be cautiously selected because of a drastic degradation in the mechanical properties of materials when they are exposed to very low temperatures. We have developed a new technique using a cold-working and surface-cracking process to overcome such degradation of mechanical properties at low temperatures. This technique intentionally induced surface-cracks in cold-worked austenitic stainless steels and resulted in a significant increase in both strength and fracture at low temperatures. According to the microstructure observations, dissipation of the crack propagation energy with surface-cracks enhanced the impact toughness, showing a ductile fracture mode in even the cryogenic temperature region. In particular, we obtained the high strength and toughness materials by a surface-cracking technique at 5% cold-worked specimen with surface-cracks.

A growth technique to directly prepare two-dimensional (2D) materials onto conventional semiconductor substrates, enabling low-temperature, high-throughput, and large-area capability, is needed to realize competitive 2D transition-metal dichalcogenide (TMD)/three-dimensional (3D) semiconductor heterojunction devices. Therefore, we herein successfully developed an atmospheric-pressure plasma-enhanced chemical vapor deposition (AP-PECVD) technique, which could grow MoS2 and WS2 multilayers directly onto PET flexible substrate as well as 4-in. Si substrates at temperatures of

The particle size effect of MgO as a sintering additive on the thermal conductivity of sintered reaction-bonded silicon nitride (SRBSN) was investigated. It was revealed that the size of MgO is critical for thermal conductivity with regard to the microstructural evolution process. That is, the abnormal grain growth promoted by an inhomogeneous liquid-phase distribution led to higher thermal conductivity when coarser MgO was added, whereas a relatively homogeneous liquid-phase distribution induced moderate grain growth and lower thermal conductivity when finer MgO was added.

The dielectric properties of the Si-doped Zr1-xHfxO2 thin films were investigated over a broad compositional range with the goal of improving their properties for use as DRAM capacitor materials. The Si-doped Zr1-xHfxO2 thin films were deposited on TiN bottom electrodes by atomic layer deposition using a TEMA-Zr/TEMA-Hf mixture precursor for deposition of Zr1-xHfxO2 film and Tris-EMASiH as a Si precursor. The Si stabilizer increased the tetragonality and the dielectric constant; however, at high fractions of Si, the crystal structure degraded to amorphous and the dielectric constant decreased. Doping with Si exhibited a larger influence on the dielectric constant at higher Hf content. A Si-doped Hf-rich Zr1-xHfxO2 thin film, with tetragonal structure, exhibited a dielectric constant of about 50. This is the highest value among all reported results for Zr and Hf oxide systems, and equivalent oxide thickness (EOT) value of under 0.5 nm could be obtained with a leakage current of under 10(-7) A·cm(-2), which is the lowest EOT value ever reported for a DRAM storage capacitor system without using a noble-metal-based electrode.

The effect of Al 2 O 3 insertion on the electrical properties of SrTiO 3 films is systemically investigated in metal–insulator–metal (MIM) capacitor because SrTiO 3 films with a high dielectric constant generally suffer from high leakage current problem caused by grain boundaries and a narrow band gap. To find an effective Al 2 O 3 insertion method, Al 2 O 3 is inserted into SrTiO 3 thin films by two different ways. The first method is doping of Al 2 O 3 in SrTiO 3 thin films and the second method is sandwiching a nanometer-thick Al 2 O 3 layer between SrTiO 3 thin films. With respect to leakage blocking properties, the leakage current of Al 2 O 3 -doped SrTiO 3 films is effectively reduced when the SrTiO 3 film becomes amorphous by doping. In case of the SrTiO 3 /Al 2 O 3 /SrTiO 3 structure, an Al 2 O 3 layer with a thickness of more than 1.19 nm effectively acts as a leakage current blocking layer without SrTiO 3 amorphization. Moreover, the degradation of the dielectric properties of Al 2 O 3 -doped SrTiO 3 films is more severe, caused by structural degradation, than of SrTiO 3 /Al 2 O 3 /SrTiO 3 structured films. Therefore, compared with Al 2 O 3 -doped SrTiO 3 , a more than two times higher value (∼45) of the dielectric constant can be obtained in the SrTiO 3 /Al 2 O 3 /SrTiO 3 structured films with a similar leakage current density of 10 −7 A/cm 2 .

Multilayered hard coatings with a CrN matrix and an Al2O3, TiO2, or nanolaminate-Al2O3/TiO2 sealing layer were designed by a hybrid deposition process combined with physical vapor deposition (PVD) and atomic layer deposition (ALD). The strategy was to utilize ALD thin films as pinhole-free barriers to seal the intrinsic defects to protect the CrN matrix. The influences of the different sealing layers added in the coatings on the microstructure, surface roughness, and corrosion behaviors were investigated. The results indicated that the sealing layer added by ALD significantly decreased the average grain size and improved the corrosion resistance of the CrN coatings. The insertion of the nanolaminate-Al2O3/TiO2 sealing layers resulted in a further increase in corrosion resistance, which was attributed to the synergistic effect of Al2O3 and TiO2, both acting as excellent passivation barriers to the diffusion of corrosive substances.

2D layered materials with sensitive surfaces are promising materials for use in chemical sensing devices, owing to their extremely large surface-to-volume ratios. However, most chemical sensors based on 2D materials are used in the form of laterally defined active channels, in which the active area is limited to the actual device dimensions. Therefore, a novel approach for fabricating self-formed active-channel devices is proposed based on 2D semiconductor materials with very large surface areas, and their potential gas sensing ability is examined. First, the vertical growth phenomenon of SnS2 nanocrystals is investigated with large surface area via metal-assisted growth using prepatterned metal electrodes, and then self-formed active-channel devices are suggested without additional pattering through the selective synthesis of SnS2 nanosheets on prepatterned metal electrodes. The self-formed active-channel device exhibits extremely high response values (>2000% at 10 ppm) for NO2 along with excellent NO2 selectivity. Moreover, the NO2 gas response of the gas sensing device with vertically self-formed SnS2 nanosheets is more than two orders of magnitude higher than that of a similar exfoliated SnS2 -based device. These results indicate that the facile device fabrication method would be applicable to various systems in which surface area plays an important role.

Multilayered hard coatings with a CrN matrix and an Al2O3, TiO2, or nanolaminate-Al2O3/TiO2 sealing layer were designed by a hybrid deposition process combined with physical vapor deposition (PVD) and atomic layer deposition (ALD). The strategy was to utilize ALD thin films as pinhole-free barriers to seal the intrinsic defects to protect the CrN matrix. The influences of the different sealing layers added in the coatings on the microstructure, surface roughness, and corrosion behaviors were investigated. The results indicated that the sealing layer added by ALD significantly decreased the average grain size and improved the corrosion resistance of the CrN coatings. The insertion of the nanolaminate-Al2O3/TiO2 sealing layers resulted in a further increase in corrosion resistance, which was attributed to the synergistic effect of Al2O3 and TiO2, both acting as excellent passivation barriers to the diffusion of corrosive substances.

Highlights: • Ti doped ZnO films were prepared on Corning XG glass substrate by ALD. • The electrical properties and optical properties were systematically investigated. • An optimized Ti doped ZnO films had low resistivity and excellent optical transmittance. - Abstract: Titanium doped zinc oxide (Ti doped ZnO) films were prepared by atomic layer deposition methods at a deposition temperature of 200 °C. The Ti content in Ti doped ZnO films was varied from 5.08 at.% to 15.02 at.%. X-ray diffraction results indicated that the crystallinity of the Ti doped ZnO films had degraded with increasing Ti content. Transmission electron microscopy was used to investigate the microstructural evolution of the Ti doped ZnO films, showing that both the grain size and crystallinity reduced with increasing Ti content. The electrical resistivity of the Ti doped ZnO films showed a minimum value of 1.6 × 10{sup −3} Ω cm with the Ti content of 6.20 at.%. Furthermore, the Ti doped ZnO films exhibited excellent transmittance.

We demonstrated a novel porous Ni foam (PNF) with small voids/pores penetrating the skeleton wall by a simple etching process using commercial Ni foam, aiming to achieve the maximum use of its hollow structure for various nanostructured materials growing as the electrode for supercapacitor application. The hydrothermal Ni(OH)2 nanosheets, functioning as the battery-type active material, were successfully grown vertically on both inner and outer surface of the PNF skeleton. The Ni(OH)2/PNF electrodes exhibited high capacity of ∼578 C/g at 1 A/g current density with capacitance retention of ∼90% after 3000 cycles, which was much higher than those of the Ni(OH)2/NF electrodes. The strategy suggests that 3D PNF not only provides a universal route for the rational design of biface (inner and outer) growth of various nanostructured electrode materials, but also reducing the total mass of the electrode supporter by take full advantage of the hollow structure of Ni foam for the industrial applications.

ZnO films were deposited by the PEALD using oxygen and hydrogen plasmas at 100 °C. As the oxygen plasma increased by 200 W, the growth rate saturated to 1.78 A/cycle over 150 W. The film resistivity increased to 4.95 × 10 3 Ω cm without a significant change of film crystallinity but the carrier concentration drastically decreased to 4.87 × 10 13 cm −3 as the oxygen plasma power increased to 200 W. Interestingly, as the hydrogen plasma power increased during ZnO PEALD (DEZ + O 2 plasma + H 2 plasma), the growth rate, film crystallinity and resistivity drastically decreased. Although the crystallinity of z -axis ZnO film decreased, the ZnO film exhibited the conducting property. Based on x-ray photoelectron spectroscopy and auger electron spectroscopy analysis, the higher oxygen plasma power may help to decrease oxygen vacancies but the higher hydrogen plasma power can induce in generation oxygen vacancies and hydroxyl groups in ZnO films, strongly relating with the changes of carrier concentrations. The hydrogen and oxygen plasma exhibited conflicting behaviors in terms of ZnO electrical property. Thus, the electrical properties on ZnO film PEALD are easily manipulated even on very low deposition temperature, with only selecting oxygen and hydrogen plasma conditions.

Thermal stability of RuO2 thin films formed by modified atomic layer deposition on SiO2 substrate was investigated. Rapid thermal annealing was conducted for 2 min under NH3 and N2 ambient. It was demonstrated that NH3 gas can completely reduce RuO2 to pure Ru at a relatively low annealing temperature of 500 °C, while partial reduction of RuO2 into Ru at the outmost surface was observed after N2 annealing. Agglomeration of the NH3 annealed film was not observed due to high quality of the as-deposited film that was dense and had low level of impurities such as hydrogen and carbon.

Ruthenium–aluminum-nitride (Ru–AlN) thin films were grown by plasma-enhanced atomic layer deposition (PEALD) at 300 °C. The Ru intermixing ratio of Ru–AlN thin films was controlled by the number of Ru unit cycles, while the number of AlN unit cycles was fixed to one cycle. The electrical resistivity of Ru–AlN thin film decreased with increasing the Ru intermixing ratio, but a drastic decrease in electrical resistivity was observed when the Ru intermixing ratio was around 0.58–0.78. Bright-field scanning transmission electron microscope (BF-STEM) and energy-dispersive X-ray spectroscopy (EDX) element mapping analysis revealed that the electrical resistivity of Ru–AlN thin film was strongly dependent on the microstructures as well as on the Ru intermixing ratio. Although the electrical resistivity of Ru–AlN thin films decreased with increasing the Ru intermixing ratio, a drastic decrease in electrical resistivity occurred where the electrical paths formed as a result of the coalescence of Ru nanocrystals.

We report the successful synthesis of surface defective small size (SS) SnO2 nanoparticles (NPs) by adopting a low temperature surfactant free solution method. The structural properties of the NPs were analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The presence of surface defects, especially oxygen vacancies, in the sample were characterized using micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence emission. The Brunauer–Emmet–Teller (BET) nitrogen adsorption–desorption isotherms demonstrated the superior textural properties (high surface area and uniform pore size) of SS SnO2 compared to large size (LS) SnO2. A comparable study was drawn between SS SnO2 and LS SnO2 NPs and a significant decrease in the concentration of surface defects was observed for the LS sample. The results showed that surface defects significantly depend upon the size of the NPs. The surface defects formed within the band gap energy level of SnO2 significantly participated in the recombination process of photogenerated charge carriers, improving photochemical properties. Moreover, the SS SnO2 showed superior photoelectrochemical (PEC) and photocatalytic activities compared to the LS SnO2. The presence of a comparatively large number of surface defects due to its high surface area may enhance the photochemical activity by reducing the recombination rate of the photogenerated charges.

Hybrid functional RuO2–Al2O3 thin films were prepared by atomic layer deposition using bis(ethylcyclopentadienyl)ruthenium (Ru(EtCp)2) and trimethyl aluminum (TMA). The intermixing ratios between RuO2 and Al2O3 in the RuO2–Al2O3 thin films were controlled from (RuO2)0.16–(Al2O3)0.84 to (RuO2)0.72–(Al2O3)0.28. With the RuO2 intermixing ratio less than 0.43, both temperature coefficient of resistance (TCR) values and resistivities were abruptly changed. The TCR values for RuO2–Al2O3 thin films were changed from −381 to −62.3 ppm/K by changing the RuO2 intermixing ratios from 0.43 to 0.83, while the resistivities were also changed from 1,200 to 243 μΩ·cm. Moreover, the change in the TCR of RuO2–Al2O3 thin films was below 127 ppm/K even after O2 annealing process at 700 °C. Moreover, it showed that RuO2–Al2O3 thin films had a high corrosion resistance due to the highly corrosion-resistive RuO2 and Al2O3.

Ti–Al–Si–N films were deposited on WC–Co substrates by a hybrid coating system. The synthesized Ti–Al–Si–N films were revealed to be composites of solid-solution (Ti,Al,Si)N crystallites and amorphous Si 3 N 4 by instrumental analyses such as XRD and HRTEM. The highest micro-hardness value (50 GPa) was obtained from the Ti–Al–Si–N film having the Si content of 9 at.%, the microstructure of which was characterized by a nanocomposite of nc-(Ti,Al,Si)N/a-Si 3 N 4 . The tool lives of Ti–Al–Si–N coated tool for AISI D2 steel of hardness 62 HRC were studied under various cutting speeds in high speed machining center. Tool wear curves with cutting length were presented.

We thank G. S. Kim and J.-H. Ahn for assistance with thin film depositions, and S. S. Bae for assistance with SEM analysis. This work was supported by the second stage of the Brain Korea 21 Project, the Korea Research Foundation (KRF-2005-003-D00085), the Basic Research Program of the Korea Science & Engineering Foundation (R01-2005- 000-10456-0), the Korean Ministry of Science and Technology, and the Korean Ministry of Science and Technology and Fundamental R&D Program for Core Technology of Materials funded by the Korean Ministry of Commerce, Industry and Energy. Also, this work was partially supported by grants-in-aid for the National Core Research Center Program from MOST/KOSEF (No. R15-2006-022-01001-0).

Because of its excellent charge carrier mobility at the Dirac point, graphene possesses exceptional properties for high-performance devices. Of particular interest is the potential use of graphene nanoribbons or graphene nanomesh for field-effect transistors. Herein, highly aligned DNA nanowire arrays were crafted by flow-assisted self-assembly of a drop of DNA aqueous solution on a flat polymer substrate. Subsequently, they were exploited as "ink" and transfer-printed on chemical vapor deposited (CVD)-grown graphene substrate. The oriented DNA nanowires served as the lithographic resist for selective removal of graphene, forming highly aligned graphene nanoribbons. Intriguingly, these graphene nanoribbons can be readily produced over a large area (i.e., millimeter scale) with a high degree of feature-size controllability and a low level of defects, rendering the fabrication of flexible two terminal devices and field-effect transistors.