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High-Mn (over 24 wt%) austenitic steels recently have been developed with excellent mechanical properties such as high strength and ductility at very low temperatures for cryogenic application. Especially, cold-rolling process is and effective method to increased yield and tensile strength of high-Mn steel when making products. In our previous work, we have investigated the correlation between microstructure and mechanical properties due to recrystallization without considering the characteristics of the cold-rolling direction of high-Mn steels. In this study, we evaluated the effects of anisotropic behaviors on the heat treatment of cold-rolling high-Mn steels. Despite the heat treatment, differences between transverse and longitudinal direction in the cold-rolled conditions generally affected the recrystallized microstructure. Such anisotropic behaviors caused changes in mechanical properties such as tensile and Charpy impact test, as microstructure along cold-rolling direction.

Zero-dimensional/two-dimensional (0D/2D) TiO2/g-C3N4 heterostructural photocatalysts were fabricated via ALD technique. TiO2 nanoparticles were “site-selectively grown” on g-C3N4 nanosheets and the surface modification induced band engineering of the composite photocatalysts. Thus, the redox properties of the photocatalysts were fine tuned. Under visible light, since only g-C3N4 was excited, TiO2 was acting as the electron transport channel in the optimized interfacial structures. They effectively suppressed the recombination and facilitated the transfer of photogenerated charges, improving the photocatalytic activity. When both the components were excited under UV–vis light, the dynamic equilibrium of the conduction band positions on these n–n type semiconductor heterojunctions led to the increased recombination rate of charges, decreasing the reactivity for H2 evolution. However, the photocatalytic degradation of organic pollutants by these composite photocatalysts exhibited enhanced activities, resulting from the photogenerated holes on VB of TiO2 which could promote oxidation of organic pollutants with strong oxidation potentials. Furthermore, TiO2/g-C3N4 photocatalysts with limited numbers of deposition cycles exhibited optimal photocatalytic activity under visible light. In contrast, excessive deposition cycles on g-C3N4 for TiO2/g-C3N4 led to continuous film and increased thickness of TiO2, resulting in the attenuation of the reactivity. We verified this TiO2/g-C3N4 photocatalysts with less mass-loading, but more enhanced photocatalytic activity.

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 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.

The wear resistance of Ti1−xMexN (Me = Zr, Al, Cr) coatings by the laser carburization process was investigated in terms of local atomic structural changes. The repeated pulsed laser ablation was performed to the Ti1−xMexN coating surfaces after Graphite paste was covered. The friction coefficients of the coating specimens were decreased from ∼0.7 to 0.2, and the formation of cracks and debris was suppressed by implementing the laser ablation process. ToF-SIMS depth profiles showed that the laser carburization helps Carbon penetrate into the coating layer as deep as ∼20 nm below its surface. XPS and XAFS analyses revealed that the improvement of the wear resistance of the coatings was achieved not by formation of TiC or ZrC lattices on the coatings surfaces but by Carbon interstitials to the Ti1−xMexN lattices.

The mechanism of hardness improvement of a TiZrN coating by carbon doping was investigated in terms of the residual stress and the lattice deformation. Carbon was doped using laser carburization to improve the hardness of TiZrN, which was increased from 3025 HV to 3388 HV. The lattice parameter was calculated through Rietveld refinement in order to analyze the behavior inside the lattice due to carbon doping, which showed that the parameter increased from 4.21 A to 4.44 A after the carbon doping process. The diffraction pattern was analyzed using an electron beam to identify the lattice state of the coating layer, and lattice distortion was revealed through a diffused ring pattern. The compressive residual stress was increased by 48%, which was identified through the sin2Ψ method using the lattice constant change due to carburization. After the carbon doping, the hardness of the TiZrN was increased by 10%, which was attributed to the expansion distortion generated in the TiZrN lattice and the increase of the compressive residual stress.

Diamond-like carbon (DLC) coatings with AlTiSi multi-doping were prepared by a reactive high power impulse magnetron sputtering with using a gas mixture of Ar and C2H2 as precursor. The composition, microstructure, compressive stress, and mechanical property of the as-deposited DLC coatings were studied systemically by using SEM, XPS, TEM, Raman spectrum, stress-tester, and nanoindentation as a function of the Ar fraction. The results show that the doping concentrations of the Al, Ti and Si atoms increased as the Ar fraction increased. The doped Ti and Si preferred to bond with C while the doped Al mainly existed in oxidation state without bonding with C. As the doping concentrations increased, TiC carbide nanocrystals were formed in the DLC matrix. The microstructure of coatings changed from an amorphous feature dominant AlTiSi-DLC to a carbide nanocomposite AlTiSi-DLC with TiC nanoparticles embedding. In addition, the coatings exhibited the compositionally modulated multilayer consisting of alternate Al-rich layer and Al-poor layer due to the rotation of the substrate holder and the diffusion behavior of the doped Al which tended to separate from C and diffuse towards the DLC matrix surface owing to its weak interactions with C. The periodic Al-rich layer can effectively release the compressive stress of the coatings. On the other hand, the hard TiC nanoparticles were conducive to the hardness of the coatings. Consequently, the DLC coatings with relatively low residual stress and high hardness could be acquired successfully through AlTiSi multi-doping. It is believed that the AlCrSi multi-doping may be a good way for improving the comprehensive properties of the DLC coatings. In addition, we believe that the DLC coatings with Al-rich multilayered structure have a high oxidation resistance, which allows the DLC coatings application in high temperature environment.

Although MXenes with outstanding electrical conductivity possess great potential as energy-storage materials for flexible supercapacitors (SCs), the electrochemical performance of the pure MXene-based SCs are often restricted by inherent limitations such as inferior energy densities and serious aggregation. Alternatively, it will be an effective strategy to develop rationally designed composite electrodes that can simultaneously provide both high electrical conductivity and large surface area via complementary functions of each constituent. Here, hierarchically layered MXene nanosheets on nickel cobalt sulfide/carbon cloth (Ti3C2Tx/NiCo2S4@CC, herein TNSC) was prepared through spray injection of MXene on nickel cobalt sulfide, which not only achieved an excellent specific capacitance at high current densities but also possess improved cycling stability. The optimized TNSC electrode shows maximum specific capacities of 2326F g−1 at a current density of 1 A g−1, and excellent cycling stability of 93.8% at 10 A g−1. We show that these outstanding electrochemical performances can be achieved by a proper loading amount of surface-coated Ti3C2Tx, which can simultaneously enhance electrical conductivity and permeate ions to nickel cobalt sulfide. Furthermore, a quasi-solid‐state flexible SC (QFSC) based on TNSC presents a high energy density of 57.5 W h kg−1 at a power density of 800 W kg−1 in a wide potential window of 1.6 V. Therefore, the excellent electrochemical performances of the TNSC electrode makes it as a prominent candidate for high-performance and flexible energy storage devices.

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...

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.

A high dielectric constant (k = 22.5) Al-doped HfO2 film was prepared on Si substrate by plasma-enhanced atomic layer deposition (PEALD) at a reduced thickness of ~ 30 nm by realizing a (200) preferentially oriented tetragonal structure. The realization of a (200) preferred orientation was able to be obtained by the interface control in PEALD. When using a conventional supercycle that consisted of the Al2O3 and HfO2 subcycles, the dielectric constants of tetragonal Al-doped HfO2 films rapidly decreased from 37 to 8.5 as the film thickness decreased from ~ 92 to ~ 9 nm due to the change of the preferred orientation from (200) to (111). To obtain (200) preferentially oriented tetragonal Al-doped HfO2 thin films at highly thin thickness, a modified supercycle that consisted of the Hf-Al-O subcycle and the HfO2 subcycle was designed to increase Al dopant distribution in HfO2 films. As a result, a (200) preferentially oriented tetragonal Al-doped HfO2 films with a high dielectric constant of 22.5 was obtained at a reduced thickness of ~ 30 nm. Also, the leakage current densities of the Pt/~ 30 nm-thick-tetragonal Al-doped HfO2 films/Si capacitor were about 10-5 A/cm2 for a field strength of -1 MV/cm due to the crystallization after N2 annealing process.

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.

The stainless steel (SS)-based bipolar plate with high conductivity and corrosion resistance is one of the key components in recent polymer electrolyte membrane fuel cells. Therefore, an excellent corrosion protection and good electrical conductivity in SS316L-based bipolar plates can be achieved through plasma-enhanced atomic layer deposition (PEALD) of ultrathin (25–67 nm) TiN thin films. To this end, two types of TiN protective coatings deposited by PEALD using tetrakis(dimethylamino)titanium (TDMAT) and titanium tetrachloride (TiCl4) precursors were evaluated; the evaluations were conducted under conditions simulating the operating conditions of PEMFCs. Regardless of the precursor type, PEALD-TiN onto SS316L resulted in great improvements in electrical conductivity and corrosion resistance. Notably, the TiN thin films prepared using TDMAT exhibited excellent corrosion resistance (

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.

Plasma-enhanced atomic layer deposition (PEALD) of tantalum nitride (TaN) thin films was investigated at a growth temperature of 230 °C using an alternating supply of tertiary-amylimido-tris(dimethylamido)tantalum (TAIMATA, Ta[NC(CH3)2C2H5][N(CH3)2]3) and hydrogen (H2) plasma. As the H2 plasma power increased from 75 to 175 W, the electrical resistivity of the films was improved from 1900 to 680 μΩ·cm, mainly due to the improved crystallinity. Moreover, the preferred orientation ratio between TaN (200) and TaN (111) planes also abruptly increased from 0.8 to 2.8 with increasing the H2 plasma power. This preferred orientation change of the films from (111) to (200) improves the adhesion properties between Cu and TaN, while the Cu diffusion barrier performance was not significantly affected.

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.

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.

Using the high working pressure plasma-enhanced chemical vapor deposition (HWP-PECVD) technique, the hydrogenated microcrystalline silicon (μc-Si:H) films for photovoltaic layers of thin film solar cells was investigated. The $\pmb{\mu \mathrm{c}-\mathrm{Si}:\mathrm{H}}$ films were deposited on surface textured fluorine-doped tin oxide (FTO) glass substrates at 100 Torr in a 100 MHz very high frequency (VHF) plasma of gas mixtures containing He, H2, and SiH4. It was found that an optimum ratio of the H2/SiH4 flowrate existed for growing a homogenous microcrystalline through the whole film without amorphous incubation layer. When an intrinsic $\pmb{\mu \mathrm{c}-\mathrm{Si}:\mathrm{H}}$ thin film was deposited at n-i-p single junction solar cell, the cell performances were dependent on with or without an amorphous incubation layer. With an amorphous incubation layer, the open circuit voltage $(\mathrm{V}_{\mathrm{oc}})$ of cell was 0.8V, which was typical cell property of hydrogenated amorphous silicon (a-Si:H). On the other hand, at the optimum ratio of the H2/SiH4 flow-rate, μc-Si:H single cell responding an infrared light showed the Voc of 0.49 V. Intrinsic hydrogenated microcrystalline silicon (μc-Si:H) thin film, exhibiting the photovoltaic performance (Eff: 7.2%, $\pmb{\mathrm{V}_{\mathrm{oc}}:0.49\mathrm{V}, \mathrm{J}_{\mathrm{sc}}:23\mathrm{mA}/\mathrm{cm}^{2}}$ , FF:64%) was able to be successfully fabricated.

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.

5-nm-scale line and hole patterning is demonstrated by synergistic integration of block copolymer (BCP) lithography with atomic layer deposition (ALD). While directed self-assembly of BCPs generates highly ordered line array or hexagonal dot array with the pattern periodicity of 28 nm and the minimum feature size of 14 nm, pattern density multiplication employing ALD successfully reduces the pattern periodicity down to 14 nm and minimum feature size down to 5 nm. Self-limiting ALD process enable the low temperature, conformal deposition of 5 nm thick spacer layer directly at the surface of organic BCP patterns. This ALD assisted pattern multiplication addresses the intrinsic thermodynamic limitations of low χ BCPs for sub-10-nm scale downscaling. Moreover, this approach offers a general strategy for scalable ultrafi ne nanopatterning without burden for multiple overlay control and high cost lithographic tools.

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.

Ru-AlN thin films were suggested as a novel multifunctional heating resistor film for non-passivated type thermal inkjet printer devices. Ru-AlN thin films were prepared by plasma-enhanced atomic layer deposition in order to intermix Ru and AlN precisely. When the Ru intermixing ratios were optimized, Ru-AlN films showed a favorable electrical resistivity (from 490.9 to 75.3 μΩcm) and minimized temperature coefficient of resistance (TCR) values (from 335 to 360 ppm/K). Moreover, the Ru-AlN films showed a strong oxidation resistant as compared with commercially used TaN0.8 films because the prepared Ru-AlN thin films had a typical nanocomposite structure. By applying electrical pulses to the heater device using Ru-AlN thin films for a Joule heating, a reliable operation was also proven.

Various copper oxide films were successfully grown by plasma-enhanced atomic layer deposition (PEALD) at a low temperature of 100 °C. X-ray diffraction analysis of the films indicated that phase-controlled deposition of CuOx phases (0 ≤ x < 1) was possible by controlling the number of Cu deposition steps during one PEALD cycle with a fixed oxidation step. When Cu deposition was executed in one step, an amorphous CuOx (x = 0.9) film with a smooth surface (RMS roughness of 0.97 nm) was obtained. On the other hand, when the number of Cu deposition steps was increased to three, a CuOx (x = 0.6) thin film with a polycrystalline phase (grain size: 25 nm) was obtained. The as-deposited CuO0.6 film showed p-type conductivity (Hall mobility ∼37 cm2/V·s and hole concentration ∼5.4 × 1014 cm−3). Moreover, p-type CuO0.6/n-type ZnO heterojunction diodes fabricated on a flexible polyethylene terephthalate substrate exhibited electrical rectification with a threshold voltage of 1.2 V.

Si3N4/SiC nanocomposites are well known and attractive for advanced ceramic applications due to excellent mechanical and thermal properties, which make them suitable for use in turbine engines, heat exchangers, and other sophisticated applications. However, without the presence of additives, the fabrication of Si3N4/SiC composites is difficult. The additives form a liquid phase during sintering and facilitate the densification of the composite. However, the additives present a drawback at high temperatures since they decrease the mechanical properties of the composites. Recently, Si3N4/SiC composites were fabricated via the polymer precursor route without any additives, using electric field assisted sintering (EFAS). In this study, fully densified Si3N4/SiC nanocomposites incorporating hexagonal-BN were successfully fabricated by hot pressing without any additives at 1700 °C for 2 h under vacuum at a pressure of 50 MPa (via the amorphous precursor route). Moreover, the incorporation of additives and h-BN is found to decrease the content of SiC. The phase transformation, densification, microstructure, and mechanical properties were discussed and presented.

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.

Ru films were produced by atomic layer deposition (ALD) with an alternating supply of bis(ethylcyclopentadienyl)ruthenium (Ru(EtCp)2) and ozone at deposition temperatures of 225‐275 ◦ C. Ozone acted as an effective reactant for Ru(EtCp)2 .T he Ru fi lm thicknesses formed during one cycle were saturated at relatively high values of 0.09‐0.12 nm/cycle depending on the deposition temperatures, and their resistivities were about 16 μ cm. Moreover, a reduced nucleation delay was found for Ru ALD using ozone when compared to Ru ALD using oxygen gas. The amount of oxygen impurity incorporated into the Ru films was less than 1 at%, as determined by Auger electron spectroscopy. The interfacial adhesion property between Ru films prepared via ALD using ozone (ozone-Ru) and ZrO2 was good and 80% step coverage was achieved on a 3-D structure with a very high aspect ratio of 16:1, making them suitable for use as a top electrode material.

A novel burning technique for making a semiconducting single-walled carbon nanotubes (SWNTs) transistor assembled by the dielectrophoretic force was suggested. The fabrication process consisted of two steps. First, to align and attach a bundle of SWNTs between the source and drain, the alternating (AC) voltage was applied to the electrodes. When a bundle of SWNTs was connected between two electrodes, some of metallic nanotubes and semi-conducing nanotubes existed together. The second step is to burn the metallic SWNTS by applying the voltage between two electrodes. With increasing the voltage, more current flowed through the metallic SWNTs, thus, the metallic SWNTs burnt earlier than the semiconducting one. This technique enables to obtain only semi-conducting SWNTs connection in the transistor. Through the I-V characteristic graph, the moment of metallic SWNTs burning and the characteristic of semi-conducing nanotubes were verified.

A systematic investigation of the microstructure of CrAlCxN1-x coatings as a function of carbon contents was conducted. Quaternary CrAlCxN1-x coatings were deposited on Si wafers by a hybrid coating system combining an arc-ion plating technique and a DC reactive magnetron sputtering technique using Cr and Al targets in the Ar/N2/CH4 gaseous mixture. The effect of carbon content on microstructure of CrAlCxN1-x coatings was investigated with instrumental analyses of X-ray diffraction, X-ray photoelectron, and high-resolution transmission electron microscopy. The results show that the carbon content of CrAlCxN1-x coatings linearly increases with increasing CH4/(CH4/N2) gas flow rate ratio. The surface roughness of the CrAlCxN1-x coating layer decreases with the increase of carbon content.

Cr-Al-Si-N coatings were deposited on SUS 304 substrate by a hybrid coating system. A Cr interlayer was introduced between Cr-Al-Si-N coating and SUS 304 substrate to improve the coating adherence. The effects of Cr interlayer on the microhardness, adhesion, and tribological behavior of Cr-Al-Si-N coatings were systematically investigated. The results indicate that the microhardness of the Cr-Al-Si-N coatings gradually deceases with increasing thickness of Cr interlayers. The adhesion between Cr-Al-Si-N and SUS 304 substrate is improved by addition of the Cr interlayers. A peak critical load of ∼50 N is observed for the coating containing Cr interlayer of 60 nm as compared ∼ 20 N for the coating without Cr interlayer. The thicker Cr interlayers result in reduced critical load values. Moreover, the wear resistance of the Cr-Al-Si-N coatings is greatly enhanced by introducing the Cr interlayer with thickness of 60 nm in spite of the decreased microhardness. The friction coefficient of the coating system is also moderately reduced.

As a solid lubricant, silver-palladium (Ag-Pd) alloy coating was investigated for the application to high temperature stud bolt. A glue layer nickel (Ni) film was deposited on the surface of the hex bolt sample and then Ag-Pd alloy coating was performed on it using ion plating method. The friction coefficient of Ag-Pd alloy film coated bolt was lower than that of N-5000 oil coated bolt by the result of axial force measurement. The cyclic test of heat treatment was conducted to evaluate the durability of Ag-Pd alloy film coated bolt. In a cycle, sample was assembled into the block using torque wrench, followed by heating and disassembling. It was not successful to disassemble the N-5000 oil coated bolt from the block after only one cycle. However, the Ag-Pd alloy film coated bolt was able to be disassembled softly till 12 cycles.

Applying negative bias voltages caused significant microstructure changes in arc ion plated CrN films. Nanocrystalline microstructures were obtained by adjusting the negative bias voltage. Structural characterizations of the films were carried out using X-ray diffractometry (XRD) and high-resolution transmission electron microscopy (HR-TEM). The results indicated that increasing ion bombardment by applying negative bias voltages resulted in the formation of defects in the CrN films, inducing microstructure evolution from micro-columnar to nanocrystalline. The microhardness and residual stresses of the films were also affected. Based on the experimental results, the evolution mechanisms of the film microstructure and properties were discussed by considering ion bombardment effects.

IrO2-TiO2 thin films were prepared by atomic layer deposition using Ir(EtCp)(COD) and titanium isopropoxide (TTIP). The resistivity of IrO2-TiO2 thin films can be easily controlled from 1 500 to 356.7 μωcm by the IrO2 intermixing ratio from 0.55 to 0.78 in the IrO2-TiO2 thin films. The low temperature coefficient of resistance(TCR) values can be obtained by adopting IrO2-TiO2 composite thin films. Moreover, the change in the resistivity of IrO2-TiO2 thin films was below 10% even after O2 annealing process at 600 °C. The step stress test results show that IrO2-TiO2 films have better characteristics than conventional TaN0.8 heater resistor. Therefore, IrO2-TiO2 composite thin films can be used as a heater resistor material in thermal inkjet printhead.

The study on damaged layer is necessary for improving the machinability in micro-machining because the damaged layer affects the micro mold life and micro machine parts. This study examined the ultra-precision micro-machining characteristics, such as cutting speed, feed rate and cutting depth, of a micro-damaged layer produced by an ultra-high speed air turbine spindle. The micro cutting force, surface roughness and plastic deformation layer were investigated according to the machining conditions. The damaged layer was measured using optical microscope on samples prepared through metallographic techniques. The scale of the damaged layer depends on the cutting process parameters, particularly, the feed per tooth and axial depth of the cut. According to the experimental results, the depth of the damaged layer is increased by increasing the feed per tooth and cutting depth, also the damaged layer occurs less in down-milling compared with up-milling during the micro-machining operation.

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.

Cr–Mo–Si–N coatings were prepared on Si wafer by a hybrid coating system combining arc ion plating and magnetron sputtering at the substrate bias voltage ranging from 0 to − 400 V. The results showed that the deposition rate, film microstructure, and properties of the coatings was significantly altered with increase of bias voltage. The deposition rate changing from 2.2 to 1.6 μm/h was observed due to the resputtering effect. Only CrN phase can be detected in the XRD spectra of all the Cr–Mo–Si–N coatings. Grain size diminishment and orientation transformation from (200) preferred to random was observed with increase of bias voltage. The maximum microhardness of about 49 GPa was obtained at the bias voltage of − 50 V. The internal stress in Cr–Mo–Si–N coatings was compressive and ranging from − 1.2 to − 2.7 GPa. The microhardness enhancement was discussed considering grain size diminishment and residual stress in the coatings. The surface topography of the Cr–Mo–Si–N coatings was also investigated in this study.

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.

Sn thin films were grown by DC magnetron sputtering on a soda-lime glass and Si substrate. The in-situ electrical resistance of the films was measured during the film growth. The minimum continuous thickness of the films was difficult to determine by using the conventional plot of R × d 2 versus d and could only be approximately calculated to be near 20 to 25 nm. On the other hand, a new empirical method using the plot of R × d 3 versus d gave a value of 16 nm for the minimum continuous Sn film thickness. The minimum continuous thickness of Sn films obtained from field-emission scanning electron microscopy and X-ray photoemission spectroscopy analyses was 16 nm. The new empirical method proposed here has the potential to determine the exact minimum continuous thickness of the films.

In this study, highly hierarchically porous NiO nanosheet arrays were synthesized on glass by a hydrothermal growth method. The effects of temperature and the reactant concentrations on the morphology of the nanosheets were examined. SEM revealed uniform and hierarchical porous NiO nanosheets at 50 mM of a nickel nitrate hexahydrate solution at 90 °C in 2 h. After heat treatment in oxygen at 450 °C for 1 h, the resistivity of the annealed NiO nanosheet samples was five orders of magnitude lower than the as-prepared samples. In addition, the resistivity of the nanosheet arrays decreased significantly with increasing reactant concentration. The hierarchically porous nanosheets synthesized under optimal conditions were 200–400 nm in thickness and 6–8 μm in height. These nanosheets might have potential electrochromic applications.

Small machines are highly promising for future medicine and new materials. Recent advances in functional nanomaterials have driven the development of synthetic inorganic micromachines that are capable of efficient propulsion and complex operation. Miniaturization and large-scale manufacturing of these tiny machines with true nanometer dimension are crucial for compatibility with subcellular components and molecular machines in operation. Here, block copolymer lithography is combined with atomic layer deposition for wafer-scale fabrication of ultrasmall coaxial TiO2/Pt nanotubes as catalytic rocket engines with length below 150 nm and a tubular reactor size of only 20 nm, leading to the smallest man-made rocket engine reported to date. The movement of the nanorockets is examined using dark-field microscopy particle tracking and dynamic light scattering. The high catalytic activity of the Pt inner layer and the reaction confined within the extremely small nanoreactor enable highly efficient propulsion, achieving speeds over 35 µm s−1 at a low Reynolds number of

Ru-TiN thin films were prepared from bis(ethylcyclopentadienyl)ruthenium and tetrakis(dimethylamino)titanium using plasma-enhanced atomic layer deposition (PEALD). The Ru and TiN were deposited sequentially to intermix TiN with Ru. The composition of Ru-TiN films was controlled precisely by changing the number of deposition cycles allocated to Ru, while fixing the number of deposition cycles allocated to TiN. Although both Ru and TiN thin films have a polycrystalline structure, the microstructure of the Ru-TiN films changed from a TiN-like polycrystalline structure to a nanocrystalline on increasing the Ru intermixing ratio. Moreover, the electrical resistivity of the Ru0.67-TiN0.33 thin films is sufficiently low at 190 microomega x cm and was maintained even after O2 annealing at 750 degrees C. Therefore, Ru-TiN thin films can be utilized as a oxygen diffusion barrier material for future dynamic (DRAM) and ferroelectric (FeRAM) random access memory capacitors.