Effect of GNWs/NiO-WO3/GNWs Heterostructure for NO2 Gas Sensing at Room Temperature.

Recently, as air pollution and particulate matter worsen, the importance of a platform that can monitor the air environment is emerging. Especially, among air pollutants, nitrogen dioxide (NO2) is a toxic gas that can not only generate secondary particulate matter, but can also derive numerous toxic gases. To detect such NO2 gas at low concentration, we fabricated a GNWs/NiO-WO3/GNWs heterostructure-based gas sensor using microwave plasma-enhanced chemical vapor deposition (MPECVD) and sputter, and we confirmed the NO2 detection characteristics between 10 and 50 ppm at room temperature. The morphology and carbon lattice characteristics of the sensing layer were investigated using field emission scanning electron microscopy (FESEM) and Raman spectroscopy. In the gas detection measurement, the resistance negative change according to the NO2 gas concentration was recorded. Moreover, it reacted even at low concentrations such as 5-7 ppm, and showed excellent recovery characteristics of more than 98%. Furthermore, it also showed a change in which the reactivity decreased with respect to humidity of 33% and 66%.

Growth Properties of Carbon Nanowalls on Nickel and Titanium Interlayers.

This research is conducted in order to investigate the structural and electrical characteristics of carbon nanowalls (CNWs) according to the sputtering time of interlayers. The thin films were deposited through RF magnetron sputtering with a 4-inch target (Ni and Ti) on the glass substrates, and the growth times of the deposition were 5, 10, and 30 min. Then, a microwave plasma-enhanced chemical vapor deposition (PECVD) system was used to grow CNWs on the interlayer-coated glass substrates by using a mixture of H2 and CH4 gases. The FE-SEM analysis of the cross-sectional and planar images confirmed that the thickness of interlayers linearly increased according to the deposition time. Furthermore, CNWs grown on the Ni interlayer were taller and denser than those grown on the Ti interlayer. Hall measurement applied to measure sheet resistance and conductivity confirmed that the electrical efficiency improved significantly as the Ni or Ti interlayers were used. Additionally, UV-Vis spectroscopy was also used to analyze the variations in light transmittance; CNWs synthesized on Ni-coated glass have lower average transmittance than those synthesized on Ti-coated glass. Based on this experiment, it was found that the direct growth of CNW was possible on the metal layer and the CNWs synthesized on Ni interlayers showed outstanding structural and electrical characterizations than the remaining interlayer type.

Preparation of Carbon Nanowall and Carbon Nanotube for Anode Material of Lithium-Ion Battery.

Carbon nanowall (CNW) and carbon nanotube (CNT) were prepared as anode materials of lithium-ion batteries. To fabricate a lithium-ion battery, copper (Cu) foil was cleaned using an ultrasonic cleaner in a solvent such as trichloroethylene (TCE) and used as a substrate. CNW and CNT were synthesized on Cu foil using plasma-enhanced chemical vapor deposition (PECVD) and water dispersion, respectively. CNW and CNT were used as anode materials for the lithium-ion battery, while lithium hexafluorophosphate (LiPF6) was used as an electrolyte to fabricate another lithium-ion battery. For the structural analysis of CNW and CNT, field emission scanning electron microscope (FE-SEM) and Raman spectroscopy analysis were performed. The Raman analysis showed that the carbon nanotube in composite material can compensate for the defects of the carbon nanowall. Cyclic voltammetry (CV) was employed for the electrochemical properties of lithium-ion batteries, fabricated by CNW and CNT, respectively. The specific capacity of CNW and CNT were calculated as 62.4 mAh/g and 49.54 mAh/g. The composite material with CNW and CNT having a specific capacity measured at 64.94 mAh/g, delivered the optimal performance.

Functional Coating to Improve the Anti-Pollution Characteristics for the Cover Glass of Photovoltaic Module.

A functional coating designed to prevent pollution was investigated on the surfaces of cover glass substrates for a photovoltaic (PV) module to improve the cover glass's anti-pollution characteristics. To identify the characteristics that can prevent pollution as well as the change in the contact angle of the thin film on the cover glass surface, three field-applicable coating methods were applied, and the coatings were annealed in two different annealing steps using a furnace. Step 1 refers to the annealing treatment of the coated films at 200 °C while step 2 refers to the second annealing treatment at 200, 300, and 400 °C. The anti-pollution characteristics, contact angle, transmittance, hardness, and adhesion were measured, and the results were analyzed. It was confirmed that the contact angle and the anti-pollution characteristics were better when the coated substrate was annealed twice at 200 °C than when it was annealed only once.

Improvement of Electrical Properties of Carbon Nanowall by the Deposition of Thin Film.

In this study, the improvement of the electrical properties of carbon nanowalls (CNWs) by the deposition of nonmetallic thin films such as carbon (C), silicon (Si), and silicon carbide (SiC) was investigated. The CNWs were synthesized on a Si wafer substrate using microwave-plasma-enhanced chemical vapor deposition (PECVD). The thin films were deposited through RF magnetron sputtering with a 4-inch target (C, Si, and Sic) on the grown CNWs. The surficial and cross-sectional conditions were examined using the images obtained from a field emission scanning electron microscope (FESEM). The structural characteristics were analyzed through Raman analysis. The analysis of the electric characteristics confirmed that the resistivity decreased for the nonmetallic-thin-film-coated samples, and that the mobility increased in the order of the as-deposited sample and the C-, SiC-, and Si-thin film-deposited samples. It was also confirmed that the deposition of the SiC thin films resulted in the lowest resistivity at 13.6 × 10-3 Ωcm, and that the deposition of the Si thin films showed the highest mobility at 304 cm2/VS.

Structural and Electrical Characteristics of Carbon Nanowalls Synthesized on the Polyimide Film.

In this study, the structural and electrical characteristics of carbon nanowalls (CNWs) synthesized on polyimide films were investigated. CNWs were synthesized on polyimide films as various growth times. The cross-section and surface of the CNWs synthesized were examined using FE-SEM. The growth and defects of CNWs were observed by raman spectrum. The hall measurement system was used to analyzed sheet resistance, resistivity and conductivity. The CNWs synthesized at 40 minutes showed outstanding structural and electrical characterizations than another growth times.

Development and Performance Analysis of Carbon Nanowall-Based Mass Sensor.

In this study, a mass sensor was fabricated using a carbon nanowalls, and its performance was analyzed. The substrate that was used to fabricate the mass sensor was a polyimide film, on which a SiO2 insulating layer and a copper electrode were deposited using an RF magnetron sputter. Thereafter, a carbon nanowalls was grown on the substrate until its size was 5 by 5 mm. The growth times of the completely grown carbon nanowalls were 20, 25, and 30 minutes, respectively. The performance of the mass sensors fabricated based on different carbon nanowalls grown for various growth times was analyzed according to the changing mass from 1 to 5 mg.

Pseudoangiomatous Stromal Hyperplasia of the Breast in a Female Adolescent Presenting as Bilateral Gigantomastia.

Pseudoangiomatous stromal hyperplasia (PASH) is a rare idiopathic proliferative mesenchymal breast disease related to hormonal imbalance, and thus extremely rare in children and adolescents. In addition, PASH manifests as a bilateral gigantomastia in some cases with no established cause or treatment. Here, we report a case of a rapidly developed PASH presenting with bilateral gigantomastia in a 14-year-old premenarchial female patient. Considering the patient's age and emotions and the need for nipple-areolar complex repositioning, we performed reduction mammoplasty rather than total mastectomy despite the possibility of recurrence. Although some masses could not be completely removed, no complications, such as infection, wound dehiscence, or hematoma occurred postoperatively. The patient was stable during the 18-month follow-up period, although an evidence of recurrent and residual disease was noted upon ultrasonography.

Innovative Variation in the Morphological Characteristics of Carbon Nanowalls Grown on a Molybdenum Disulfide Interlayer.

Carbon is a material with interesting properties which exists in large quantities on Earth, so many studies involving carbon have been conducted. In particular, nano-sized carbon allotropes, referred to as carbon nanomaterials, comprise the subject of various studies currently underway. The electrical, chemical, physical properties of carbon nanowalls (CNWs) are modified by parameters such as surface density, height and thickness. These characteristics have significant effects on CNWs and can be adjusted as a growth interlayer. It was confirmed that the molybdenum disulfide (MoS2) interlayer synthesized in this paper by radio frequency (RF) magnetron sputtering altered the morphological characteristics of the CNWs, including its shaped edge, pores diameter and density. We provide interesting results through FE-SEM, EDS and Raman analysis in this paper. Based on the Raman analysis, both the D-peak of carbon and the ID/IG ratio decreased. Through this study, the effect of MoS2 on the morphological characteristics of CNWs was confirmed.

Enhanced Electrochemical Properties of Non-stoichiometric Layered Perovskites, Sm1-xBaCo2O5+d, for IT-SOFC Cathodes.

In this study, electrochemical properties of layered perovskites having non-stoichiometric compositions (Sm1-xBaCo2O5+d, x = 0, 0. 01, 0.02, 0.03, 0.04, 0.05, 0.10, and 0.15) were analyzed for the direct application of cathode materials for Intermediate Temperature-operating Solid Oxide Fuel Cells (IT-SOFC). From the Sm1-xBaCo2O5+d oxide systems calcined at 1,100°C for 8 h, single phase (SmBaCo2O5+d, SBCO_1) was maintained only in the case of the x = 0 composition. In the compositions of x = 0.05-0.10, BaCoO2.6 was mixed with the pattern of SBCO. In addition, in the composition of x = 0.15, it was confirmed that BaCoO2.6 and CoO phases coexisted with SBCO. In the compositions of Sm1-xBaCo2O5+d, the overall Area Specific Resistance (ASR) values decreased as the removal amount of Sm increased from x = 0-0.10; then, the values increased for compositions from x = 0.15. For example, the ASRs of SBCO_1, Sm0.95BaCo2O5+d (SBCO_0.95), Sm0.90BaCo2O5+d (SBCO_0.90), and Sm0.85BaCo2O5+d (SBCO_0.85) measured at 600°C were 0.301, 0.147, 0.119, and 0.179 Ω cm2, respectively. In particular, SBCO_0.90 was found to have an excellent ASR property of about 0.035 Ω cm2 at 700°C. Typical properties of the metal-insulator transition (MIT) electrical conductivity were shown in all measured compositions. The temperature at which MIT occurred increased as the non-stoichiometric composition increased.

Analysis of plasma-grown carbon oxide and reduced-carbon-oxide nanowalls.

In this study, several characteristics of carbon oxide nanowalls (CONWs) and reduced-carbon-oxide nanowalls (rCONWs) activated using plasma and thermochemistry were investigated. To become modified CONW and rCONW, catalyst-free carbon nanowalls (CNWs) were grown on a silicon (Si) wafer via microwave-plasma-enhanced chemical vapor deposition (MPECVD) with a mixture of hydrogen (H2) and methane (CH4) gases. The CONW was modified by oxidizing a CNW on a Si wafer with plasma treatment using oxygen (O2) plasma. Afterwards, the CONW was placed in a rapid-thermal-annealing (RTA) chamber, and H2 gas was injected thereto; therefore, the CONW was reduced by H2 gas. The surface properties of the CONW and rCONW were confirmed via scanning electron microscopy (SEM). Raman spectroscopy was used for structural analysis, and the surface energy of each surface was analyzed by operating the contact angle. The chemical characteristics were observed via X-ray photoelectron spectroscopy (XPS). Hall measurements were applied to investigate the electrical characteristics.

Growing Properties of Carbon Nanowalls According to the Hydrogen Gas Ratio.

In this study, the growth characteristics of carbon nanowalls (CNWs), which are applied to many devices because of their high aspect ratio and excellent electrical characteristics thanks to their two-dimensional structure, were confirmed by changing the ratio of methane (CH4) and hydrogen (H2) therein. In many studies, CNWs were grown using various chemical vapor deposition (CVD) or sputtering methods, with a mixture of CH4 and H2 or argon (Ar) gas. To find the suitable rate, 25 sccm CH4, which is used as the source gas, was first injected into the chamber, and the characteristics were confirmed by changing the amount of H2 gas from 0 to 50 sccm. Ultrasonically cleaned Si wafer was used as the substrate, and the CNW was grown for 10 minutes at microwave power (1300 W, 600°C) using microwave-plasma-enhanced CVD (MPECVD).

Innovative Method Using Adhesive Force for Surface Micromachining of Carbon Nanowall.

 The application of a carbon nanowall (CNW) via transfer is very demanding due to the unusual structure of vertically grown wall-shaped that easily collapses. In addition, direct growth on a device cannot obtain a precision-patterned shape because of the temperature limit of the photoresist (PR). Therefore, in this paper, we demonstrate a new CNW surface micromachining technology capable of direct growth. In order to reduce unexpected damage caused by chemical etching, a physical force was used to etch with the adhesive properties of CNWs that have low adhesion to silicon wafer. To prevent compositing with PR, the CNW was surface modified using oxygen plasma. Since there is a risk of surface-modified CNW (SMCNW) collapse in an ultrasonic treatment, which is a physical force, the CNW was coated with PR. After etching the SMCNW grown on PR uncoated area, PR was lifted off using an acetone solution. The effect on the SMCNW by the lift-off process was investigated. The surface, chemical, and structural properties of PR-removed SMCNW and pristine-SMCNW were compared and showed a minimal difference. Therefore, the CNW surface micromachining technique was considered successful.

SmBa1-xCaxCo2O5+d Layered Perovskite Cathodes for Intermediate Temperature-operating Solid Oxide Fuel Cells.

In SmBa1-xCaxCo2O5+d (x = 0.01, 0.03, 0.1, and 0.2, SBCCO) oxide systems calcined at 1100°C for 8 h, the XRD patterns of the SBCCO single phase were maintained in the cases of SmBa0.97Ca0.03Co2O5+d (SBCCO-0.97) and SmBa0.99Ca0.01Co2O5+d (SBCCO-0.99) compositions. In SmBa0.8Ca0.2Co2O5+d (SBCCO-0.8) and SmBa0.9Ca0.1Co2O5+d (SBCCO-0.9), CaCoSmO4 existed with the pattern SBCCO. SBCCO structures were identified as orthorhombic crystal structures because they showed splitting of the X-ray diffraction (XRD) peaks at 23.4°, 47.9°, and 59.1°.Typical metallic conduction behaviors were found in all measured compositions except SBCCO-0.8, which showed a metal-insulator transition (MIT) behavior. Compared to other SmBa1-xCaxCo2O5+d compositions, SBCCO-0.8 showed the highest electrical conductivity of 460 S/cm at 500°C. In particular, SBCCO-0.9 was found to have an excellent ASR characteristic of about 0.077 Ωcm2 at 700°C. The activation energy of SBCCO-0.9 was the lowest among SBCCO oxide systems with a value of 0.77 eV.

Influence of Deposition Pressure on the Properties of Round Pyramid Textured a-Si:H Solar Cells for Maglev.

HIT (Heterojunction with Intrinsic Thin-layer) photovoltaic cells is one of the highest efficiencies in the commercial solar cells. The pyramid texturization for reducing surface reflectance of HIT solar cells silicon wafers is widely used. For the low leakage current and high shunt of solar cells, the intrinsic amorphous silicon (a-Si:H) on substrate must be uniformly thick of pyramid structure. However, it is difficult to control the thickness in the traditional pyramid texturing process. Thus, we textured the intrinsic a-Si:H thin films with the round pyramidal structure by using HNO3, HF, and CH3COOH solution. The characteristics of round pyramid a-Si:H solar cells deposited at pressure of 500, 1000, 1500, and 2000 mTorr by PECVD (Plasma Enhanced Chemical Vapor Deposition) was investigated. The lifetime, open circuit voltage, fill factor and efficiency of a-Si:H solar cells were investigated with respect to various deposition pressure.

Effects of Plasma Treatment on Carbon Nanowalls Grown by Microwave Plasma Enhanced Chemical Vapor Deposition.

In this study, the effects of post-plasma treatment on synthesized carbon nanowalls (CNWs) grown with a microwave were investigated. CNWs were synthesized by microwave plasma enhanced chemical vapor deposition (PECVD), employing a mixture of CH4 and H2 gases. The plasma treatment was done in different plasma environments (O2 and H2) but under the same condition of synthesized CNWs. Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), and fourier transform infrared spectroscopy (FT-IR) were used to analyze the effects of the post-plasma treatment on the synthesized CNWs. After the H2 post-plasma treatment, no significant changes in the appearance and characteristics of the CNWs were observed. After the O2 post-plasma treatment, on the other hand, the CNWs were etched at a rate of 18.05 nm/sec. The Raman analysis confirmed, however, that the structural changes in the CNWs caused by the O2 post-plasma treatment were insignificant.

Influence of Oxygen Gas Ratio on the Properties of Aluminum-Doped Zinc Oxide Films Prepared by Radio Frequency Magnetron Sputtering.

Aluminum-doped zinc oxide (AZO) thin films were deposited on glass and polyimide substrates using radio frequency magnetron sputtering. We investigated the effects of the oxygen gas ratio on the properties of the AZO films for Cu(In,Ga)Se2 thin-film solar cell applications. The structural and optical properties of the AZO thin films were measured using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and UV-Visible-NIR spectrophotometry. The oxygen gas ratio played a crucial role in controlling the optical as well as electrical properties of the films. When oxygen gas was added into the film, the surface AZO thin films became smoother and the grains were enlarged while the preferred orientation changed from (0 0 2) to (1 0 0) plane direction of the hexagonal phase. An improvement in the transmittance of the AZO thin films was achieved with the addition of 2.5-% oxygen gas. The electrical resistivity was highly increased even for a small amount of the oxygen gas addition.