간행물
한국재료학회지 KCI 등재 SCOPUS Korean Journal of Materials Research
- 발행기관 한국재료학회
- 자료유형 학술지
- 간기 월간
- ISSN 2799-8525 (Print)2799-8681 (Online)
- 수록기간 1991 ~ 2024
- 주제분류 공학 > 재료공학 공학 분류의 다른 간행물
- 십진분류KDC 530DDC 620
권호리스트/논문검색
제20권 제12호 (2010년 12월) 12건
1.
2010.12
구독 인증기관 무료, 개인회원 유료
Abstract In this study characteristics of Al-doped ZnO thin film by HIPIMS (High power impulse sputtering) are discussed. Deposition speed of HIPIMS with conventional balanced magnetic field is measured at about 3 nm/min, which is 30% of that of conventional RF sputtering process with the same working pressure. To generate additional magnetic flux and increase sputtering speed, electromagnetic coil is mounted at the back side of target. Under unbalanced magnetic flux from electromagnet with 1.5A coil current, deposition speed of AZO thin film is increased from 3 nm/min to 4.4 nm/min. This new value originates from the decline of particles near target surface due to the local magnetic flux going toward substrate from electromagnet. AZO film sputtered by HIPIMS process shows very smooth and dense film surface for which surface roughness is measured from 0.4 nm to 1 nm. There are no voids or defects in morphology of AZO films with varying of magnetic field. When coil current is increased from 0A to 1A, transmittance of AZO thin film decreases from 80% to 77%. Specific resistance is measured at about 2.9×10-2Ω·cm. AZO film shows C-axis oriented structure and its grain size is calculated at about 5.3 nm, which is lower than grain size in conventional sputtering.
4,000원
2.
2010.12
구독 인증기관 무료, 개인회원 유료
ZnO thin films were prepared on a glass substrate by radio frequency (RF) magnetron sputtering without intentional substrate heating and then surfaces of the ZnO films were irradiated with intense electrons in vacuum condition to investigate the effect of electron bombardment on crystallization, surface roughness, morphology and hydrogen gas sensitivity. In XRD pattern, as deposited ZnO films show a higher ZnO (002) peak intensity. However, the peak intensity for ZnO (002) is decreased with increase of electron bombarding energy. Atomic force microscope images show that surface morphology is also dependent on electron bombarding energy. The surface roughness increases due to intense electron bombardment as high as 2.7 nm. The observed optical transmittance means that the films irradiated with intense electron beams at 900 eV show lower transmittance than the others due to their rough surfaces. In addition, ZnO films irradiated by the electron beam at 900 eV show higher hydrogen gas sensitivity than the films that were electron beam irradiated at 450 eV. From XRD pattern and atomic force microscope observations, it is supposed that intense electron bombardment promotes a rough surface due to the intense bombardments and increased gas sensitivity of ZnO films for hydrogen gas. These results suggest that ZnO films irradiated with intense electron beams are promising for practical high performance hydrogen gas sensors.
3,000원
3.
2010.12
구독 인증기관 무료, 개인회원 유료
Information technology devices, such as cellular phones, MP3s and so on, due to restrictions of space, require thin and small micro-speakers to generate sound. The reduction of the size of micro-speakers has resulted in the decrease of sound quality, due to such factors as frequency range and sound pressure level. In this study, the acoustical properties of oval microspeakers has been studied as a function of pattern shape on the diaphragm. The other conditions of micro-speakers, except for the pattern, was not changed. When the pattern is present on the diaphragm and the shape of pattern was a whirlwind, the resonance frequency was reduced due to the decrease of tensile strength of diaphragm. The patterns presented in the semi-minor axis of diaphragm did not effect a change of resonance frequency. However, increasing the number of patterns in the semimajor axis of diaphragm became a reason for the decrease of resonance frequency on edge side. When the depth of pattern on edge side was increased, the resonance frequency was decreased due to reduction of geometrical stiffness. If the height of edge and dome were increased, the resonance frequency and geometrical stiffness rapidly increased. After reaching the maximum values, they began to decrease with the continuous increase of height.
4,000원
4.
2010.12
구독 인증기관 무료, 개인회원 유료
The structure and morphology of epitaxial layer defects in epitaxial Si wafers produced by the Czochralski methodwere studied using focused ion beam (FIB) milling, scanning electron microscopy (SEM), and transmission electron microscopy(TEM). Epitaxial growth was carried out in a horizontal reactor at atmospheric pressure. The p-type Si wafers were loaded intothe reactor at about 800oC and heated to about 1150oC in H2. An epitaxial layer with a thickness of 4µm was grown at atemperature of 1080-1100oC. Octahedral void defects, the inner walls of which were covered with a 2-4nm-thick oxide, weresurrounded mainly by 111 planes. The formation of octahedral void defects was closely related to the agglomeration ofvacancies during the growth process. Cross-sectional TEM observation suggests that the carbon impurities might possibly berelated to the formation of oxide defects, considering that some kinds of carbon impurities remain on the Si surface duringoxidation. In addition, carbon and oxygen impurities might play a crucial role in the formation of void defects during growthof the epitaxial layer.
3,000원
5.
2010.12
구독 인증기관 무료, 개인회원 유료
In this paper, double texturization of multi crystalline silicon solar cells was studied with laser and reactive ion etching (RIE). In the case of multi crystalline silicon wafers, chemical etching has problems in producing a uniform surface texture. Thus various etching methods such as laser and dry texturization have been studied for multi crystalline silicon wafers. In this study, laser texturization with an Nd:YVO4 green laser was performed first to get the proper hole spacing and 300μm was found to be the most proper value. Laser texturization on crystalline silicon wafers was followed by damage removal in acid solution and RIE to achieve double texturization. This study showed that double texturization on multi crystalline silicon wafers with laser firing and RIE resulted in lower reflectance, higher quantum yield and better efficiency than that process without RIE. However, RIE formed sharp structures on the silicon wafer surfaces, which resulted in 0.8% decrease of fill factor at solar cell characterization. While chemical etching makes it difficult to obtain a uniform surface texture for multi crystalline silicon solar cells, the process of double texturization with laser and RIE yields a uniform surface structure, diminished reflectance, and improved efficiency. This finding lays the foundation for the study of low-cost, high efficiency multi crystalline silicon solar cells.
4,000원
6.
2010.12
구독 인증기관 무료, 개인회원 유료
The influences of Na and K content on the crystal phase, the microstructure and the electrical property of BaTiO3-based thermistors was found to show typical PTC effects. The crystal phase of powder calcined at 1000˚C for 4hrs showed a single phase with BaTiO3, and the crystal structure was transformed from tetragonal to cubic phase according to added amounts of Na and K. In XRD results at 43˚~47˚, the (Ba0.858Na0.071K0.071)(Ti0.9985Nb0.0015)O3-δ showed (002) and (200) peaks but the (Ba0.762Na0.119K0.119)(Ti0.9975Nb0.0025)O3-δ showed (002), (020) and (200) peaks. In sintered bodies, those calcined at 600˚C rather than at 1000˚C were dense, and for certain amounts of Na and K showed rapid decreases in grain size. In relative permittivity, the curie temperature due to the transformation of ferroelectric phase rose with added Na and K but decreased in terms of relative permittivity. In the result of the R-T curve, the sintered bodies have curie temperatures of about 140˚C and the resistivity of sintered bodies have scores of Ω·cm; the jump order of sintered bodies was shown to be more than 104 in powder calcined at 1000˚C.
4,000원
7.
2010.12
구독 인증기관 무료, 개인회원 유료
Cu(In,Ga)Se2(CIGS) photovoltaic thin films were electrodeposited on Mo/glass substrates with an aqueous solution containing 2 mM CuCl2, 8 mM InCl3, 20 mM GaCl3 and 8mM H2SeO3 at the electrodeposition potential of -0.6 to -1.0 V(SCE) and pH of 1.8. The best chemical composition of Cu1.05In0.8Ga0.13Se2 was found to be achieved at -0.7 V(SCE). The precursor Cu-In-Ga-Se films were annealed for crystallization to chalcopyrite structure at temperatures of 100-500˚C under Ar gas atmosphere. The chemical compositions, microstructures, surface morphologies, and crystallographic structures of the annealed films were analyzed by EPMA, FE-SEM, AFM, and XRD, respectively. The precursor Cu-In-Ga-Se grains were grown sparsely on the Mo-back contact and also had very rough surfaces. However, after annealing treatment beginning at 200˚C, the empty spaces between grains were removed and the grains showed well developed columnar shapes with smooth surfaces. The precursor Cu-In-Ga-Se films were also annealed at the temperature of 500˚C for 60 min under Se gas atmosphere to suppress the Se volatilization. The Se amount on the CIGS film after selenization annealing increased above the Se amount of the electrodeposited state and the MoSe2 phase occurred, resulting from the diffusion of Se through the CIGS film and interaction with Mo back electrode. However, the selenization-annealed films showed higher crystallinity values than did the films annealed under Ar atmosphere with a chemical composition closer to that of the electrodeposited state.
4,000원
8.
2010.12
구독 인증기관 무료, 개인회원 유료
One of the greatest challenges for our society is providing powerful electrochemical energy conversion and storage devices. Rechargeable lithium-ion batteries and fuel cells are among the most promising candidates in terms of energy and power density. As the starting material, TiCl4·YCl3 solution and dispersing agent (HCP) were mixed and synthesized using ammonia as the precipitation agent, in order to prepare the nano size Y doped spherical TiO2 precursor. Then, the Li4Ti5O12 was synthesized using solid state reaction method through the stoichiometric mixture of Y doped spherical TiO2 precursor and LiOH. The Ti mole increased the concentration of the spherical particle size due to the addition of HPC with a similar particle size distribution in a well in which Li4Ti5O12 spherical particles could be obtained. The optimal synthesis conditions and the molar ratio of the Ti 0.05 mol reaction at 50˚C for 30 minutes and at 850˚C for 6 hours heat treatment time were optimized. Li4Ti5O12 was prepared by the above conditions as a working electrode after generating the Coin cell; then, electrochemical properties were evaluated when the voltage range of 1.5V was flat, the initial capacity was 141 mAh/g, and cycle retention rate was 86%; also, redox reactions between 1.5 and 1.7V, which arose from the insertion and deintercalation of 0.005 mole of Y doping is not a case of doping because the C-rate characteristics were significantly better.
4,000원
9.
2010.12
구독 인증기관 무료, 개인회원 유료
Most TCOs such as ITO, AZO(Al-doped ZnO), FTO(F-doped SnO2) etc., which have been widely used in LCD,touch panel, solar cell, and organic LEDs etc. as transparent electrode material reveal n-type conductivity. But in order to realizetransparent circuit, transparent p-n junction, and introduction of transparent p-type materials are prerequisite. Additionalprerequisite condition is optical transparency in visible spectral region. Oxide based materials usually have a wide optical band-gap more than ~3.0eV. In this study, single-phase transparent semiconductor of SrCu2O2, which shows p-type conductivity, havebeen synthesized by 2-step solid state reaction at 950oC under N2 atmosphere, and single-phase SrCu2O2 thin films of p-typeTCOs have been deposited by RF magnetron sputtering on alkali-free glass substrate from single-phase target at 500oC, 1%H2/(Ar+H2) atmosphere. 3% H2/(Ar+H2) resulted in formation of second phases. Hall measurements confirmed the p-typenature of the fabricated SrCu2O2 thin films. The electrical conductivity, mobility of carrier and carrier density 5.27×10−2S/cm,2.2cm2/Vs, 1.53×1017/cm3 a room temperature, respectively. Transmittance and optical band-gap of the SrCu2O2 thin filmsrevealed 62% at 550nm and 3.28eV. The electrical and optical properties of the obtained SrCu2O2 thin films deposited by RFmagnetron sputtering were compared with those deposited by PLD and e-beam.
4,000원
10.
2010.12
구독 인증기관 무료, 개인회원 유료
The application of flip chip technology has been growing with the trend of miniaturization of electronic packages, especially in mobile electronics. Currently, several types of adhesive are used for flip chip bonding and these adhesives require some special properties; they must be solvent-free and fast curing and must ensure joint reliability against thermal fatigue and humidity. In this study, imidazole and its derivatives were added as curing catalysts to epoxy resin and their effects on the adhesive properties were investigated. Non-isothermal DSC analyses showed that the curing temperatures and the heat of reaction were dependent primarily on the type of catalyst. Isothermal dielectric analyses showed that the curing time was dependent on the amount of catalysts added as well as their type. The die shear strength increased with the increase of catalyst content while the Tg decreased. From this study, imidazole catalysts with low molecular weight are expected to be beneficial for snap curing and high adhesion strength for flip chip bonding applications.
4,000원
11.
2010.12
구독 인증기관 무료, 개인회원 유료
TiO2 nanowires were self-catalytically synthesized on bare Si(100) substrates using metallorganic chemical vapor deposition. The nanowire formation was critically affected by growth temperature. The TiO2 nanowires were grown at a high density on Si(100) at 510˚C, which is near the complete decomposition temperature (527˚C) of the Ti precursor (Ti(O-iPr)2(dpm)2). At 470˚C, only very thin (< 0.1μm) TiO2 film was formed because the Ti precursor was not completely decomposed. When growth temperature was increased to 550˚C and 670˚C, the nanowire formation was also significantly suppressed. A vaporsolid (V-S) growth mechanism excluding a liquid phase appeared to control the nanowire formation. The TiO2 nanowire growth seemed to be activated by carbon, which was supplied by decomposition of the Ti precursor. The TiO2 nanowire density was increased with increased growth pressure in the range of 1.2 to 10 torr. In addition, the nanowire formation was enhanced by using Au and Pt catalysts, which seem to act as catalysts for oxidation. The nanowires consisted of well-aligned ~20-30 nm size rutile and anatase nanocrystallines. This MOCVD synthesis technique is unique and efficient to self-catalytically grow TiO2 nanowires, which hold significant promise for various photocatalysis and solar cell applications.
4,000원
12.
2010.12
구독 인증기관 무료, 개인회원 유료
Magnesium hydroxide-melamine core-shell particles were prepared through the coating of melamine monomer on the surface of magnesium hydroxide in the presence of phosphoric acid. The melamine monomer was dissolved in hot water but recrystallized on the surface of magnesium hydroxide by quenching to room temperature in the presence of phosphoric acid. The core-shell particle was applied to low-density polyethylene/ ethylene vinyl acetate (LDPE/EVA) resin by melt-compounding at 180˚C as flame retardant. The effect of magnesium hydroxide and melamine content has been studied on the flame retardancy of the core-shell particles in LDPE/EVA resin according to the preparation process and purity of magnesium hydroxide. Magnesium hydroxide prepared with sodium hydroxide rather than with ammonia solution revealed higher flame retardancy in core-shell particles with LDPE/EVA resin. At 50 wt% loading of flame retardant, core-shell particles revealed higher flame retardancy compared to that of the exclusive magnesium hydroxide in LDPE/EVA composite, and it was possible to satisfy the V0 grade in the UL-94 vertical test. The synergistic flame retardant effect of magnesium hydroxide and melamine core-shell particles was explained as being due to the endothermic decomposition of magnesium hydroxide and melamine, which was followed by the evolution of water from the magnesium hydroxide and porous char formation due to reactive nitrogen compounds, and carbon dioxide generated from melamine.
4,000원
