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
제18권 제4호 (2008년 4월) 10건
1.
2008.04
구독 인증기관 무료, 개인회원 유료
The structural and electrical properties of amorphous BaSm2Ti4O12 (BSmT) films on a TiN/SiO2/Si substrate deposited using a RF magnetron sputtering method were investigated. The deposition of BSmT films was carried out at 300˚C in a mixed oxygen and argon (O2 : Ar = 1 : 4) atmosphere with a total pressure of 8.0 mTorr. In particular, a 45 nm-thick amorphous BSmT film exhibited a high capacitance density and low dissipation factor of 7.60 fF/μm2 and 1.3%, respectively, with a dielectric constant of 38 at 100 kHz. Its capacitance showed very little change, even in GHz ranges from 1.0 GHz to 6.0 GHz. The quality factor of the BSmT film was as high as 67 at 6 GHz. The leakage current density of the BSmT film was also very low, at approximately 5.11 nA/cm2 at 2 V; its conduction mechanism was explained by the the Poole-Frenkel emission. The quadratic voltage coefficient of capacitance of the BSmT film was approximately 698 ppm/V2, which is higher than the required value (<100 ppm/V2) for RF application. This could be reduced by improving the process condition. The temperature coefficient of capacitance of the film was low at nearly 296 ppm/˚C at 100 kHz. Therefore, amorphous BSmT grown on a TiN substrate is a viable candidate material for a metal-insulator-metal capacitor.
4,000원
2.
2008.04
구독 인증기관 무료, 개인회원 유료
In this study, the thermoelectric power and resistivity of the perovskite manganiteLa0.75Ba0.25MnO3 were investigated in the temperature range 300K-1200K. The electrical resistivity andthermoelectric power indicate a transport mechanism dominated by adiabatic small-polaron hopping. Thepower factor increases from 2×10−6W/mK2 to 1×10−5W/mK2 as to the temperature increases from 400K to1200K, which indicates that the compound is highly feasible as a thermoelectric material at high temperatures.
4,000원
3.
2008.04
구독 인증기관 무료, 개인회원 유료
In this study, tantalum (Ta) compacts were fabricated in a spark plasma sintering (SPS) process and their microstructure and mechanical properties were investigated. Ta compacts with a density of 99% were successfully fabricated by controlling the sintering conditions of the current and the temperature. The density and hardness were increased as the sintering temperature increased. The Ta2C compound was observed at the surface of the compacts due to the contact between the Ta powder and graphite mold during the sintering process. The main fracture mode showed a mixed type with intergranular and transgranular modes having some roughness.
4,000원
4.
2008.04
구독 인증기관 무료, 개인회원 유료
Multi-walled carbon nanotube (MWNT)/SnO2 nano-composite (MSC) for the anode electrode of a Li-ion battery was prepared using a homogeneous precipitation method with SnCl2 precursors in the presence of MWNT. XRD results indicate that when annealed in Ar at 400˚C, Sn6O4(OH)4 was fully converted to SnO2 phases. TEM observations showed that most of the SnO2 nanoparticles were deposited directly on the outside surface of the MWNT. The electrochemical performance of the MSC electrode showed higher specific capacities than a MWNT and better cycleability than a nano-SnO2 electrode. The electrochemical performance of the MSC electrode improved because the MWNT in the MSC electrode absorbed the mechanical stress induced from a volume change during alloying and de-alloying reactions with lithium, leading to an increase in the electrical conductivity of the composite material.
4,000원
5.
2008.04
구독 인증기관 무료, 개인회원 유료
WO3-doped SnO2 thin films were prepared in a solution-deposition method and their gas-sensing characteristics were investigated. The doping of WO3 to SnO2 increased the response (Ra/Rg, Ra: resistance in air, Rg: resistance in gas) to H2 substantially. Moreover, the Ra/Rg value of 10 ppm CO increased to 5.65, whereas that of NO2 did not change by a significant amount. The enhanced response to H2 and the selective detection of CO in the presence of NO2 were explained in relation to the change in the surface reaction by the addition of WO3. The WO3-doped SnO2 sensor can be used with the application of a H2 sensor for vehicles that utilize fuel cells and as an air quality sensor to detect CO-containing exhaust gases emitted from gasoline engines.
4,000원
6.
2008.04
구독 인증기관 무료, 개인회원 유료
High-efficiency phosphorescent organic light emitting diodes using TCTA-TAZ as a double host and Ir(ppy)3 as a dopant were fabricated and their electro-luminescence properties were evaluated. The fabricated devices have the multi-layered organic structure of 2-TNATA/NPB/(TCTA-TAZ) : Ir(ppy)3/BCP/SFC137 between an anode of ITO and a cathode of LiF/AL. In the device structure, 2-TNATA[4,4',4"-tris(2-naphthylphenyl-phenylamino)-triphenylamine] and NPB[N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine] were used as a hole injection layer and a hole transport layer, respectively. BCP [2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline] was introduced as a hole blocking layer and an electron transport layer, respectively. TCTA [4,4',4"-tris(N-carbazolyl)-triphenylamine] and TAZ [3-phenyl-4-(1-naphthyl)-5-phenyl-1,2,4-triazole] were sequentially deposited, forming a double host doped with Ir(ppy)3 in the [TCTA-TAZ] : Ir(ppy)3 region. Among devices with different thickness combinations of TCTA (50 Å-200 Å) and TAZ (100 Å-250 Å) within the confines of the total host thickness of 300 Å and an Ir(ppy)3-doping concentration of 7%, the best electroluminescence characteristics were obtained in a device with 100 Å-think TCTA and 200 Å-thick TAZ. The Ir(ppy)3 concentration in the doping range of 4%-10% in devices with an emissive layer of [TCTA (100 Å)-TAZ (200 Å)] : Ir(ppy)3 gave rise to little difference in the luminance and current efficiency.
4,000원
7.
2008.04
구독 인증기관 무료, 개인회원 유료
1.5 μm-thick copper films deposited on silicon wafers were successfully bonded at 415˚C/25 kN for 40 minutes in a thermo-compression bonding method that did not involve a pre-cleaning or pre-annealing process. The original copper bonding interface disappeared and showed a homogeneous microstructure with few voids at the original bonding interface. Quantitative interfacial adhesion energies were greater than 10.4 J/m2 as measured via a four-point bending test. Post-bonding annealing at a temperature that was less than 300˚C had only a slight effect on the bonding energy, whereas an oxygen environment significantly deteriorated the bonding energy over 400˚C. This was most likely due to the fast growth of brittle interfacial oxides. Therefore, the annealing environment and temperature conditions greatly affect the interfacial bonding energy and reliability in Cu-Cu bonded wafer stacks.
4,000원
8.
2008.04
구독 인증기관 무료, 개인회원 유료
A ZrO2 coating solution containing ZrO2 photo-catalysis, which is transparent in visible light, was prepared by the hydrolysis of alkoxide, and thin films on the SiO2 glass substrate were formed in a dipcoating method. These thin films were heat-treated at temperatures ranging from 250˚C-800˚C and their characteristics were subjected to thermal analysis, XRD, spectrometry, SEM, EDS, contact angle measurement, and AFM. Tetragonal ZrO2 phase was found in the thin film heat treated at 450˚C, and anatase TiO2 phase was detected in the thin film heat-treated at 600˚C and above. The thickness of the films was approximately 300 nm, and the roughness was 0.66 nm. Thus, the film properties are excellent. The films are super hydrophilic with a contact angle of 4.0˚; moreover, they have self-cleaning effect due to the photo catalytic property of anatase TiO2.
4,000원
9.
2008.04
구독 인증기관 무료, 개인회원 유료
A Fe(OH)2 suspension was prepared by mixing iron sulfate and a weak alkali ammonia solution. Following this, iron oxides were synthesized by passing pure oxygen through the suspension (oxidation). The effects of different reaction temperatures (30˚C, 50˚C, 70˚C) and equivalent ratios (0.1~10.0) on the formation of iron oxides were investigated. An equilibrium phase diagram was established by quantitative phase analysis of the iron oxides using the Rietveld method. The equilibrium phase diagram showed a large difference from the equilibrium phase diagram of Kiyama when the equivalent ratio was above 1, and single Fe3O4 phase only formed above an equivalent ratio 2 at all reaction temperatures. Kiyama synthesized iron oxide using iron sulfate and a strong alkali NaOH solution.
3,000원
10.
2008.04
구독 인증기관 무료, 개인회원 유료
In this study, BaTiO3 thin films were grown by RF-magnetron sputtering, and the effects of a post-annealing process on the structural characteristics of the BaTiO3 thin films were investigated. For the crystallization of the grown thin films, post-annealing was carried out in air at an annealing temperature that varied from 500-1000˚C. XRD results showed that the highest crystal quality was obtained from the samples annealed at 600-700˚C. From the SEM analysis, no crystal grains were observed after annealing at temperatures ranging from 500 to 600˚C; and 80 nm grains were obtained at 700˚C. The surface roughness of the BaTiO3 thin films from AFM measurements and the crystal quality from Raman analysis also showed that the optimum annealing temperature was 700˚C. XPS results demonstrated that the binding energy of each element of the thin-film-type BaTiO3 in this study shifted with the annealing temperature. Additionally, a Ti-rich phenomenon was observed for samples annealed at 1000˚C. Depth-profiling analysis through a GDS (glow discharge spectrometer) showed that a stoichiometric composition could be obtained when the annealing temperature was in the range of 500 to 700˚C. All of the results obtained in this study clearly demonstrate that an annealing temperature of 700˚C results in optimal structural properties of BaTiO3 thin films in terms of their crystal quality, surface roughness, and composition.
4,000원
