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 제5호 (2010년 5월) 9건
1.
2010.05
구독 인증기관 무료, 개인회원 유료
We investigated the carbon monoxide (CO) gas-sensing properties of nanostructured Al-doped zinc oxide thin films deposited on self-assembled Au nanodots (ZnO/Au thin films). The Al-doped ZnO thin film was deposited onto the structure by rf sputtering, resulting in a gas-sensing element comprising a ZnO-based active layer with an embedded Pt/Ti electrode covered by the self-assembled Au nanodots. Prior to the growth of the active ZnO layer, the Au nanodots were formed via annealing a thin Au layer with a thickness of 2 nm at a moderate temperature of 500˚C. It was found that the ZnO/Au nanostructured thin film gas sensors showed a high maximum sensitivity to CO gas at 250˚C and a low CO detection limit of 5 ppm in dry air. Furthermore, the ZnO/Au thin film CO gas sensors exhibited fast response and recovery behaviors. The observed excellent CO gas-sensing properties of the nanostructured ZnO/Au thin films can be ascribed to the Au nanodots, acting as both a nucleation layer for the formation of the ZnO nanostructure and a catalyst in the CO surface reaction. These results suggest that the ZnO thin films deposited on self-assembled Au nanodots are promising for practical high-performance CO gas sensors.
4,000원
2.
2010.05
구독 인증기관 무료, 개인회원 유료
One of the weak points of the Cr-doped SZO is that until now, it has only been fabricated on perovskite substrates, whereas NiO-ReRAM devices have already been deposited on Si substrates. The fabrication of RAM devices on Si substrates is important for commercialization because conventional electronics are based mainly on silicon materials. Cr-doped ReRAM will find a wide range of applications in embedded systems or conventional memory device manufacturing processes if it can be fabricated on Si substrates. For application of the commercial memory device, Cr-doped SrZrO3 perovskite thin films were deposited on a SrRuO3 bottom electrode/Si(100)substrate using pulsed laser deposition. XRD peaks corresponding to the (112), (004) and (132) planes of both the SZO and SRO were observed with the highest intensity along the (112) direction. The positions of the SZO grains matched those of the SRO grains. A well-controlled interface between the SrZrO3:Cr perovskite and the SrRuO3 bottom electrode were fabricated, so that good resistive switching behavior was observed with an on/off ratio higher than 102. A pulse test showed the switching behavior of the Pt/SrZrO3:Cr/SrRuO3 device under a pulse of 10 kHz for 104 cycles. The resistive switching memory devices made of the Cr-doped SrZrO3 thin films deposited on Si substrates are expected to be more compatible with conventional Si-based electronics.
4,000원
3.
2010.05
구독 인증기관 무료, 개인회원 유료
The composite photocatalysts of a Fe-modified carbon nanotube (CNT)-TiO2 were synthesized by a two-step sol-gel method at high temperature. Its chemical composition and surface properties were investigated by BET surface area, scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray diffraction (XRD) and ultraviolet-visible (UV-Vis) spectroscopy. The results showed that the BET surface area was improved by modification of Fe, which was related to the adsorption capacity for each composite. Interesting thin layer aggregates of nanosized TiO2 were observed from TEM images, probably stabilized by the presence of CNT, and the surface and structural characterization of the samples was carried out. The XRD results showed that the Fe/CNT-TiO2 composites contained a mix of anatase and rutile forms of TiO2 particles when the precursor is TiOSO4·xH2O (TOS). An excellent photocatalytic activity of Fe/CNT-TiO2 was obtained for the degradation of methylene blue (MB) under visible light irradiation. It was considered that Fe cation could be doped into the matrix of TiO2, which could hinder the recombination rate of the excited electrons/holes. The photocatalytic activity of the composites was also found to depend on the presence of CNT. The synergistic effects among the Fe, CNT and TiO2 components were responsible for improving the visible light photocatalytic activity.
4,000원
4.
2010.05
구독 인증기관 무료, 개인회원 유료
The study was done to change the morphology and pore size of SBA-15 silica, and the characteristics of SBA-15 silica were investigated with TG-DSC, XRD, SEM, TEM and N2 adsorption-desorption under changing aging conditions. SBA-15 silica having a 2D-hexagonal structure was synthesized and confirmed by SEM and TEM. The structure of mesoporus silica SBA-15 showed a pore having regularly formed hexagonal structure and a passage having a cylindrical shape. This result is in good agreement with the pore forming in XRD and cylindrical shape of the structure in N2 adsorption-desorption isotherm. SBA-15 silica showed a large BET surface area of 603-698 m2/g, a pore volume of 0.673-0.926 cm3/g, a large pore diameter of 5.62-7.42 nm, and a thick pore wall of 3.31-4.37 nm. This result shows that as the aging temperature increases, the BET surface area, pore volume, and pore diameter increase but the pore wall thickness decreases. The BET surface areas in SM-2 and SM-3 are as large as 698 m2/g. However, SM-2 has a large surface area and forms a thick pore wall, when the aging temperature is 100˚C and is synthesized into stable mesoporous SBA-15 silica.
4,000원
5.
2010.05
구독 인증기관 무료, 개인회원 유료
A non-volatile resistive random access memory (RRAM) device with a Cr-doped SrZrO3/SrRuO3 bottom electrode heterostructure was fabricated on SrTiO3 substrates using pulsed laser deposition. During the deposition process, the substrate temperature was 650˚C and the variable ambient oxygen pressure had a range of 50-250 mTorr. The sensitive dependences of the film structure on the processing oxygen pressure are important in controlling the bistable resistive switching of the Cr-doped SrZrO3 film. Therefore, oxygen pressure plays a crucial role in determining electrical properties and film growth characteristics such as various microstructural defects and crystallization. Inside, the microstructure and crystallinity of the Cr-doped SrZrO3 film by oxygen pressure were strong effects on the set, reset switching voltage of the Cr-doped SrZrO3. The bistable switching is related to the defects and controls their number and structure. Therefore, the relation of defects generated and resistive switching behavior by oxygen pressure change will be discussed. We found that deposition conditions and ambient oxygen pressure highly affect the switching behavior. It is suggested that the interface between the top electrode and Cr-doped SrZrO3 perovskite plays an important role in the resistive switching behavior. From I-V characteristics, a typical ON state resistance of 100-200 Ω and a typical OFF state resistance of 1-2 kΩ, were observed. These transition metal-doped perovskite thin films can be used for memory device applications due to their high ON/OFF ratio, simple device structure, and non-volatility.
4,000원
6.
2010.05
구독 인증기관 무료, 개인회원 유료
ZnO nanostructures were grown on an Au seed layer by a hydrothermal method. The Au seed layer was deposited by ion sputter on a Si (100) substrate, and then the ZnO nanostructures were grown with different precursor concentrations ranging from 0.01 M to 0.3M at 150˚C and different growth temperatures ranging from 100˚C to 250˚C with 0.3 M of precursor concentration. FE-SEM (field-emission scanning electron microscopy), XRD (X-ray diffraction), and PL (photoluminescence) were carried out to investigate the structural and optical properties of the ZnO nanostructures. The different morphologies are shown with different growth conditions by FE-SEM images. The density of the ZnO nanostructures changed significantly as the growth conditions changed. The density increased as the precursor concentration increased. The ZnO nanostructures are barely grown at 100˚C and the ZnO nanostructure grown at 150˚C has the highest density. The XRD pattern shows the ZnO (100), ZnO (002), ZnO (101) peaks, which indicated the ZnO structure has a wurtzite structure. The higher intensity and lower FWHM (full width at half maximum) of the ZnO peaks were observed at a growth temperature of 150˚C, which indicated higher crystal quality. A near band edge emission (NBE) and a deep level emission (DLE) were observed at the PL spectra and the intensity of the DLE increased as the density of the ZnO nanostructures increased.
4,000원
7.
2010.05
구독 인증기관 무료, 개인회원 유료
Sn doped In2O3 (ITO) and ITO/Cu/ITO (ICI) multilayer films were prepared on glass substrates with a reactive radiofrequency (RF) magnetron sputter without intentional substrate heating, and then the influence of the Cu interlayer on themethanol gas sensitivity of the ICI films were considered. Although both ITO and ICI film sensors had the same thicknessof 100nm, the ICI sensors had a sandwich structure of ITO 50nm/Cu 5nm/ITO 45nm. The ICI films showed a ten timeshigher carrier density than that of the pure ITO films. However, the Cu interlayer may also have caused the decrement of carriermobility because the interfaces between the ITO and Cu interlayer acted as a barrier to carrier movement. Although the ICIfilms had two times a lower mobility than that of the pure ITO films, the ICI films had a higher conductivity of 3.6·10-4Ωcmdue to a higher carrier density. The changes in the sensitivity of the film sensors caused by methanol gas ranging from 50 to500ppm were measured at room temperature. The ICI sensors showed a higher gas sensitivity than that of the ITO single layersensors. Finally, it can be concluded that the ICI film sensors have the potential to be used as improved methanol gas sensors.
3,000원
8.
2010.05
구독 인증기관 무료, 개인회원 유료
In this paper two aspects of the percolation and conductivity of carbon black-filled polyethylene matrix composites will be discussed. Firstly, the percolation behavior, the critical exponent of conductivity of these composites, are discussed based on studying the whole change of resistivity, the relationship between frequency and relative permittivity or ac conductivity. There are two transitions of resistivity for carbon black filling. Below the first transition, resistivity shows an ohmic behavior and its value is almost the same as that of the matrix. Between the first and second transition, the change in resistivity is very sharp, and a non-ohmic electric field dependence of current has been observed. Secondly, the electrical conduction property of the carbon black-filled polyethylene matrix composites below the percolation threshold is discussed with the hopping conduction model. This study investigates the electrical conduction property of the composites below the percolation threshold based on the frequency dependence of conductivity in the range of 20 Hz to 1 MHz. There are two components for the observed ac loss current. One is independent of frequency that becomes prevalent in low frequencies just below the percolation threshold and under a high electrical field. The other is proportional to the frequency of the applied ac voltage in high frequencies and its origin is not clear. These results support the conclusion that the electrical conduction mechanism below the percolation threshold is tunneling.
4,000원
9.
2010.05
구독 인증기관 무료, 개인회원 유료
High Pressure High Temperature (HPHT) treatment can significantly change the color of diamonds. We studied the variation of the optical properties according to the nitrogen arrangement in natural brown diamonds of various types (type IaAB, type IaB, type IaA > B, type IaA< B, IaA = B) after HPHT treatment. The diamonds with different arrangements of nitrogen were annealed at temperatures in the range 1700-1800˚C under a stabilizing pressure of 5 GPa. HPHT treated samples were analyzed using UV-Vis-NIR, FT-IR, and PL spectroscopy. The absorption and luminescence spectra were measured to compare the variations of nitrogen arrangement in the natural brown diamonds before and after HPHT treatment. After HPHT treatment, the brown coloration in all types of diamonds was reduced and a decrease in the peaks related to the A-aggregate of nitrogen was more predominant than the B-aggregate. Furthermore, the peaks related to N3 (415.4 nm), H4 (496.4 nm), and platelet decreased and the peaks related to H3 (503.2 nm) and G-band increased after HPHT treatment. In conclusion, spectroscopic analysis of natural brown diamonds after HPHT treatment showed that a yellow color was produced by absorption in the H3 centers and a green color was generated by interaction between absorptions of the H3 and H2 centers.
4,200원
