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排序方式: 共有6343条查询结果,搜索用时 15 毫秒
981.
Lee JH Lee JW Hwang S Kim SY Cho HK Lee JY Park JS 《Journal of nanoscience and nanotechnology》2012,12(7):5598-5603
Al-doped ZnO (AZO) thin films with various Al concentrations were synthesized on Si(001) substrates with native oxide layers by atomic layer deposition process. The effects of the Al concentration on the microstructural characteristics of the AZO thin films grown at 250 degrees C and the correlation between their microstructural characteristics and electrical properties of the AZO thin films were investigated by AFM, XRD, HRTEM and Hall measurements. The XRD and HRTEM results revealed that the crystallinity and electrical properties of the undoped ZnO thin films were enhanced by 2.48 at% Al doping. However, 12.62 at% Al doping induced the deterioration of their crystallinity and electrical properties due to the formation of nano-sized metallic Al clusters and randomly oriented ZnO-based nano-crystals. To enhance the electrical properties of the AZO thin films while maintaining their crystallinity and electrical properties, a moderate Al concentration has to be chosen under the solubility limit of Al in ZnO. 相似文献
982.
Koh HJ Jang SH Kim CY Shin SC Kim YH Kwon SK 《Journal of nanoscience and nanotechnology》2012,12(5):4299-4304
New semiconductors having naphthalene and anthracene cores with hexylated bithiophene side units, 2,6-bis(5'-hexylbithiophen-2'-yl)naphthalene (HBT-NA) and 2,6-bis(5'-hexylbithiophen-2'-yl)anthracene (HBT-AN), were synthesized. HBT-AN and HBT-NA were characterized using FT-IR, 1H-NMR, Mass spectrum and elemental analysis. HBT-AN and HBT-NA showed well ordered crystalline with high thermal stabilities as evidenced by 5% weight loss at 447 degrees C for HBT-AN and 434 degrees C for HBT-NA. The closed packed structures between adjacent molecules were observed by studying UV-visible and photoluminescence (PL) in solution and film. The HOMO energy levels of HBT-NA and HBT-AN were found to be 5.47 eV and 5.42 eV, respectively. HBT-NA exhibits hole mobility of 8.4 x 10(-2) cm2Ns and on/off ratio of 5.6 x 10(5). HBT-AN shows 5.2 x 10(-2) cm2Ns and on/off ratio of 1.0 x 10(5). 相似文献
983.
Kim JY Rho JH Lee C Bae S Kim SJ Kim KS Hong BH Choi EJ 《Journal of nanoscience and nanotechnology》2012,12(7):5816-5819
It is known that low-field mobility of graphene depends largely on the substrate material on which it is transferred. We measured Drude optical conductivity of graphene on various substrates and determined the carrier density and carrier scattering rate. The carrier density varies widely depending on the substrate material. However the scattering rate is almost constant, approximately 100 cm(-1), for 5 different substrates. We calculate carrier mobility of graphene using the two quantities, i.e., carrier density and scattering rate, to find that it agrees with the mobility measured from dc transport experiment. We conclude that substrate-depent mobility of graphene originates from different carrier density but not from the scattering rate. 相似文献
984.
Park JH Jurng J Bae GN Park SH Jeon JK Kim SC Kim JM Park YK 《Journal of nanoscience and nanotechnology》2012,12(7):5942-5946
The catalytic oxidation of a representative volatile organic compound, benzene, with ozone at a low temperature was investigated. A nanoporous MCM-48 material with a high specific surface area was used as the support for the catalytic oxidation for the first time. Mn, which has high activity at a low temperature, was used as the metal catalyst. To examine the effect of the Mn precursor, MCM-48 was impregnated with two different Mn precursors: Mn acetate and Mn nitrate. The characteristics of the synthesized catalysts were analyzed by Brunauer Emmett Teller surface area, X-ray diffraction, X-ray photoelectron spectroscopy, and temperature-programmed reduction. MCM-48 impregnated with Mn acetate showed higher catalytic activity than MCM-48 impregnated with Mn nitrate. This result was attributed to the better dispersion within nanoporous MCM-48 and higher oxygen mobility of Mn oxides produced by Mn acetate. The catalytic activity was also shown to depend closely on the ozone concentration. 相似文献
985.
Kim KN Lee SK Lee HY Kim DH Lee JC Moon SJ 《Journal of nanoscience and nanotechnology》2012,12(5):4228-4232
A series of novel photoactive conjugated terpolymers based on N-alkyl carbazole, 9,9-didecylfluorene, and bis(thienyl)benzothiadiazole were synthesized by the Pd-catalyzed Suzuki polymerization method with various molar ratios of the carbazole derivatives. Electron-deficient benzothiadiazole and electron-rich carbazole moieties were incorporated into the polymer backbone to obtain the broad absorption spectrum and to improve the hole-transporting characteristics, respectively. The polymer solar cell (PSC) was fabricated with a layered structure of ITO/PEDOT: PSS/polymer:C71-PCBM (1:3)/LiF/Al. The best performance of PSC was obtained at P1:C71-PCBM whose reaches a power conversion efficiency (PCE) of 2.62%, with a short circuit current density (J(SC)) of 8.61 mA/cm2, an open circuit voltage (V(OC)) of 0.82 V, and a fill factor (FF) of 0.37 under AM 1.5 G irradiation (100 mW/cm2). 相似文献
986.
Gradient poly(2-hydroxyethyl methacrylate) brushes were synthesized by surface-initiated atom transfer radical polymerization (ATRP) confined within a microfluidic system on a silicon wafer. For ATRP, surface initiator, 11-((2-bromo, 2-methyl) propionyloxy) undecyltrichlorosilane (BUC), was synthesized, and allowed to self-assemble in a monolayer on the Si wafer, as analyzed by XPS to confirm the presence of an ester group of BUC. A solution containing 2-hydroxyethylmethacrylate, Cu catalyst, and bipyridin was allowed to flow in a microchannel and polymerize, resulting in the brushes with a gradient of thickness on the Si wafer. Using ellipsometry and ATR-IR, we verified the gradients of well established brushes on the Si wafer. AFM and contact angle data showed that wettability of the brushes did not exhibit a linear relationship with hydrophilicity. 相似文献
987.
Kim S Shin DO Choi DG Jeong JR Mun JH Yang YB Kim JU Kim SO Jeong JH 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(10):1563-1569
A highly efficient, ultralarge-area nanolithography that integrates block-copolymer lithography with single-step ZnO nanoimprinting is introduced. The UV-assisted imprinting of a photosensitive sol-gel precursor creates large-area ZnO topographic patterns with various pattern shapes in a single-step process. This straightforward approach provides a smooth line edge and high thermal stability of the imprinted ZnO pattern; these properties are greatly advantageous for further graphoepitaxial block-copolymer assembly. According to the ZnO pattern shape and depth, the orientation and lateral ordering of self-assembled cylindrical nanodomains in block-copolymer thin films could be directed in a variety of ways. Significantly, the subtle tunability of ZnO trench depth enabled by nanoimprinting, generated complex hierarchical nanopatterns, where surface-parallel and surface-perpendicular nanocylinder arrays are alternately arranged. The stability of this complex morphology is confirmed by self-consistent field theory (SCFT) calculations. The highly ordered graphoepitaxial nanoscale assembly achieved on transparent semiconducting ZnO substrates offers enormous potential for photonics and optoelectronics. 相似文献
988.
Nguyen XS Tay CB Fitzgerald EA Chua SJ 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(8):1204-8, 1125
The fabrication of a p-shell/n-core coaxial nanorod ZnO homojunction light-emitting diode by inexpensive solution method is demonstrated. The p-type conductivity of the ZnO shell arises from the incorporation of potassium while the n-type conductivity of the core is due to unintentional doping. 相似文献
989.
Jeong Hwan ChunKi Tae Park Dong Hyun JoJi Young Lee Sang Gon KimSun Hee Park Eun Sook LeeJy-Young Jyoung Sung Hyun Kim 《International Journal of Hydrogen Energy》2011,36(14):8422-8428
In this study, a gas diffusion layer (GDL) was modified to improve the water management ability of a proton exchange membrane fuel cell (PEMFC). We developed a novel hydrophobic/hydrophilic double micro porous layer (MPL) that was coated on a gas diffusion backing layer (GDBL). The water management properties, vapor and water permeability, of the GDL were measured and the performance of single cells was evaluated under two different humidification conditions, R.H. 100% and 50%. The modified GDL, which contained a hydrophilic MPL in the middle of the GDL and a hydrophobic MPL on the surface, performed better than the conventional GDL, which contained only a single hydrophobic MPL, regardless of humidity, where the performance of the single cell was significantly improved under the low humidification condition. The hydrophilic MPL, which was in the middle of the modified GDL, was shown to act as an internal humidifier due to its water absorption ability as assessed by measuring the vapor and water permeability of this layer. 相似文献
990.
Conventionally, there have been three basic ways of research on H2 production from H2O-splitting with solar energy: photo-catalytic, photo-electrochemical and thermochemical. Among them the thermal dissociation of H2O has been considered the most efficient, because it is a single step energy conversion process and gives much higher conversion efficiency than those resulted from other methods. However, the major stumbling block of thermal dissociation of H2O has been the requirement of a high dissociation temperature which causes problems both with materials for the reactor and with energy conversion efficiency for the process. In this study, we show that the dissociation temperature can be drastically lowered when H2O is thermally dissociated on solid acid materials. A probable mechanism of the thermal H2O-splitting on solid acid materials is also presented, based on some experimental results of this study and reports in the literature. 相似文献