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85 results on '"Yoo, J. B."'

5. Enhanced field emission properties of thin-multiwalled carbon nanotubes: Role of SiOx coating.

Author

Moon, J. S., Alegaonkar, P. S., Han, J. H., Lee, T. Y., Yoo, J. B., and Kim, J. M.

Subjects
FIELD emission, SILICON oxide, CARBON, NANOSTRUCTURED materials, TRANSMISSION electron microscopy, GRAVIMETRIC analysis, FOURIER transform infrared spectroscopy
Abstract

We report the fabrication, characterization, and field emission properties of (silicon oxide) SiOx coated thin-multiwalled carbon nanotubes (t-MWNTs). The coated t-MWNTs show improved field emission behavior. Initially, raw t-MWNTs (diameter ∼5–8 nm) were functionalized by acid treatment. Using spin on glass as a Si precursor, SiOx was coated on the nanotubes by routine chemical methods. The coated samples were characterized by high resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA) techniques. The HRTEM results show that the local thickness of the coating varies from ∼1 to 2 nm. The FTIR investigations show the formation of nanophases, such as Si–C, Si–O–C, and intercalated Si–O, at the coating/nanotube interface. The TGA reveals that the coating prevents the high-temperature oxidation and degradation of the nanotubes. The field emission characteristics of the coated, functionalized, and raw nanotubes show that the turn-on fields and current density are improved for the coated nanotubes. This improvement was attributed to the lowering of the work function and dielectric constant of the C/SiOx interface layer and the localization of the density of states close to the Fermi energy for the coated nanotubes. The analysis of the emission stability spectra shows that the coated nanotubes have a more favorable lifetime. The observed enhancement was attributed to the protection of the nanotubes from the reactive sputter etching during the field emission process. The details of the analysis are presented. [ABSTRACT FROM AUTHOR]

Published
2006
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7. Dynamic phase-error compensation for high-resolution InP arrayed-waveguide grating using electro-optic effect

Author

Jiang, W., Fontaine, K., Soares, F. M., Baek, J. H., Okamoto, K., Yoo, J. B., Olsson, Fredrik, Lourdudoss, Sebastian, Jiang, W., Fontaine, K., Soares, F. M., Baek, J. H., Okamoto, K., Yoo, J. B., Olsson, Fredrik, and Lourdudoss, Sebastian

Abstract

We demonstrate for the first time the phase-error compensation for a 20-GHz-spacing InP AWG with electrooptic phase shifters placed on 42 arrayed waveguides. The experiment results show successful phase control and 6-dB reduction of crosstalk., QC 20141015

Published
2008
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8. Structural Changes of MoS 2 Nano-powder in Dependence on the Annealing Temperature

Author

Berdinsky, A.S., Chadderton, Lewis, Yoo, J B, Gutakovsky, A.K., Fedorov, V.E., Mazalov, L N, Fink, Dietmar, Berdinsky, A.S., Chadderton, Lewis, Yoo, J B, Gutakovsky, A.K., Fedorov, V.E., Mazalov, L N, and Fink, Dietmar

Abstract

To search for structural changes of molybdenum disulphide (MoS2) nano-powder under thermal treatment, the annealing of the powder was carried out in vacuum or in argon. MoS2 powder with a grain size of 3-5 nm was synthesized by a chemical method. The temperature of annealing was varied in the range of 380-1000 °C. The time of annealing was varied in the range from 4 h (380 °C) to 5 min (1000 °C). X-ray diffraction and transmission electron microscopy analyses were made to see the character of the change of the crystallization process and the curvature of (002) MoS2 planes. The increase of crystalline phase and the decrease of amorphous phase in the powder appears as a result of the rise of the annealing temperature. The sample annealed at Tann = 380 °C and 500 °C has a small curvature of (002) planes and more enlarged grains in comparison with non-annealed MoS 2 powder. The increase of the annealing temperature to T ann = 700 °C leads to a strong curvature of the (002) planes. The character of the curved planes varies from quite long planes with a large radius of curvature to right-angle-form and U-form structures. The increase of the annealing temperature to Tann = 1000 °C leads to a strong crystallization of the powder and a reduction of the amorphous phase.

Published
2005

9. Conducting Properties of Planar Irradiated and Pristine Silicon-fullerite-metal Structures

Author

Berdinsky, A.S., Fink, Dietmar, Yoo, J B, Chun, H.G., Chadderton, Lewis, Petrov, A V, Berdinsky, A.S., Fink, Dietmar, Yoo, J B, Chun, H.G., Chadderton, Lewis, and Petrov, A V

Abstract

Au/C60/p-Si sandwich structures can be easily obtained by evaporation of a thin fullerite (C60) film on a silicon substrate and a thin Au film on top of the C60 film. In this case a C 60/p-Si p-n heterojunction appears. Both the dark and photoconductivities of the planar pristine and irradiated Au/C60/p-Si structures were measured as a function of the irradiation fluence. Furthermore, the pressure dependence of these structures was determined. A strong dependence on the irradiation damage was found.

Published
2005

11. Electronic Conduction Properties of Au/C 60 /p-Si and C 60 /Au/p-Si Sandwich Structures: I-V and Transducer Characteristics

Author

Berdinsky, A.S., Fink, Dietmar, Yoo, J B, Chadderton, Lewis, Chun, H.G., Han, J H, Dragunov, V.P., Berdinsky, A.S., Fink, Dietmar, Yoo, J B, Chadderton, Lewis, Chun, H.G., Han, J H, and Dragunov, V.P.

Abstract

Gold-fullerite [C 60]-silicon (p-type) sandwich structures have been fabricated in order to investigate intrinsic cross-sectional and planar electronic conductive properties, in particular the C 60/p-Si p-n heterojunction. The turn-on voltage of this p-n

Published
2004

12. Study on growth of hollow nanoparticles of alumina

Author

Kulkarni, Naveen V., primary, Karmakar, Soumen, additional, Asthana, Srinanadan N., additional, Nawale, Ashok B., additional, Sheikh, Arif, additional, Patole, Shashikant P., additional, Yoo, J. B., additional, Mathe, Vikas L., additional, Das, Ashok K., additional, and Bhoraskar, Sudha V., additional

Published
2010
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23. Electron emission from carbon nanotube-dispersed MgO layer

Author

Heo, J. N., primary, Lee, J. H., additional, Jeong, T. W., additional, Lee, C. S., additional, Kim, W. S., additional, Jin, Y. W., additional, Kim, J. M., additional, Yu, SeGi, additional, Yi, W. K., additional, Park, S. H., additional, Oh, T. S., additional, and Yoo, J. B., additional

Published
2005
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26. Development of triode-type carbon nanotube field-emitter arrays with suppression of diode emission by forming electroplated Ni wall structure

Author

Jung, J. E., primary, Choi, J. H., additional, Park, Y. J., additional, Lee, H. W., additional, Jin, Y. W., additional, Chung, D. S., additional, Park, S. H., additional, Jang, J. E., additional, Hwang, S. Y., additional, Ko, T. Y., additional, Choi, Y. S., additional, Cho, S. H., additional, Lee, C. G., additional, You, J. H., additional, Lee, N. S., additional, Yoo, J. B., additional, and Kim, J. M., additional

Published
2003
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33. Conducting properties of planar irradiated and pristine silicon-fullerite-metal structures.

Author

Berdinsky, A. S., Fink, D., Yoo, J. B., Chun, H. G., Chadderton, L. T., and Petrov, A. V.

Subjects
THIN films, SILICON, PHOTOCONDUCTIVITY, IRRADIATION, HETEROJUNCTIONS
Abstract

Au/C60/p-Si sandwich structures can be easily obtained by evaporation of a thin fullerite (C60) film on a silicon substrate and a thin Au film on top of the C60 film. In this case a C60/p-Si p-n heterojunction appears. Both the dark and photoconductivities of the planar pristine and irradiated Au/C60/p-Si structures were measured as a function of the irradiation fluence. Furthermore, the pressure dependence of these structures was determined. A strong dependence on the irradiation damage was found. [ABSTRACT FROM AUTHOR]

Published
2005
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34. Increased peripheral androgen activity in infertile Korean women with polycystic ovaries.

Author

Roh, J. S., Yoo, J. B., and Hwang, Y. Y.

Abstract

The present investigation was designed to determine whether infertile women with polycystic ovaries (PCO) have sonographic or endocrinological differences compared with women with PCO proven to be fertile. Sonographic morphology of the ovary was not significantly different between the groups. However, serum concentrations of 3alpha-androstanediol glucuronide (3alpha-diolG) were significantly higher in infertile women with PCO than in those proven to be fertile. Furthermore, a significant positive correlation was noted between 3alpha-diolG and luteinizing hormone (LH) in infertile women, but not in those who were fertile. The higher correlation between serum 3alpha-diolG concentrations and serum LH concentrations seen in infertile women with PCO, with the lack of a significant difference in LH concentrations between infertile and fertile women, suggests that serum 3alpha-diolG may be a leading cause of subfertility in women with PCO. Accordingly, our evidence for increased 3alpha-diolG in the infertile group needs to be confirmed by further studies, including direct 5alpha-reductase assay, adrenal function tests and evaluation of hepatic conjugation activity. [ABSTRACT FROM AUTHOR]

Published
1999
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46. High-performance InGaAs/InP avalanche photodiode for a 2.5 Gb s-1 optical receiver

Author

Park, C. Y., Hyun, K. S., Kang, S. K., Song, M. K., Yoon, T. Y., Kim, H. M., Park, H. M., Park, S. -C., Lee, Y. H., Lee, C., and Yoo, J. B

Abstract

High-speed mesa type SAGCM avalanche photodiodes for 2.5 Gb s-1 optical receivers have been realized for the first time. The device is designed by dimensional analysis based on the electric field distribution in a multiplication layer and a charge plate layer. Very low dark current and high gain are obtained with an active region of 30 µm diameter. From the 1.55 µm wavelength 2.488 Gb s-1 transmission experiment, sensitivity of-33.6 dBm is measured using pseudorandom (223–1) NRZ patterns.

Published
1995
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49. Field emission study of Te nanowire arrays grown on conducting silicon substrate.

Author

Yan, Changzeng, Raghavan, C. M., Patole, Shashikant. P., Yoo, J. B., and Kang, Dae Joon

Abstract

In this communication, synthesis of high quality and length controlled Te nanowire arrays directly grown on silicon substrate with and without the coating of seed layer by a facile hydrothermal method was reported. The most preferential orientation of tellurium NW's was found along [001] through micro structural investigation. Field emission properties of as grown and annealed under Ar: H2 reduction atmosphere are studied meticulously. The emission current density of vacuum annealed Te nanowire arrays was found to be 25μA/cm2 at 3.0 V/μm. [ABSTRACT FROM PUBLISHER]

Published
2012
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