The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Seongju Park - One of the best experts on this subject based on the ideXlab platform.
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enhanced optical power and low forward voltage of gan based light emitting diodes with ga doped zno transparent conducting layer
Applied Physics Letters, 2010Co-Authors: Taeyoung Park, Seongju Park, Yongseok Choi, Jangwon Kang, Jaeho Jeong, Dong Min JeonAbstract:Ga-doped ZnO (ZnO:Ga) films were grown by metalorganic chemical vapor deposition as transparent conducting layers for GaN light-emitting diodes (LEDs). The forward voltage of LEDs with ZnO:Ga was 3.3 V at 20 mA. The low forward voltage was attributed to the removal of a resistive ZnGa2O4 phase, decreased resistivity of ZnO:Ga films, and increased Hole Concentration in p-GaN by thermal annealing process. The light output power of LEDs with ZnO:Ga was increased by 25% at 20 mA compared to that of LEDs with Sn-doped indium oxide due to the enhanced transmittance and the increased Hole Concentration in p-GaN.
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low resistance nonalloyed ni au ohmic contacts to p gan irradiated by krf excimer laser
Applied Physics Letters, 2006Co-Authors: Minsuk Oh, Daekue Hwang, Changgoo Kang, Seongju ParkAbstract:A specific contact resistance of 8.9×10−5Ωcm2 was obtained for a Ni∕Au Ohmic layer on the KrF laser-irradiated p-GaN. It was found that laser irradiation increases the Hole Concentration from 4.1×1017to9.7×1017cm−3 by removing hydrogen atoms from p-GaN layer. The native oxide was also removed as evidenced by the Ga 2p peak shift and the decrease in the intensity of O 1s peak in the x-ray photoelectron spectra. The formation of a low resistance is attributed to the increase in the Hole Concentration and the removal of native oxide from p-GaN by laser irradiation.
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formation and effect of thermal annealing for low resistance ni au ohmic contact to phosphorous doped p type zno
Journal of The Electrochemical Society, 2005Co-Authors: Jaehong Lim, Kyoungkook Kim, Daekue Hwang, Hyunsik Kim, Seongju ParkAbstract:We report on a Ni (30 nm)/Au (80 nm) metallization scheme for low-resistance ohmic contacts to the phosphorus-doped p-type ZnO with a Hole Concentration of cm−3. As-deposited Ni/Au contacts to p-type ZnO showed a specific contact resistance of Ω cm2 by forming Ni-Zn phase to increase the Hole Concentration near the ZnO surface. The specific contact resistance was decreased with increasing the thermal annealing temperature. When the Ni/Au contact was annealed at 600°C for 30 s in an air ambient, the specific contact resistance was greatly decreased to Ω cm2. The improved ohmic property was attributed to an increase in the Hole Concentration by the formation of Ni-Zn and Au-Zn phases due to the outdiffusion of Zn during the thermal annealing process. © 2005 The Electrochemical Society. All rights reserved.
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formation and effect of thermal annealing for low resistance ni au ohmic contact to phosphorous doped p type zno
Journal of The Electrochemical Society, 2005Co-Authors: Daekue Hwang, Jinyong Oh, Seongju ParkAbstract:We report on a Ni (30 nm)/Au (80 nm) metallization scheme for low-resistance ohmic contacts to the phosphorus-doped p-type ZnO with a Hole Concentration of 1.0 × 10 1 8 cm - 3 . As-deposited Ni/Au contacts to p-type ZnO showed a specific contact resistance of 7.67 X 10 - 3 Ω cm 2 by forming Ni-Zn phase to increase the Hole Concentration near the ZnO surface. The specific contact resistance was decreased with increasing the thermal annealing temperature. When the Ni/Au contact was annealed at 600°C for 30 s in an air ambient, the specific contact resistance was greatly decreased to 1.72 X 10 - 4 Ω cm 2 . The improved ohmic property was attributed to an increase in the Hole Concentration by the formation of Ni-Zn and Au-Zn phases due to the outdiffusion of Zn during the thermal annealing process.
Makoto Kasu - One of the best experts on this subject based on the ideXlab platform.
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maximum Hole Concentration for hydrogen terminated diamond surfaces with various surface orientations obtained by exposure to highly concentrated no2
Diamond and Related Materials, 2013Co-Authors: Hisashi Sato, Makoto KasuAbstract:Abstract NO2 exposure drastically increases the Hole Concentration on the surface of hydrogen (H)-terminated diamond. When the NO2 gas Concentration is higher than 300 ppm, the saturated Hole sheet Concentration ps stays the same. Therefore, the ps value is regarded as the high limit of the Concentration of Holes on H-terminated diamond surface, ps,max. In this work, we compared ps,max, mobility μ, and sheet resistance Rs for (100), (110), and (111) H-terminated surfaces of chemical-vapor-deposited single-crystal diamond. On (110), (111), (100) surfaces, the ps,max values are 1.717 × 1014 and 1.512 × 1014 cm− 2, and 0.981 × 1014, respectively. This result supports the first-principle calculations: the Hole Concentration depends on the energy difference between the valence band maximum and the unoccupied orbitals of adsorbent NO2 molecules. We have achieved Rs of 719.3 Ω/sq (ps = 1.456 × 1014 cm− 2 and μ = 59.6 cm2 V− 1 s− 1), the lowest reported so far, on (111) surfaces under 20,000-ppm NO2 atmosphere.
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enhancement and stabilization of Hole Concentration of hydrogen terminated diamond surface using ozone adsorbates
Japanese Journal of Applied Physics, 2010Co-Authors: Michal Kubovic, Makoto KasuAbstract:The p-type conductivity of H-terminated diamond surface can be linked to adsorption of a specific gas species on the surface. O3, NO2, NO, and SO2 were identified as adsorbates, which induce Holes on the H-terminated diamond surface. Among them, exposure to O3 increases Hole Concentration the most. The O3-increased Concentration remains high even after exposure to the gas has stopped, indicating that ozone is the most stable adsorbent. X-ray photospectroscopy spectra of O3-adsorbed H-terminated diamond surface show partial oxidation of the surface and upward band bending and are very similar to those of NO2 exposed diamond surfaces.
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sorption properties of no2 gas and its strong influence on Hole Concentration of h terminated diamond surfaces
Applied Physics Letters, 2010Co-Authors: Michal Kubovic, Makoto Kasu, Hiroyuki KageshimaAbstract:The Hole Concentration of hydrogen-terminated diamond surfaces was studied during exposure to different Concentrations of NO2 gas. The Hole Concentration increased during adsorption of NO2 molecules on the diamond surface, and decreased when the exposure stopped and NO2 molecules desorbed from the surface. The increase in Hole Concentration can be directly linked to the NO2 Concentration. The low NO2 Concentration in air (∼20 ppb) is responsible the Hole Concentration normally measured in air, and with increasing NO2 Concentration the maximum Hole Concentration increases even more. The time evolution of Hole Concentration was analyzed using the Elovich sorption model. Further analysis based on the Ritchie model indicated that an adsorbed NO2 molecule occupies two different surface sites. Temperature-dependent measurements indicate low activation energy between 0.1 and 0.2 eV.
Daekue Hwang - One of the best experts on this subject based on the ideXlab platform.
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low resistance nonalloyed ni au ohmic contacts to p gan irradiated by krf excimer laser
Applied Physics Letters, 2006Co-Authors: Minsuk Oh, Daekue Hwang, Changgoo Kang, Seongju ParkAbstract:A specific contact resistance of 8.9×10−5Ωcm2 was obtained for a Ni∕Au Ohmic layer on the KrF laser-irradiated p-GaN. It was found that laser irradiation increases the Hole Concentration from 4.1×1017to9.7×1017cm−3 by removing hydrogen atoms from p-GaN layer. The native oxide was also removed as evidenced by the Ga 2p peak shift and the decrease in the intensity of O 1s peak in the x-ray photoelectron spectra. The formation of a low resistance is attributed to the increase in the Hole Concentration and the removal of native oxide from p-GaN by laser irradiation.
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formation and effect of thermal annealing for low resistance ni au ohmic contact to phosphorous doped p type zno
Journal of The Electrochemical Society, 2005Co-Authors: Jaehong Lim, Kyoungkook Kim, Daekue Hwang, Hyunsik Kim, Seongju ParkAbstract:We report on a Ni (30 nm)/Au (80 nm) metallization scheme for low-resistance ohmic contacts to the phosphorus-doped p-type ZnO with a Hole Concentration of cm−3. As-deposited Ni/Au contacts to p-type ZnO showed a specific contact resistance of Ω cm2 by forming Ni-Zn phase to increase the Hole Concentration near the ZnO surface. The specific contact resistance was decreased with increasing the thermal annealing temperature. When the Ni/Au contact was annealed at 600°C for 30 s in an air ambient, the specific contact resistance was greatly decreased to Ω cm2. The improved ohmic property was attributed to an increase in the Hole Concentration by the formation of Ni-Zn and Au-Zn phases due to the outdiffusion of Zn during the thermal annealing process. © 2005 The Electrochemical Society. All rights reserved.
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formation and effect of thermal annealing for low resistance ni au ohmic contact to phosphorous doped p type zno
Journal of The Electrochemical Society, 2005Co-Authors: Daekue Hwang, Jinyong Oh, Seongju ParkAbstract:We report on a Ni (30 nm)/Au (80 nm) metallization scheme for low-resistance ohmic contacts to the phosphorus-doped p-type ZnO with a Hole Concentration of 1.0 × 10 1 8 cm - 3 . As-deposited Ni/Au contacts to p-type ZnO showed a specific contact resistance of 7.67 X 10 - 3 Ω cm 2 by forming Ni-Zn phase to increase the Hole Concentration near the ZnO surface. The specific contact resistance was decreased with increasing the thermal annealing temperature. When the Ni/Au contact was annealed at 600°C for 30 s in an air ambient, the specific contact resistance was greatly decreased to 1.72 X 10 - 4 Ω cm 2 . The improved ohmic property was attributed to an increase in the Hole Concentration by the formation of Ni-Zn and Au-Zn phases due to the outdiffusion of Zn during the thermal annealing process.
M Tanimoto - One of the best experts on this subject based on the ideXlab platform.
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universal intrinsic scale of the Hole Concentration in high t c cuprates
Physical Review B, 2004Co-Authors: T Honma, P H Hor, H H Hsieh, M TanimotoAbstract:We have measured thermoelectric power (TEP) as a function of Hole Concentration per ${\mathrm{CuO}}_{2}$ layer ${P}_{pl}$ in ${\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6}$ $({P}_{pl}=x∕2)$ with no oxygen in the $\mathrm{Cu}\text{\ensuremath{-}}\mathrm{O}$ chain layer. The room-temperature TEP as a function of ${P}_{pl}$, ${S}^{290}({P}_{pl})$, of ${\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6}$ behaves identically to that of ${\mathrm{La}}_{2\ensuremath{-}z}{\mathrm{Sr}}_{z}{\mathrm{CuO}}_{4}$ $({P}_{pl}=z)$. We argue that ${S}^{290}({P}_{pl})$ represents a measure of the intrinsic equilibrium electronic states of doped Holes and, therefore, can be used as a common scale for the carrier Concentrations of layered cuprates. We shows that the ${P}_{pl}$ determined by this new universal scale is consistent with both Hole Concentration microscopically determined by NQR and the Hole Concentration macroscopically determined by the formal valency of $\mathrm{Cu}$. We find two characteristic scaling temperatures, ${T}_{S}^{*}$ and ${T}_{S2}^{*}$, in the TEP versus temperature curves that change systematically with doping. Based on the universal scale, we uncover a universal phase diagram in which almost all the experimentally determined pseudogap temperatures as a function of ${P}_{pl}$ fall on two common curves; lower pseudogap temperature defined by the ${T}_{S}^{*}$ versus ${P}_{pl}$ curve and upper pseudogap temperature defined by the ${T}_{S2}^{*}$ versus ${P}_{pl}$ curve. We find that while pseudogaps are intrinsic properties of doped Holes of a single ${\mathrm{CuO}}_{2}$ layer for all high-${T}_{c}$ cuprates, ${T}_{c}$ depends on the number of layers, therefore, the inter layer coupling, in each individual system.
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a universal intrinsic scale of Hole Concentration for high tc cuprates
arXiv: Superconductivity, 2003Co-Authors: T Honma, P H Hor, H H Hsieh, M TanimotoAbstract:We have measured thermoelectric power (TEP) as a function of Hole Concentration per CuO2 layer, Ppl, in Y1-xCaxBa2Cu3O6 (Ppl = x/2) with no oxygen in the Cu-O chain layer. The room-temperature TEP as a function of Ppl, S290(Ppl), of Y1-xCaxBa2Cu3O6 behaves identically to that of La2-zSrzCuO4 (Ppl = z). We argue that S290(Ppl) represents a measure of the intrinsic equilibrium electronic states of doped Holes and, therefore, can be used as a common scale for the carrier Concentrations of layered cuprates. We shows that the Ppl determined by this new universal scale is consistent with both Hole Concentration microscopically determined by NQR and the Hole Concentration macroscopically determined by the Cu valency. We find two characteristic scaling temperatures, TS* and TS2*, in the TEP vs. temperature curves that change systematically with doping. Based on the universal scale, we uncover a universal phase diagram in which almost all the experimentally determined pseudogap temperatures as a function of Ppl fall on two common curves; upper pseudogap temperature defined by the TS* versus Ppl curve and lower pseudogap temperature defined by the TS2* versus Ppl curve. We find that while pseudogaps are intrinsic properties of doped Holes of a single CuO2 layer for all high-Tc cuprates, Tc depends on the number of layers, therefore the inter-layer coupling, in each individual system.
Uichiro Mizutani - One of the best experts on this subject based on the ideXlab platform.
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Hole Concentration dependence of electrical resistivity in the bi pb 2 sr la 2cuo6 δ quantitative evaluation with angle resolved photoemission spectroscopy
Journal of Electron Spectroscopy and Related Phenomena, 2005Co-Authors: Takeshi Kondo, T Takeuchi, T Yokoya, S Tsuda, S Shin, Uichiro MizutaniAbstract:Abstract Relaxation time of Bloch states at the Fermi level ( τ F ), Fermi velocity ( v F ), and mean free path ( l F ) of the conduction electrons in the (Bi, Pb)2(Sr, La)2CuO6+δ (Bi2201) superconductors with various Hole-Concentration (p) were determined by the angle-resolved photoemission spectroscopy (ARPES) measurement with high energy- and momentum-resolutions; Δ E = 10 meV and Δ k = 0.005 A−1. We found that τ F at k F along ( 0 , 0 ) – ( π , π ) cut is kept constant over a wide Hole-Concentration range while it in the vicinity of ( π , 0 ) is drastically shortened with decreasing p and eventually reaches nearly zero in the under-doped sample with the transition temperature of 27 K. By calculating electrical resistivity and comparing it with the measured one, we confirmed that τ F , v F , and l F determined by the ARPES measurement can be used for the quantitative estimation of the electrical transport properties, such as the electrical resistivity, in high- T c cuprates.
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Hole Concentration dependence of band structure in bi pb 2 sr la 2cuo6 δ determined by the angle resolved photoemission spectroscopy
Journal of Electron Spectroscopy and Related Phenomena, 2004Co-Authors: Takeshi Kondo, T Takeuchi, T Yokoya, S Tsuda, S Shin, Uichiro MizutaniAbstract:Abstract Energy–momentum ( E – k ) dispersion and the shape of the Fermi surface (FS) in the (Bi,Pb) 2 (Sr,La) 2 CuO 6+ δ (Bi2201) superconductors of various Hole-Concentrations were investigated by the angle-resolved photoemission spectroscopy (ARPES) with high energy and momentum resolutions (Δ E =10 meV and Δ k =0.005 A −1 ). The E – k dispersion is kept rigid and the chemical potential moves towards lower or higher energies with increasing or decreasing Hole-Concentration, respectively, over a wide Hole-Concentration range from the nearly optimal-doped condition with a transition temperature of 32 K to a heavily over-doped condition where the superconducting transition disappears. By comparing the shape of the FS determined for the present Bi2201 with that reported for the Bi 2 Sr 2 CaCu 2 O 8+ δ (Bi2212), we found that the area surrounded by the FS in the Bi2201 is fairly larger than that in the Bi2212. Estimated Hole-Concentration in the Bi2201 was found to vary from 0.25 to 0.43 Holes/Cu, that is more than twice as large as that in the optimally doped La 2− x Sr x CuO 4 (LSCO) and Bi2212 superconductors of 0.17 Holes/Cu.
