The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
S Park - One of the best experts on this subject based on the ideXlab platform.
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Dust Particle Growth in rf silane plasmas using two-dimensional multi-pass laser light scattering
New Journal of Physics, 2009Co-Authors: Kil Byoung Chai, C.r. Seon, S Park, Wonho ChoeAbstract:We measured a spatio-temporal distribution of Particle size and a spatial Growth rate in a capacitively coupled silane plasma using in situ multi-pass laser light scattering. The two-dimensional measurement was accomplished using a low power He–Ne laser and a set of spherical mirrors across the plasma that enables us to span multiple beam paths over the plasma region in the vertical direction from the electrode sheath to the bulk plasma. In temporal, the measurement result shows two Particle Growth periods in which the fast Particle Growth (nucleation) is followed by the slow Particle Growth (coagulation). In spatial, the fastest Particle Growth occurred at the highest vertical position that corresponds to the furthest position from the sheath. The Particle coagulation modeling indicates that it is consistent with the largest proto Particle creation rate in the plasma bulk.
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Charge dependence of nano-Particle Growth in silane plasmas under UV irradiation
New Journal of Physics, 2009Co-Authors: C.r. Seon, Wonho Choe, K.b. Chai, H.y. Park, S ParkAbstract:The controlled generation of nano-Particles has been an important issue for the nano-structure formation in processing plasmas. We observed that the Particle Growth under UV irradiation was enhanced due to electric charge reduction of the Particles, suggesting that the variation of Particle charges could be a control parameter for the Particle Growth. The Particle Growth variation by UV irradiation is well described by the Particle coagulation model with time- dependent Particle charges in consideration, where predator Particles grow by adsorbing a few nanometer-sized proto-Particles.
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Effects of UV Irradiation on the Particle Growth in Low Pressure Silane Plasmas
2007 IEEE 34th International Conference on Plasma Science (ICOPS), 2007Co-Authors: C.r. Seon, Wonho Choe, K.b. Chai, H.y. Park, S Park, Yong-hyeon ShinAbstract:Summary form only given. The effects of UV irradiation on the Particle Growth were studied in low pressure capacitively-coupled silane plasmas. The growing speed of the Particles increased when UV was irradiated on the plasmas. The Particle Growth was monitored two dimensionally by the laser light scattering method. The Particles grew about 100 nm in diameter and dragged out toward the chamber wall by the ion drag force. The Growth and disappearance process of the Particles were faster in the discharge with the UV irradiation than that without the UV irradiation. The experiments were performed with various discharge conditions; the operating RF power range of 50 -100 W and the pressure range of 30 -100 m-Torr. For example, at 80 mTorr and 70 W, the Particles grew up to approximately 70 nm in time about 3 seconds faster with the UV irradiation than the case without the UV irradiation. This result is attributed to the Particle coagulation mechanism. The Particle Growth speed increases when the positive ion density increases in the silane plasmas. The photoemission from the initially-formed several nm size Particles is responsible for Particles having positive charges, which results in the increase of the Particle Growth speed. These results were also confirmed by the SEM photographs.
Alan Gallagher - One of the best experts on this subject based on the ideXlab platform.
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Particle Growth in silane-hydrogen discharges
Journal of Applied Physics, 2006Co-Authors: D. Kujundzic, Alan GallagherAbstract:The Growth of silicon Particles has been measured in silane-hydrogen radio-frequency (rf) discharges using a typical hydrogen/silane dilution ratio (20) and the pressure range (1.2–2.2Torr) used for the production of amorphous and microcrystalline silicon films and devices. By operating brief discharges without gas flow, the Particle size is obtained from the afterglow diffusion and the Particle density from the scattered-light intensity. These small-reactor data thus provide the expected Particle size and density versus location-in a commercial large-area–isothermal-flowing-gas reactor. Particle Growth rate is a strong function of pressure, whereas film Growth rate is almost independent of pressure. Both Growth rates are sensitive to rf voltage, although Particle Growth is more sensitive.
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The role of higher silanes in silane-discharge Particle Growth
Journal of Applied Physics, 2005Co-Authors: Gregory Bano, P. Horváth, Karoly Rozsa, Alan GallagherAbstract:A small concentration of stable higher silanes (HS) build up in an (initially) pure-silane discharge. Here it is shown that these HS cause a major increase in Particle Growth rates but have no effect on film Growth rates. This explains the observed increase of Growth rate during the first seconds of a transient discharge, as the HS build up toward a steady-state concentration of several percent. A rapid increase in Particle versus film Growth rate also occurs at larger values of discharge power and pressure, and the HS also appear to cause this. Possible reasons for this extreme sensitivity of Particles, but not of films, to the HS are evaluated.
C.r. Seon - One of the best experts on this subject based on the ideXlab platform.
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Dust Particle Growth in rf silane plasmas using two-dimensional multi-pass laser light scattering
New Journal of Physics, 2009Co-Authors: Kil Byoung Chai, C.r. Seon, S Park, Wonho ChoeAbstract:We measured a spatio-temporal distribution of Particle size and a spatial Growth rate in a capacitively coupled silane plasma using in situ multi-pass laser light scattering. The two-dimensional measurement was accomplished using a low power He–Ne laser and a set of spherical mirrors across the plasma that enables us to span multiple beam paths over the plasma region in the vertical direction from the electrode sheath to the bulk plasma. In temporal, the measurement result shows two Particle Growth periods in which the fast Particle Growth (nucleation) is followed by the slow Particle Growth (coagulation). In spatial, the fastest Particle Growth occurred at the highest vertical position that corresponds to the furthest position from the sheath. The Particle coagulation modeling indicates that it is consistent with the largest proto Particle creation rate in the plasma bulk.
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Charge dependence of nano-Particle Growth in silane plasmas under UV irradiation
New Journal of Physics, 2009Co-Authors: C.r. Seon, Wonho Choe, K.b. Chai, H.y. Park, S ParkAbstract:The controlled generation of nano-Particles has been an important issue for the nano-structure formation in processing plasmas. We observed that the Particle Growth under UV irradiation was enhanced due to electric charge reduction of the Particles, suggesting that the variation of Particle charges could be a control parameter for the Particle Growth. The Particle Growth variation by UV irradiation is well described by the Particle coagulation model with time- dependent Particle charges in consideration, where predator Particles grow by adsorbing a few nanometer-sized proto-Particles.
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Effects of UV Irradiation on the Particle Growth in Low Pressure Silane Plasmas
2007 IEEE 34th International Conference on Plasma Science (ICOPS), 2007Co-Authors: C.r. Seon, Wonho Choe, K.b. Chai, H.y. Park, S Park, Yong-hyeon ShinAbstract:Summary form only given. The effects of UV irradiation on the Particle Growth were studied in low pressure capacitively-coupled silane plasmas. The growing speed of the Particles increased when UV was irradiated on the plasmas. The Particle Growth was monitored two dimensionally by the laser light scattering method. The Particles grew about 100 nm in diameter and dragged out toward the chamber wall by the ion drag force. The Growth and disappearance process of the Particles were faster in the discharge with the UV irradiation than that without the UV irradiation. The experiments were performed with various discharge conditions; the operating RF power range of 50 -100 W and the pressure range of 30 -100 m-Torr. For example, at 80 mTorr and 70 W, the Particles grew up to approximately 70 nm in time about 3 seconds faster with the UV irradiation than the case without the UV irradiation. This result is attributed to the Particle coagulation mechanism. The Particle Growth speed increases when the positive ion density increases in the silane plasmas. The photoemission from the initially-formed several nm size Particles is responsible for Particles having positive charges, which results in the increase of the Particle Growth speed. These results were also confirmed by the SEM photographs.
Yongxiang Han - One of the best experts on this subject based on the ideXlab platform.
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Aerosol chemistry and Particle Growth events at an urban downwind site in North China Plain
Atmospheric Chemistry and Physics, 2018Co-Authors: Yingjie Zhang, Haofei Wang, Yuying Wang, Qingqing Wang, Haitao Zheng, Fang Zhang, Hongrong Shi, Yuxuan Bian, Yongxiang HanAbstract:Abstract. The North China Plain (NCP) has experienced frequent severe haze pollution events in recent years. While extensive measurements have been made in megacities, aerosol sources, processes, and Particle Growth at urban downwind sites remain less understood. Here, an aerosol chemical speciation monitor and a scanning mobility Particle sizer, along with a suite of collocated instruments, were deployed at the downwind site of Xingtai, a highly polluted city in the NCP, for real-time measurements of submicron aerosol (PM 1 ) species and Particle number size distributions during May and June 2016. The average mass concentration of PM 1 was 30.5 ( ±19.4 ) µ g m −3 , which is significantly lower than that during wintertime. Organic aerosols (OAs) constituted the major fraction of PM 1 (38 %), followed by sulfate (25 %) and nitrate (14 %). Positive matrix factorization with the multilinear engine version 2 showed that oxygenated OA (OOA) was the dominant species in OA throughout the study, on average accounting for 78 % of OA, while traffic and cooking emissions both accounted for 11 % of OA. Our results highlight that aerosol Particles at the urban downwind site were highly aged and mainly from secondary formation. However, the diurnal cycle also illustrated the substantial influence of urban emissions on downwind sites, which are characterized by similar pronounced early morning peaks for most aerosol species. New Particle formation and Growth events were also frequently observed (58 % of the time) on both clean and polluted days. Particle Growth rates varied from 1.2 to 4.9 nm h −1 and our results showed that sulfate and OOA played important roles in Particle Growth during clean periods, while OOA was more important than sulfate during polluted events. Further analyses showed that Particle Growth rates have no clear dependence on air mass trajectories.
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Aerosol chemistry and Particle Growth events at an urban downwind site in the North China Plain
2018Co-Authors: Yingjie Zhang, Haofei Wang, Yuying Wang, Qingqing Wang, Haitao Zheng, Fang Zhang, Hongrong Shi, Yuxuan Bian, Yongxiang HanAbstract:Abstract. The North China Plain (NCP) has experienced frequent severe haze pollution events in recent years. While extensive measurements have been made in megacities, aerosol sources, processes, and Particle Growth at urban downwind sites remain less understood. Here, an Aerosol Chemical Speciation Monitor and a Scanning Mobility Particle Sizer, along with a suite of collocated instruments, were deployed at the downwind site of Xingtai, a highly polluted city in the NCP, for real-time measurements of submicron aerosol (PM1) species and Particle number size distributions during May and June 2016. The average mass concentration of PM1 was 30.5 (±19.4) μg m−3, which is significantly lower than that during wintertime. Organic aerosols (OA) constituted the major fraction of PM1 (38 %) followed by sulfate (25 %) and nitrate (14 %). Positive matrix factorization with the Multilinear Engine version 2 showed that oxygenated OA (OOA) was the dominant species in OA throughout the study, on average accounting for 78 % of OA, while traffic and cooking emissions both accounted for 11 % of OA. Our results highlight that aerosol Particles at the urban downwind site were highly aged and mainly from secondary formation. However, the diurnal cycle also illustrated the substantial influence of urban emissions on downwind sites, which are characterized by similar pronounced early morning peaks for most aerosol species. New Particle formation and Growth events were also frequently observed (58 % of the time) on both clean and polluted days. Particle Growth rates varying from 1.2 to 4.9 nm h−1 were positively related to the condensation sink during periods with high OOA contributions and also to sulfate concentrations during relatively clean periods. Our results showed that sulfate and OOA played important roles in Particle Growth during clean periods, while OOA was more important than sulfate during polluted events. Further analyses showed that Particle Growth rates have no clear dependence on air mass trajectories.
Yingjie Zhang - One of the best experts on this subject based on the ideXlab platform.
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Characteristics of atmospheric fungi in Particle Growth events along with new Particle formation in the central North China Plain
The Science of the total environment, 2019Co-Authors: Nana Luo, Wenzhong Shi, Chen Liang, Haofei Wang, Wenji Zhao, Yingjie Zhang, Yuying Wang, Xing YanAbstract:The importance of fungi as cloud condensation nuclei (CCN) and ice-forming nuclei (IN) has been recognized for some researches. Particle Growth along with new Particle formation (NPF) play a joint role in modulating the CCN number concentration. Although fungi can accelerate the coalescence by large Particles, the specific contribution and characteristics of atmospheric fungi for Particle Growth, especially during NPF events, is poorly understood. In this study, aerosol size distribution data and air samples were collected at Xingtai, a suburban site in the central North China Plain, from 1 May to 1 June 2016. Using DNA sequence-based methods, atmospheric fungal communities were identified and quantified. Significant differences in fungal communities between Particle Growth events along with new Particle formation (PGE-NPF) and non-PGE-NPF events are found, especially for the Ascomycota and Basidiomycota phyla, and the Dothideomycetes, Saccharomycetes, and Tremellomycetes classes. At the genus level, five fungal communities were significantly different under PGE-NPF and non-PGE-NPF conditions, i.e., the Cladosporium, Capnodiales, Mrakia, Saccharomycetales and Trichocomaceae genera. The air mass source not only had an impact on NPF and the Particle Growth process, but also on the characteristics of the fungal communities. The fungal genus communities of Cladosporium, Capnodiales, Trichocomaceae, Mrakia, and Saccharomycetales may contribute to NPF and the Particle Growth process.
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Aerosol chemistry and Particle Growth events at an urban downwind site in North China Plain
Atmospheric Chemistry and Physics, 2018Co-Authors: Yingjie Zhang, Haofei Wang, Yuying Wang, Qingqing Wang, Haitao Zheng, Fang Zhang, Hongrong Shi, Yuxuan Bian, Yongxiang HanAbstract:Abstract. The North China Plain (NCP) has experienced frequent severe haze pollution events in recent years. While extensive measurements have been made in megacities, aerosol sources, processes, and Particle Growth at urban downwind sites remain less understood. Here, an aerosol chemical speciation monitor and a scanning mobility Particle sizer, along with a suite of collocated instruments, were deployed at the downwind site of Xingtai, a highly polluted city in the NCP, for real-time measurements of submicron aerosol (PM 1 ) species and Particle number size distributions during May and June 2016. The average mass concentration of PM 1 was 30.5 ( ±19.4 ) µ g m −3 , which is significantly lower than that during wintertime. Organic aerosols (OAs) constituted the major fraction of PM 1 (38 %), followed by sulfate (25 %) and nitrate (14 %). Positive matrix factorization with the multilinear engine version 2 showed that oxygenated OA (OOA) was the dominant species in OA throughout the study, on average accounting for 78 % of OA, while traffic and cooking emissions both accounted for 11 % of OA. Our results highlight that aerosol Particles at the urban downwind site were highly aged and mainly from secondary formation. However, the diurnal cycle also illustrated the substantial influence of urban emissions on downwind sites, which are characterized by similar pronounced early morning peaks for most aerosol species. New Particle formation and Growth events were also frequently observed (58 % of the time) on both clean and polluted days. Particle Growth rates varied from 1.2 to 4.9 nm h −1 and our results showed that sulfate and OOA played important roles in Particle Growth during clean periods, while OOA was more important than sulfate during polluted events. Further analyses showed that Particle Growth rates have no clear dependence on air mass trajectories.
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Aerosol chemistry and Particle Growth events at an urban downwind site in the North China Plain
2018Co-Authors: Yingjie Zhang, Haofei Wang, Yuying Wang, Qingqing Wang, Haitao Zheng, Fang Zhang, Hongrong Shi, Yuxuan Bian, Yongxiang HanAbstract:Abstract. The North China Plain (NCP) has experienced frequent severe haze pollution events in recent years. While extensive measurements have been made in megacities, aerosol sources, processes, and Particle Growth at urban downwind sites remain less understood. Here, an Aerosol Chemical Speciation Monitor and a Scanning Mobility Particle Sizer, along with a suite of collocated instruments, were deployed at the downwind site of Xingtai, a highly polluted city in the NCP, for real-time measurements of submicron aerosol (PM1) species and Particle number size distributions during May and June 2016. The average mass concentration of PM1 was 30.5 (±19.4) μg m−3, which is significantly lower than that during wintertime. Organic aerosols (OA) constituted the major fraction of PM1 (38 %) followed by sulfate (25 %) and nitrate (14 %). Positive matrix factorization with the Multilinear Engine version 2 showed that oxygenated OA (OOA) was the dominant species in OA throughout the study, on average accounting for 78 % of OA, while traffic and cooking emissions both accounted for 11 % of OA. Our results highlight that aerosol Particles at the urban downwind site were highly aged and mainly from secondary formation. However, the diurnal cycle also illustrated the substantial influence of urban emissions on downwind sites, which are characterized by similar pronounced early morning peaks for most aerosol species. New Particle formation and Growth events were also frequently observed (58 % of the time) on both clean and polluted days. Particle Growth rates varying from 1.2 to 4.9 nm h−1 were positively related to the condensation sink during periods with high OOA contributions and also to sulfate concentrations during relatively clean periods. Our results showed that sulfate and OOA played important roles in Particle Growth during clean periods, while OOA was more important than sulfate during polluted events. Further analyses showed that Particle Growth rates have no clear dependence on air mass trajectories.