The material loss caused by bubble collapse during the micro-nano bubbles auxiliary chemical mechanical polishing(CMP)process cannot be ignored.In this study,the material removal mechanism of cavitation in the polishi...The material loss caused by bubble collapse during the micro-nano bubbles auxiliary chemical mechanical polishing(CMP)process cannot be ignored.In this study,the material removal mechanism of cavitation in the polishing process was investigated in detail.Based on the mixed lubrication or thin film lubrication,bubble-wafer plastic deformation,spherical indentation theory,Johnson-Cook(J-C)constitutive model,and the assumption of periodic distribution of pad asperities,a new model suitable for micro-nano bubble auxiliary material removal in CMP was developed.The model integrates many parameters,including the reactant concentration,wafer hardness,polishing pad roughness,strain hardening,strain rate,micro-jet radius,and bubble radius.The model reflects the influence of active bubbles on material removal.A new and simple chemical reaction method was used to form a controllable number of micro-nano bubbles during the polishing process to assist in polishing silicon oxide wafers.The experimental results show that micro-nano bubbles can greatly increase the material removal rate(MRR)by about 400%and result in a lower surface roughness of 0.17 nm.The experimental results are consistent with the established model.In the process of verifying the model,a better understanding of the material removal mechanism involved in micro-nano bubbles in CMP was obtained.展开更多
A continuous flow streamwise thermal gradientcloud condensation nuclei(CCN)counter with anaerosol focusing and a laser-charge-coupled device(CCD)camera detector system was developed here.The countingperformance of the...A continuous flow streamwise thermal gradientcloud condensation nuclei(CCN)counter with anaerosol focusing and a laser-charge-coupled device(CCD)camera detector system was developed here.The countingperformance of the laser-CCD camera detector system wasevaluated by comparing its measured number concentrationswith those measured with a condensation particlecounter(CPC)using polystyrene latex(PSL)and NaClparticles of varying sizes.The CCD camera parameters(e.g.brightness,gain,gamma,and exposure time)wereoptimized to detect moving particles in the sensing volumeand to provide the best image to count them.The CCNcounter worked well in the particle number concentrationrange of 0.6-8000#·cm^(-3)and the minimum detectablesize was found to be 0.5μm.The supersaturation in theCCN counter with varying temperature difference wasdetermined by using size-selected sodium chloride particlesbased on Köhler equation.The developed CCNcounter was applied to investigate CCN activity ofatmospheric ultrafine particles at 0.5%supersaturation.Data showed that CCN activity increased with increasingparticle size and that the higher CCN activation forultrafine particles occurred in the afternoon,suggesting thesignificant existence of hygroscopic or soluble species inphotochemically-produced ultrafine particles.展开更多
Three types of water-based condensational growth systems, which can enable particles to grow in size to facilitate sampling and subsequent chemical analysis, were evaluated. The first one is a mixing type growth syste...Three types of water-based condensational growth systems, which can enable particles to grow in size to facilitate sampling and subsequent chemical analysis, were evaluated. The first one is a mixing type growth system where aerosols are mixed with saturated water vapor, the second one is a thermal diffusive growth system where warm flow enters cold-walled tube, and the third one is a laminar flow type where cold flow enters a warm wet-wall tube. Hygroscopic sodium chloride (NaCl), ammonium sulfate ((NH4)2SO4) and ammonium nitrate (NH4N03), and non-hygroscopic polystyrene latex (PSL) particles, in the size range of 50-400 nm, were used to determine their growth factors through the growth systems. Our data showed that the third-type growth system could enable particles to grow most efficiently regardless of their hygroscopic property. Collection efficiency of particles in the size range of 0.05-2.5 μm, in a continuous aerosol sampler after they passed through the third-type growth system was about 100%, suggesting that the third-type growth system would he the most useful among the tested growth systems for sampling and subsequent chemical analysis of fine and ultrafine particles.展开更多
Size distributions of ambient aerosols at the Fresno Supersite were measured with four commercially available scanning mobility particle sizers (SMPS). TSI nano, TSI standard, Grimm, and MSP instruments were colloca...Size distributions of ambient aerosols at the Fresno Supersite were measured with four commercially available scanning mobility particle sizers (SMPS). TSI nano, TSI standard, Grimm, and MSP instruments were collocated at the Fresno Supersite and particle size distributions were measured continuously from August 18 through September 18, 2005. For particles with diameters between 10 and 200 nm, differences among hourly-average ambient particle concentrations ranged from 0% between the TSI nano and Grimm in the 30-50 nm size range to 39% between the Grimm and MSP in the 10-30 nm size range. MSP concentrations were 10-33% lower than those measured with the TSI standard for particles smaller than 200 nm. The TSI nano and TSI standard agreed to within 5% in their overlapping size range (10-84 nm). The TSI nano and Grimm agreed to within 40% for 5-10 nm particles.展开更多
Understanding the interactions between water and atmospheric aerosols is critical for estimating their impact on the radiation budget and cloud formation. The hygroscopic behavior of ultrafine (〈100nm) ammonium sul...Understanding the interactions between water and atmospheric aerosols is critical for estimating their impact on the radiation budget and cloud formation. The hygroscopic behavior of ultrafine (〈100nm) ammonium sulfate particles internally mixed with either succinic acid (slightly soluble) or levoglucosan (soluble) in different mixing structures (core-shell vs. well-mixed} were measured using a hygroscopicity tandem differential mobility analyzer (HTDMA). During the hydration process (6-92% relative humidity (RH)), the size of core-shell particles (ammonium sulfate and succinic acid) remained unchanged until a slow increase in particle size occurred at 79Y~ RH; however, an abrupt increase in size (i.e., a clear deliquescence) was observed at ~72% RH for well-mixed particles with a similar volume fraction to the core-shell particles (80:20 by volume). This increase might occur because the shell hindered the complete dissolution of the core-shell particles below 92% RH. The onset RH value was lower for the ammonium sulfate/levoglucosan core-shell particles than the ammonium sulfate/succinic acid core-shell particles due to levoglucosan's higher solubility relative to succinic acid. The growth factor (GF) of the core-shell particles was lower than that of the well-mixed particles, while the GF of the ammonium sulfate/levoglucosan particles was higher than that of ammonium sulfate/succinic acid particles with the same volume fractions. As the volume fraction of the organic species increased, the GF decreased. The data suggest that the mixing structure is also important when determining hygroscopic behavior of the mixed particles.展开更多
基金supported by the National Natural Science Foundation of China(No.51975343)Science and Technology Major Project of Inner Mongolia Autonomous Region in China(No.2021ZD0028)+1 种基金Shanghai Technical Service Center for Advanced Ceramics Structure Design and Precision Manufacturing(No.20DZ2294000)the China Scholarship Council.
文摘The material loss caused by bubble collapse during the micro-nano bubbles auxiliary chemical mechanical polishing(CMP)process cannot be ignored.In this study,the material removal mechanism of cavitation in the polishing process was investigated in detail.Based on the mixed lubrication or thin film lubrication,bubble-wafer plastic deformation,spherical indentation theory,Johnson-Cook(J-C)constitutive model,and the assumption of periodic distribution of pad asperities,a new model suitable for micro-nano bubble auxiliary material removal in CMP was developed.The model integrates many parameters,including the reactant concentration,wafer hardness,polishing pad roughness,strain hardening,strain rate,micro-jet radius,and bubble radius.The model reflects the influence of active bubbles on material removal.A new and simple chemical reaction method was used to form a controllable number of micro-nano bubbles during the polishing process to assist in polishing silicon oxide wafers.The experimental results show that micro-nano bubbles can greatly increase the material removal rate(MRR)by about 400%and result in a lower surface roughness of 0.17 nm.The experimental results are consistent with the established model.In the process of verifying the model,a better understanding of the material removal mechanism involved in micro-nano bubbles in CMP was obtained.
基金The research described in this paper was supported by the National Research Foundation of Korea(NRF)Grant Funded by the Korean Government(MEST)(NRF-2011-0015548 and NRF-2010-013-D00034)。
文摘A continuous flow streamwise thermal gradientcloud condensation nuclei(CCN)counter with anaerosol focusing and a laser-charge-coupled device(CCD)camera detector system was developed here.The countingperformance of the laser-CCD camera detector system wasevaluated by comparing its measured number concentrationswith those measured with a condensation particlecounter(CPC)using polystyrene latex(PSL)and NaClparticles of varying sizes.The CCD camera parameters(e.g.brightness,gain,gamma,and exposure time)wereoptimized to detect moving particles in the sensing volumeand to provide the best image to count them.The CCNcounter worked well in the particle number concentrationrange of 0.6-8000#·cm^(-3)and the minimum detectablesize was found to be 0.5μm.The supersaturation in theCCN counter with varying temperature difference wasdetermined by using size-selected sodium chloride particlesbased on Köhler equation.The developed CCNcounter was applied to investigate CCN activity ofatmospheric ultrafine particles at 0.5%supersaturation.Data showed that CCN activity increased with increasingparticle size and that the higher CCN activation forultrafine particles occurred in the afternoon,suggesting thesignificant existence of hygroscopic or soluble species inphotochemically-produced ultrafine particles.
基金supported by the National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MEST)(NRF-2011-0015548)the Basic Research Project through agrant provided by GIST
文摘Three types of water-based condensational growth systems, which can enable particles to grow in size to facilitate sampling and subsequent chemical analysis, were evaluated. The first one is a mixing type growth system where aerosols are mixed with saturated water vapor, the second one is a thermal diffusive growth system where warm flow enters cold-walled tube, and the third one is a laminar flow type where cold flow enters a warm wet-wall tube. Hygroscopic sodium chloride (NaCl), ammonium sulfate ((NH4)2SO4) and ammonium nitrate (NH4N03), and non-hygroscopic polystyrene latex (PSL) particles, in the size range of 50-400 nm, were used to determine their growth factors through the growth systems. Our data showed that the third-type growth system could enable particles to grow most efficiently regardless of their hygroscopic property. Collection efficiency of particles in the size range of 0.05-2.5 μm, in a continuous aerosol sampler after they passed through the third-type growth system was about 100%, suggesting that the third-type growth system would he the most useful among the tested growth systems for sampling and subsequent chemical analysis of fine and ultrafine particles.
基金sponsored by the California Air Resources Board (ARB) under DRI project number 04-307U.S. EPA's Supersites Program at Fresno
文摘Size distributions of ambient aerosols at the Fresno Supersite were measured with four commercially available scanning mobility particle sizers (SMPS). TSI nano, TSI standard, Grimm, and MSP instruments were collocated at the Fresno Supersite and particle size distributions were measured continuously from August 18 through September 18, 2005. For particles with diameters between 10 and 200 nm, differences among hourly-average ambient particle concentrations ranged from 0% between the TSI nano and Grimm in the 30-50 nm size range to 39% between the Grimm and MSP in the 10-30 nm size range. MSP concentrations were 10-33% lower than those measured with the TSI standard for particles smaller than 200 nm. The TSI nano and TSI standard agreed to within 5% in their overlapping size range (10-84 nm). The TSI nano and Grimm agreed to within 40% for 5-10 nm particles.
基金supported by the National Leading Research Laboratory Program funded from the National Research Foundation of Korea (NRF) (No. 2011-0015548)an NRF grant (NRF-C1ABA001-2012-0005668)
文摘Understanding the interactions between water and atmospheric aerosols is critical for estimating their impact on the radiation budget and cloud formation. The hygroscopic behavior of ultrafine (〈100nm) ammonium sulfate particles internally mixed with either succinic acid (slightly soluble) or levoglucosan (soluble) in different mixing structures (core-shell vs. well-mixed} were measured using a hygroscopicity tandem differential mobility analyzer (HTDMA). During the hydration process (6-92% relative humidity (RH)), the size of core-shell particles (ammonium sulfate and succinic acid) remained unchanged until a slow increase in particle size occurred at 79Y~ RH; however, an abrupt increase in size (i.e., a clear deliquescence) was observed at ~72% RH for well-mixed particles with a similar volume fraction to the core-shell particles (80:20 by volume). This increase might occur because the shell hindered the complete dissolution of the core-shell particles below 92% RH. The onset RH value was lower for the ammonium sulfate/levoglucosan core-shell particles than the ammonium sulfate/succinic acid core-shell particles due to levoglucosan's higher solubility relative to succinic acid. The growth factor (GF) of the core-shell particles was lower than that of the well-mixed particles, while the GF of the ammonium sulfate/levoglucosan particles was higher than that of ammonium sulfate/succinic acid particles with the same volume fractions. As the volume fraction of the organic species increased, the GF decreased. The data suggest that the mixing structure is also important when determining hygroscopic behavior of the mixed particles.