Atmospheric-pressure argon plasmas have received increasing attention due to their high potential in many industrial and biomedical applications. In this paper, a 1-D fluid model is used for studying the particle dens...Atmospheric-pressure argon plasmas have received increasing attention due to their high potential in many industrial and biomedical applications. In this paper, a 1-D fluid model is used for studying the particle density characteristics of the argon plasmas generated by the pulsed dielectric barrier discharges. The temporal evolutions of the axial particle density distributions are illustrated, and the influences of changing the main discharge conditions on the averaged particle densities are researched by independently varying the various discharge conditions. The calculation results show that the electron density and the ion density reach two peaks near the momentary cathodes during the rising and the falling edges of the pulsed voltage. Compared with the charged particle densities, the densities of the resonance state atom Arr and the metastable state atom Arm have more uniform axial distributions, reach higher maximums and decay more slowly. During the platform of the pulsed voltage and the time interval between the pulses, the densities of the excited state atom Ar＊ are far lower than those of the Arr or the Arm. The averaged particle densities of the different considered particles increase with the increases of the amplitude and the frequency of the pulsed voltage. Narrowing the discharge gap and increasing the relative dielectric constant of the dielectric also contribute to the increase of the averaged particle densities. The effects of reducing the discharge gap distance on the neutral particle densities are more significant than the influences on the charged particle densities.展开更多
We report an out-of-plane magnetic field induced large photoluminescence enhancement in WS2 flakes at 4K,in contrast to the photoluminescence enhancement provided by an in-plane field in general.Two mechanisms for the...We report an out-of-plane magnetic field induced large photoluminescence enhancement in WS2 flakes at 4K,in contrast to the photoluminescence enhancement provided by an in-plane field in general.Two mechanisms for the enhancement are proposed.One is a larger overlap of the electron and hole caused by the magnetic field induced confinement.The other is that the energy difference between varLambda and K valleys is reduced by magnetic field,and thus enhancing the corresponding indirect-transition trions.Meanwhile,the Landé g factor of the trion is measured to be-0.8,whose absolute value is much smaller than normal exciton,which is around-4.A model for the trion gfactor is presented,confirming that the smaller absolute value of the Landé g factor is a behavior of this A–Ktrion.By extending the valley space,we believe this work provides a further understanding of the valleytronics in monolayer transition metal dichalcogenides.展开更多
基金supported by Natural Science Foundation of Shandong Province,China(No.ZR2015AQ008)Project of Shandong Province Higher Educational Science and Technology Program of China(No.J15LJ04)
文摘Atmospheric-pressure argon plasmas have received increasing attention due to their high potential in many industrial and biomedical applications. In this paper, a 1-D fluid model is used for studying the particle density characteristics of the argon plasmas generated by the pulsed dielectric barrier discharges. The temporal evolutions of the axial particle density distributions are illustrated, and the influences of changing the main discharge conditions on the averaged particle densities are researched by independently varying the various discharge conditions. The calculation results show that the electron density and the ion density reach two peaks near the momentary cathodes during the rising and the falling edges of the pulsed voltage. Compared with the charged particle densities, the densities of the resonance state atom Arr and the metastable state atom Arm have more uniform axial distributions, reach higher maximums and decay more slowly. During the platform of the pulsed voltage and the time interval between the pulses, the densities of the excited state atom Ar＊ are far lower than those of the Arr or the Arm. The averaged particle densities of the different considered particles increase with the increases of the amplitude and the frequency of the pulsed voltage. Narrowing the discharge gap and increasing the relative dielectric constant of the dielectric also contribute to the increase of the averaged particle densities. The effects of reducing the discharge gap distance on the neutral particle densities are more significant than the influences on the charged particle densities.
基金Supported by the National Natural Science Foundation of China(Grants Nos.11934019,61675228,11721404,51761145104 and 11874419)the Strategic Priority Research Program,the Instrument Developing Project and the Interdisciplinary Innovation Team of the Chinese Academy of Sciences(Grant Nos.XDB28000000 and YJKYYQ20180036)the Key Research and Development Program of Guangdong Province(Grant No.2018B030329001).
文摘We report an out-of-plane magnetic field induced large photoluminescence enhancement in WS2 flakes at 4K,in contrast to the photoluminescence enhancement provided by an in-plane field in general.Two mechanisms for the enhancement are proposed.One is a larger overlap of the electron and hole caused by the magnetic field induced confinement.The other is that the energy difference between varLambda and K valleys is reduced by magnetic field,and thus enhancing the corresponding indirect-transition trions.Meanwhile,the Landé g factor of the trion is measured to be-0.8,whose absolute value is much smaller than normal exciton,which is around-4.A model for the trion gfactor is presented,confirming that the smaller absolute value of the Landé g factor is a behavior of this A–Ktrion.By extending the valley space,we believe this work provides a further understanding of the valleytronics in monolayer transition metal dichalcogenides.
