This paper describes the realization of a homogeneous dielectric barrier discharge(DBD)in argon at atmospheric pressure.The effect of the morphology of the dielectric surface(especially the dielectric surface covered ...This paper describes the realization of a homogeneous dielectric barrier discharge(DBD)in argon at atmospheric pressure.The effect of the morphology of the dielectric surface(especially the dielectric surface covered by hollow ceramic beads(99%Al_(2)O_(3))with different diameters)on discharge is investigated.With different dielectrics,the argon DBD presents two discharge modes:a filamentary mode and a homogeneous mode.Fast photography shows that the filamentary mode operates in a streamer discharge,and the homogeneous mode operates in a Townsend discharge regime.It is found that a homogeneous discharge can be generated within a certain voltage range.The voltage amplitude range decreases,and the breakdown voltage increases with the increase in the mean diameter of the ceramic beads.Waveforms of the total current and optical emission signal present stochastic pulses per half voltage cycle for the filamentary mode,whereas there is one single hump per half voltage cycle for the homogeneous mode.In the homogeneous mode,the intensity of the optical emission decreases with the mean diameter of the ceramic beads.The optical emission spectrum is mainly composed of atomic lines of argon and the second positive system of molecular nitrogen.It reveals that the electron density decreases with the increasing mean diameter of the ceramic beads.The vibrational temperature increases with the increasing mean diameter of the ceramic beads.It is believed that a large number of microdischarges are formed,and smaller ceramic beads have a larger activation surface area and more point discharge.Electrons liberated in the shallow well and electrons generated from microdischarges can increase the secondary electron emission coefficient of the cathode and provide initial electrons for discharge continuously.Therefore,the breakdown electric field is reduced,which contributes to easier generation of homogeneous discharge.This is confirmed by the simulation results.展开更多
The epitaxial-Si（epi-Si） growth on the crystalline Si（c-Si） wafer could be tailored by the working pressure in plasmaenhanced chemical vapor deposition（PECVD）.It has been systematically confirmed that the epitax...The epitaxial-Si（epi-Si） growth on the crystalline Si（c-Si） wafer could be tailored by the working pressure in plasmaenhanced chemical vapor deposition（PECVD）.It has been systematically confirmed that the epitaxial growth at the hydrogenated amorphous silicon（a-Si：H）/c-Si interface is suppressed at high pressure（hp） and occurs at low pressure（1p）.The hp a-Si：H,as a purely amorphous layer,is incorporated in the 1p-epi-Si/c-Si interface.We find that：（i） the epitaxial growth can also occur at a-Si：H coated c-Si wafer as long as this amorphous layer is thin enough;（ii） with the increase of the inserted hp layer thickness,lp epi-Si at the interface is suppressed,and the fraction of a-Si：H in the thin films increases and that of c-Si decreases,corresponding to the increasing minority carrier lifetime of the sample.Not only the epitaxial results,but also the quality of the thin films at hp also surpasses that at lp,leading to the longer minority carrier lifetime of the hp sample than the lp one although they have the same amorphous phase.展开更多
基金supported by National Natural Science Foundation of China(Nos.11875121,51977057,11575050,11875014)the Hebei Province Natural Science Foundation(No.A2022201036)。
文摘This paper describes the realization of a homogeneous dielectric barrier discharge(DBD)in argon at atmospheric pressure.The effect of the morphology of the dielectric surface(especially the dielectric surface covered by hollow ceramic beads(99%Al_(2)O_(3))with different diameters)on discharge is investigated.With different dielectrics,the argon DBD presents two discharge modes:a filamentary mode and a homogeneous mode.Fast photography shows that the filamentary mode operates in a streamer discharge,and the homogeneous mode operates in a Townsend discharge regime.It is found that a homogeneous discharge can be generated within a certain voltage range.The voltage amplitude range decreases,and the breakdown voltage increases with the increase in the mean diameter of the ceramic beads.Waveforms of the total current and optical emission signal present stochastic pulses per half voltage cycle for the filamentary mode,whereas there is one single hump per half voltage cycle for the homogeneous mode.In the homogeneous mode,the intensity of the optical emission decreases with the mean diameter of the ceramic beads.The optical emission spectrum is mainly composed of atomic lines of argon and the second positive system of molecular nitrogen.It reveals that the electron density decreases with the increasing mean diameter of the ceramic beads.The vibrational temperature increases with the increasing mean diameter of the ceramic beads.It is believed that a large number of microdischarges are formed,and smaller ceramic beads have a larger activation surface area and more point discharge.Electrons liberated in the shallow well and electrons generated from microdischarges can increase the secondary electron emission coefficient of the cathode and provide initial electrons for discharge continuously.Therefore,the breakdown electric field is reduced,which contributes to easier generation of homogeneous discharge.This is confirmed by the simulation results.
基金Project supported by the Natural Science Foundation of Hebei Province,China(Grant No.E2015201203)the International Society for Theoretical Chemical Physics of China(Grant No.2015DFE62900)
文摘The epitaxial-Si（epi-Si） growth on the crystalline Si（c-Si） wafer could be tailored by the working pressure in plasmaenhanced chemical vapor deposition（PECVD）.It has been systematically confirmed that the epitaxial growth at the hydrogenated amorphous silicon（a-Si：H）/c-Si interface is suppressed at high pressure（hp） and occurs at low pressure（1p）.The hp a-Si：H,as a purely amorphous layer,is incorporated in the 1p-epi-Si/c-Si interface.We find that：（i） the epitaxial growth can also occur at a-Si：H coated c-Si wafer as long as this amorphous layer is thin enough;（ii） with the increase of the inserted hp layer thickness,lp epi-Si at the interface is suppressed,and the fraction of a-Si：H in the thin films increases and that of c-Si decreases,corresponding to the increasing minority carrier lifetime of the sample.Not only the epitaxial results,but also the quality of the thin films at hp also surpasses that at lp,leading to the longer minority carrier lifetime of the hp sample than the lp one although they have the same amorphous phase.
