First mirrors（FMs） are crucial components of optical diagnostic systems in present-day tokamaks and future fusion reactors. Their lifetimes should be extremely limited due to their proximity to burning plasma, great...First mirrors（FMs） are crucial components of optical diagnostic systems in present-day tokamaks and future fusion reactors. Their lifetimes should be extremely limited due to their proximity to burning plasma, greatly influencing the safe operation of corresponding diagnostics.Repetitive cleaning is expected to provide a solution to the frequent replacement of contaminated FMs, thus prolonging their lifetimes. Three repetitive cleaning cycles using radio frequency plasma were applied to stainless steel（SS） FM samples, to evaluate the change of the mirrors＇ optical properties and morphology during each cycle. Amorphous carbon films were deposited on mirror surfaces under identical conditions in three cycles. In three cycles with identical cleaning parameters, the total reflectivity was restored at up to 95%. Nevertheless, with successive cleaning cycles, the FM surfaces gradually appeared to roughen due to damage to the grain boundaries. Correspondingly, the diffuse reflectivity increased from a few percent to 20%and 27% after the second and third cycles. After optimizing the cleaning parameters of the second and third cycles, the roughness showed a significant decrease, and simultaneously the increase of diffuse reflectivity was remarkably improved.展开更多
Introducing defects into graphene has been widely utilized to realize the negative magnetoresistanee(MR)effect in graphene.However,the reported graphene negative MR exhibits only^10%under 10 T at room temperature to d...Introducing defects into graphene has been widely utilized to realize the negative magnetoresistanee(MR)effect in graphene.However,the reported graphene negative MR exhibits only^10%under 10 T at room temperature to date,which extremely limits the resolution of future spintronics devices.Moreover,intentional defect introduction can also cause unintentional degradation in graphene's intrinsic properties.In this paper,we report a magnetic logic inverter based on a crossed structure of defect-free graphene,resulting in a substantial gain of 4.81 mV/T while exhibiting room temperature operation.This crossed structure of graphene shows large unsaturated room temperature negative MR with an enhancement of up to 1,000%at 9 T.A transition behavior between negative and positive MR is observed in this crossed structure and the transition temperature can be tuned by a ratio of the conductivity between in-plane and out-of-plane transport.Our results open an intriguing path for future two-dimensional spintronics device applications.展开更多
基金supported by National Magnetic Confinement Fusion Science Program of China under Contract Nos. 2013GB105003 and 2013GB107004National Natural Science Foundation of China under Contract Nos. 11475218, 11505231, 11375010 and 11675218
文摘First mirrors（FMs） are crucial components of optical diagnostic systems in present-day tokamaks and future fusion reactors. Their lifetimes should be extremely limited due to their proximity to burning plasma, greatly influencing the safe operation of corresponding diagnostics.Repetitive cleaning is expected to provide a solution to the frequent replacement of contaminated FMs, thus prolonging their lifetimes. Three repetitive cleaning cycles using radio frequency plasma were applied to stainless steel（SS） FM samples, to evaluate the change of the mirrors＇ optical properties and morphology during each cycle. Amorphous carbon films were deposited on mirror surfaces under identical conditions in three cycles. In three cycles with identical cleaning parameters, the total reflectivity was restored at up to 95%. Nevertheless, with successive cleaning cycles, the FM surfaces gradually appeared to roughen due to damage to the grain boundaries. Correspondingly, the diffuse reflectivity increased from a few percent to 20%and 27% after the second and third cycles. After optimizing the cleaning parameters of the second and third cycles, the roughness showed a significant decrease, and simultaneously the increase of diffuse reflectivity was remarkably improved.
基金This work was supported by the National Natural Science Foundation Committee of the China Academy of Engineering Physics(NSAF)(No.U1630108)the joint fund of the National Key Research and Development Program of China(No.2017YFA0402902)+1 种基金the National Natural Science Foundation of China(No.11434009)This research was partially carried out at the USTC Center for Micro and Nanoscale Research and Fabrication.
文摘Introducing defects into graphene has been widely utilized to realize the negative magnetoresistanee(MR)effect in graphene.However,the reported graphene negative MR exhibits only^10%under 10 T at room temperature to date,which extremely limits the resolution of future spintronics devices.Moreover,intentional defect introduction can also cause unintentional degradation in graphene's intrinsic properties.In this paper,we report a magnetic logic inverter based on a crossed structure of defect-free graphene,resulting in a substantial gain of 4.81 mV/T while exhibiting room temperature operation.This crossed structure of graphene shows large unsaturated room temperature negative MR with an enhancement of up to 1,000%at 9 T.A transition behavior between negative and positive MR is observed in this crossed structure and the transition temperature can be tuned by a ratio of the conductivity between in-plane and out-of-plane transport.Our results open an intriguing path for future two-dimensional spintronics device applications.
