Thin sheets (20 μm - 30 μm) of an aluminum-scandium alloy were manufactured by magnetron sputtering with a homogeneous thickness distribution. The influence of bias voltage on the sheet properties was investigated. ...Thin sheets (20 μm - 30 μm) of an aluminum-scandium alloy were manufactured by magnetron sputtering with a homogeneous thickness distribution. The influence of bias voltage on the sheet properties was investigated. Steel sheets of 100 μm were employed as substrate and were coated in a dc magnetron sputtering unit fitted with a rectangular target of aluminum 2.0 w% scandium master alloy. After deposition, the substrates were dissolved in an oxidizing medium and thus freestanding aluminum-scandium thin films were obtained. The homogeneous thickness was achieved by a reciprocal movement of the substrate. The influence of a radio frequency bias voltage on the coating properties was investigated. The bias voltage resulted in an important coarsening of the columnar structure as well as an increase of the roughness and hardness. Additionally, a low bias voltage could intensively reduce the coating defect density without altering too much the sheet properties.展开更多
Existing auto-focusing methods in laser processing typically include two independent modules,one for surface detection and another for z-axis adjustment.The latter is mostly implemented by mechanical z stage motion,wh...Existing auto-focusing methods in laser processing typically include two independent modules,one for surface detection and another for z-axis adjustment.The latter is mostly implemented by mechanical z stage motion,which is up to three orders of magnitude slower than the lateral processing speed.To alleviate this processing bottleneck,we developed a single-lens approach,using only one high-speed z-scanning optical element,to accomplish both in situ surface detection and focus control quasi-simultaneously in a dual-beam setup.The probing beam scans the surface along the z-axis continuously,and its reflection is detected by a set of confocal optics.Based on the temporal response of the detected signal,we have developed and experimentally demonstrated a dynamic surface detection method at 140-350 kHz,with a controlled detection range,high repeatability,and minimum linearity error of 1.10%.Sequentially,by synchronizing at a corresponding oscillation phase of the z-scanning lens,the fabrication beam is directed to the probed z position for precise focus alignment.Overall,our approach provides instantaneous surface tracking by collecting position information and executing focal control both at 140-350 kHz,which significantly accelerates the axial alignment process and offers great potential for enhancing the speed of advanced manufacturing processes in three-dimensional space.展开更多
Observing the motion of electrons on their natural nanometer length and femtosecond time scales is a fundamental goal of and an open challenge for contemporary ultrafast science1–5.At present,optical techniques and e...Observing the motion of electrons on their natural nanometer length and femtosecond time scales is a fundamental goal of and an open challenge for contemporary ultrafast science1–5.At present,optical techniques and electron microscopy mostly provide either ultrahigh temporal or spatial resolution,and microscopy techniques with combined space-time resolution require further development6–11.In this study,we create an ultrafast electron source via plasmon nanofocusing on a sharp gold taper and implement this source in an ultrafast point-projection electron microscope.This source is used in an optical pump—electron probe experiment to study ultrafast photoemissions from a nanometer-sized plasmonic antenna12–15.We probe the real space motion of the photoemitted electrons with a 20-nm spatial resolution and a 25-fs time resolution and reveal the deflection of probe electrons by residual holes in the metal.This is a step toward time-resolved microscopy of electronic motion in nanostructures.展开更多
We report long-lived,highly spatially localized plasmon states on the surface of nanoporous gold nanoparticles—nanosponges—with high excitation efficiency.It is well known that disorder on the nanometer scale,partic...We report long-lived,highly spatially localized plasmon states on the surface of nanoporous gold nanoparticles—nanosponges—with high excitation efficiency.It is well known that disorder on the nanometer scale,particularly in two-dimensional systems,can lead to plasmon localization and large field enhancements,which can,in turn,be used to enhance nonlinear optical effects and to study and exploit quantum optical processes.Here,we introduce promising,three-dimensional model systems for light capture and plasmon localization as gold nanosponges that are formed by the dewetting of gold/silver bilayers and dealloying.We study light-induced electron emission from single nanosponges,a nonlinear process with exponents of n≈5...7,using ultrashort laser pulse excitation to achieve femtosecond time resolution.The long-lived electron emission process proves,in combination with optical extinction measurements and finite-difference time-domain calculations,the existence of localized modes with lifetimes of more than 20 fs.These electrons couple efficiently to the dipole antenna mode of each individual nanosponge,which in turn couples to the far-field.Thus,individual gold nanosponges are cheap and robust disordered nanoantennas with strong local resonances,and an ensemble of nanosponges constitutes a meta material with a strong polarization independent,nonlinear response over a wide frequency range.展开更多
文摘Thin sheets (20 μm - 30 μm) of an aluminum-scandium alloy were manufactured by magnetron sputtering with a homogeneous thickness distribution. The influence of bias voltage on the sheet properties was investigated. Steel sheets of 100 μm were employed as substrate and were coated in a dc magnetron sputtering unit fitted with a rectangular target of aluminum 2.0 w% scandium master alloy. After deposition, the substrates were dissolved in an oxidizing medium and thus freestanding aluminum-scandium thin films were obtained. The homogeneous thickness was achieved by a reciprocal movement of the substrate. The influence of a radio frequency bias voltage on the coating properties was investigated. The bias voltage resulted in an important coarsening of the columnar structure as well as an increase of the roughness and hardness. Additionally, a low bias voltage could intensively reduce the coating defect density without altering too much the sheet properties.
基金funding from Princeton University(Eric and Wendy Schmidt Fund,DG5709)C.F.acknowledges the funding from European Commission(Marie Curie Fellowship IF,FOCUSIS,Grant Agreement 844977).
文摘Existing auto-focusing methods in laser processing typically include two independent modules,one for surface detection and another for z-axis adjustment.The latter is mostly implemented by mechanical z stage motion,which is up to three orders of magnitude slower than the lateral processing speed.To alleviate this processing bottleneck,we developed a single-lens approach,using only one high-speed z-scanning optical element,to accomplish both in situ surface detection and focus control quasi-simultaneously in a dual-beam setup.The probing beam scans the surface along the z-axis continuously,and its reflection is detected by a set of confocal optics.Based on the temporal response of the detected signal,we have developed and experimentally demonstrated a dynamic surface detection method at 140-350 kHz,with a controlled detection range,high repeatability,and minimum linearity error of 1.10%.Sequentially,by synchronizing at a corresponding oscillation phase of the z-scanning lens,the fabrication beam is directed to the probed z position for precise focus alignment.Overall,our approach provides instantaneous surface tracking by collecting position information and executing focal control both at 140-350 kHz,which significantly accelerates the axial alignment process and offers great potential for enhancing the speed of advanced manufacturing processes in three-dimensional space.
基金the Deutsche Forschungsgemeinschaft for support within the priority program QUTIF(SPP1840)support from SPP1839,the German-Israeli Foundation(GIF grant no.1256)+2 种基金the Korea Foundation for International Cooperation of Science and Technology(Global Research Laboratory project,K20815000003)is acknowledgedthe HPC Cluster CARL in Oldenburg(DFG INST 184/157-1 FUGG)the Studienstiftung des Deutschen Volkes for the personal grant.
文摘Observing the motion of electrons on their natural nanometer length and femtosecond time scales is a fundamental goal of and an open challenge for contemporary ultrafast science1–5.At present,optical techniques and electron microscopy mostly provide either ultrahigh temporal or spatial resolution,and microscopy techniques with combined space-time resolution require further development6–11.In this study,we create an ultrafast electron source via plasmon nanofocusing on a sharp gold taper and implement this source in an ultrafast point-projection electron microscope.This source is used in an optical pump—electron probe experiment to study ultrafast photoemissions from a nanometer-sized plasmonic antenna12–15.We probe the real space motion of the photoemitted electrons with a 20-nm spatial resolution and a 25-fs time resolution and reveal the deflection of probe electrons by residual holes in the metal.This is a step toward time-resolved microscopy of electronic motion in nanostructures.
基金support by the Deutsche Forschungsgemeinschaft(SPP1839‘Tailored Disorder’,grants LI 580/12,RU 1383/5,SCHA 632/24)the Korea Foundation for the International Cooperation of Science and Technology(Global Research Laboratory project,K20815000003)+1 种基金the German-Israeli Foundation(GIF Grant No.1256)is gratefully acknowledgeda personal grant from the Studienstiftung des Deutschen Volkes.
文摘We report long-lived,highly spatially localized plasmon states on the surface of nanoporous gold nanoparticles—nanosponges—with high excitation efficiency.It is well known that disorder on the nanometer scale,particularly in two-dimensional systems,can lead to plasmon localization and large field enhancements,which can,in turn,be used to enhance nonlinear optical effects and to study and exploit quantum optical processes.Here,we introduce promising,three-dimensional model systems for light capture and plasmon localization as gold nanosponges that are formed by the dewetting of gold/silver bilayers and dealloying.We study light-induced electron emission from single nanosponges,a nonlinear process with exponents of n≈5...7,using ultrashort laser pulse excitation to achieve femtosecond time resolution.The long-lived electron emission process proves,in combination with optical extinction measurements and finite-difference time-domain calculations,the existence of localized modes with lifetimes of more than 20 fs.These electrons couple efficiently to the dipole antenna mode of each individual nanosponge,which in turn couples to the far-field.Thus,individual gold nanosponges are cheap and robust disordered nanoantennas with strong local resonances,and an ensemble of nanosponges constitutes a meta material with a strong polarization independent,nonlinear response over a wide frequency range.
