5 research outputs found
Electron bunch generation from a plasma photocathode
Plasma waves generated in the wake of intense, relativistic laser or particle
beams can accelerate electron bunches to giga-electronvolt (GeV) energies in
centimetre-scale distances. This allows the realization of compact accelerators
having emerging applications, ranging from modern light sources such as the
free-electron laser (FEL) to energy frontier lepton colliders. In a plasma
wakefield accelerator, such multi-gigavolt-per-metre (GV m) wakefields
can accelerate witness electron bunches that are either externally injected or
captured from the background plasma. Here we demonstrate optically triggered
injection and acceleration of electron bunches, generated in a multi-component
hydrogen and helium plasma employing a spatially aligned and synchronized laser
pulse. This ''plasma photocathode'' decouples injection from wake excitation by
liberating tunnel-ionized helium electrons directly inside the plasma cavity,
where these cold electrons are then rapidly boosted to relativistic velocities.
The injection regime can be accessed via optical density down-ramp injection,
is highly tunable and paves the way to generation of electron beams with
unprecedented low transverse emittance, high current and 6D-brightness. This
experimental path opens numerous prospects for transformative plasma wakefield
accelerator applications based on ultra-high brightness beams
Epitaxial ALD BeO: Efficient Oxygen Diffusion Barrier for EOT Scaling and Reliability Improvement
In a previous study, we demonstrated that the BeO film grown by atomic layer deposition (ALD) on Si and III-V metal-oxide-semiconductor devices has excellent electrical and physical characteristics. In this paper, we discuss the physical and electrical properties of ALD BeO as an oxygen diffusion barrier on scaled 4-nm HfO2/BeO gate stacks. Thin BeO layers are deposited onto (100) p-Si substrates as an alternative to SiO2 as an interfacial passivation layer (IPL). X-ray photoelectron spectroscopy and transmission electron microscopy show that the BeO IPL acts as an effective oxygen barrier against SiOx native oxide formation during postdeposition annealing (PDA). The use of ALD BeO as an oxygen diffusion barrier results in lower equivalent oxide thickness, more competitive leakage current, and better reliability characteristics after PDA than Al2O3 and HfO2 gate stacks
Recommended from our members
Electron bunch generation from a plasma photocathode
Plasma waves generated in the wake of intense, relativistic laser or particle
beams can accelerate electron bunches to giga-electronvolt (GeV) energies in
centimetre-scale distances. This allows the realization of compact accelerators
having emerging applications, ranging from modern light sources such as the
free-electron laser (FEL) to energy frontier lepton colliders. In a plasma
wakefield accelerator, such multi-gigavolt-per-metre (GV m) wakefields
can accelerate witness electron bunches that are either externally injected or
captured from the background plasma. Here we demonstrate optically triggered
injection and acceleration of electron bunches, generated in a multi-component
hydrogen and helium plasma employing a spatially aligned and synchronized laser
pulse. This ''plasma photocathode'' decouples injection from wake excitation by
liberating tunnel-ionized helium electrons directly inside the plasma cavity,
where these cold electrons are then rapidly boosted to relativistic velocities.
The injection regime can be accessed via optical density down-ramp injection,
is highly tunable and paves the way to generation of electron beams with
unprecedented low transverse emittance, high current and 6D-brightness. This
experimental path opens numerous prospects for transformative plasma wakefield
accelerator applications based on ultra-high brightness beams
2020 roadmap on plasma accelerators
Plasma-based accelerators use the strong electromagnetic fields that can be supported by plasmasto accelerate charged particles to high energies. Accelerating field structures in plasma can begenerated by powerful laser pulses or charged particle beams. This research field has recentlytransitioned from involving a few small-scale efforts to the development of national andinternational networks of scientists supported by substantial investment in large-scale researchinfrastructure. In this New Journal of Physics 2020 Plasma Accelerator Roadmap, perspectivesfrom experts in this field provide a summary overview of the field and insights into the researchneeds and developments for an international audience of scientists, including graduate studentsand researchers entering the field