- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Controlled strong excitation of silicon as a step towards processing materials at sub-nanometer precision
摘要： Interaction of a solid material with focused, intense pulses of high-energy photons or other particles (such as electrons and ions) creates a strong electronic excitation state within an ultra-short time and on ultra-small spatial scales. This offers the possibility to control the response of a material on a spatial scale less than a nanometer—crucial for the next generation of nano-devices. Here we create craters on the surface of a silicon substrate by focusing single femtosecond extreme ultraviolet pulse from the SACLA free-electron laser. We investigate the resulting surface modification in the vicinity of damage thresholds, establishing a connection to microscopic theoretical approaches, and, with their help, illustrating physical mechanisms for damage creation. The cooling during ablation by means of rapid electron and energy transport can suppress undesired hydrodynamical motions, allowing the silicon material to be directly processed with a precision reaching the observable limitation of an atomic force microscope.
关键词： nanometer precision,ablation,extreme ultraviolet,femtosecond,silicon,free-electron laser
更新于2025-09-11 14:15:04
-
Reference Module in Materials Science and Materials Engineering || Optical Lithography
摘要： Optical lithography is a photon-based technique comprised of projecting, or shadow casting, an image into a photosensitive emulsion (photoresist) coated onto the substrate of choice. Today it is the most widely used lithography process in the manufacturing of nano-electronics by the semiconductor industry, a $400 Billion industry worldwide. Optical lithography’s ubiquitous use is a direct result of its highly parallel nature allowing vast amounts of information (i.e., patterns) to be transferred in a very short time. For example, considering the specification of a modern leading edge scanner (150–300-mm wafers per hour and 40-nm two-dimensional pattern resolution), the pixel throughput can be found to be approximately 1.8T pixels per second. Continual advances in optical lithography capabilities have enabled the computing revolution we have undergone over the past 50 years.
关键词： Nano-electronics,Numerical Aperture (NA),Coherence,Resolution,Photoresist,Depth of Focus (DOF),Optical Lithography,Extreme Ultraviolet (EUV),Semiconductor
更新于2025-09-10 09:29:36
-
ions
摘要： Laser-produced Sn plasma sources are used to generate extreme ultraviolet light in state-of-the-art nanolithography. An ultraviolet and optical spectrum is measured from a droplet-based laser-produced Sn plasma, with a spectrograph covering the range 200–800 nm. This spectrum contains hundreds of spectral lines from lowly charged tin ions Sn1+?Sn4+ of which a major fraction was hitherto unidenti?ed. We present and identify a selected class of lines belonging to the quasi-one-electron, Ag-like ([Kr]4d 10 nl electronic con?guration), Sn3+ ion, linking the optical lines to a speci?c charge state by means of a masking technique. These line identi?cations are made with iterative guidance from COWAN code calculations. Of the 53 lines attributed to Sn3+, some 20 were identi?ed from previously known energy levels, and 33 lines are used to determine previously unknown level energies of 13 electronic con?gurations, i.e., 7p, (7, 8)d, (5, 6)f , (6–8)g, (6–8)h, (7, 8)i. The consistency of the level energy determination is veri?ed by the quantum-defect scaling procedure. The ionization limit of Sn3+ is con?rmed and re?ned to 328 908.4 cm?1, with an uncertainty of 2.1 cm?1. The relativistic Fock-space coupled-cluster (FSCC) calculations of the measured level energies are generally in good agreement with experiment but fail to reproduce the anomalous behavior of the 5d 2D and nf 2F terms. By combining the strengths of the FSCC calculations, COWAN code calculations, and con?guration interaction many-body perturbation theory, this behavior is shown to arise from interactions with doubly excited con?gurations.
关键词： Sn3+ ions,energy-level structure,nanolithography,laser-produced plasma,extreme ultraviolet light
更新于2025-09-09 09:28:46
-
Measurements of the effective electron density in an electron beam ion trap using extreme ultraviolet spectra and optical imaging
摘要： In an electron beam ion trap (EBIT), the ions are not con?ned to the electron beam, but rather oscillate in and out of the beam. As a result, the ions do not continuously experience the full density of the electron beam. To determine the effective electron density, ne,eff, experienced by the ions, the electron beam size, the nominal electron density ne, and the ion distribution around the beam, i.e., the so-called ion cloud, must be measured. We use imaging techniques in the extreme ultraviolet (EUV) and optical to determine these. The electron beam width is measured using 3d → 3p emission from Fe xii and xiii between 185 and 205 ?. These transitions are fast and the EUV emission occurs only within the electron beam. The measured spatial emission pro?le and variable electron current yield a nominal electron density range of ne ～ 1011–1013 cm?3. We determine the size of the ion cloud using optical emission from metastable levels of ions with radiative lifetimes longer than the ion orbital periods. The resulting emission maps out the spatial distribution of the ion cloud. We ?nd a typical electron beam radius of ～60 μm and an ion cloud radius of ～300 μm. These yield a spatially averaged effective electron density, ne,eff, experienced by the ions in EBIT spanning ～ 5 × 109–5 × 1011 cm?3.
关键词： optical imaging,effective electron density,extreme ultraviolet spectra,electron beam ion trap,Fe xiv,Fe xiii,Fe xii
更新于2025-09-09 09:28:46
-
A comprehensive three-dimensional radiative magnetohydrodynamic simulation of a solar flare
摘要： Solar and stellar flares are the most intense emitters of X-rays and extreme ultraviolet radiation in planetary systems. On the Sun, strong flares are usually found in newly emerging sunspot regions. The emergence of these magnetic sunspot groups leads to the accumulation of magnetic energy in the corona. When the magnetic field undergoes abrupt relaxation, the energy released powers coronal mass ejections as well as heating plasma to temperatures beyond tens of millions of kelvins. While recent work has shed light on how magnetic energy and twist accumulate in the corona and on how three-dimensional magnetic reconnection allows for rapid energy release, a self-consistent model capturing how such magnetic changes translate into observable diagnostics has remained elusive. Here, we present a comprehensive radiative magnetohydrodynamics simulation of a solar flare capturing the process from emergence to eruption. The simulation has sufficient realism for the synthesis of remote sensing measurements to compare with observations at visible, ultraviolet and X-ray wavelengths. This unifying model allows us to explain a number of well-known features of solar flares, including the time profile of the X-ray flux during flares, origin and temporal evolution of chromospheric evaporation and condensation, and sweeping of flare ribbons in the lower atmosphere. Furthermore, the model reproduces the apparent non-thermal shape of coronal X-ray spectra, which is the result of the superposition of multi-component super-hot plasmas up to and beyond 100 million K.
关键词： extreme ultraviolet radiation,solar flares,X-rays,magnetohydrodynamics,coronal mass ejections
更新于2025-09-09 09:28:46
-
Vortex Dynamics and Optical Vortices || Ultrashort Extreme Ultraviolet Vortices
摘要： Optical vortices are very attractive because they transport a well-defined orbital angular momentum (OAM) associated with the singularity of the beam. These singular beams, commonly generated in the optical regime, are used in a wide range of applications: communication, micromanipulation, microscopy, among others. The production of OAM beams in the extreme ultraviolet (XUV) and X-ray regimes is of great interest as it allows to extend the applications of optical vortices down to the nanometric scale. Several proposals have been explored in order to generate XUV vortices in synchrotrons and FEL facilities. Here, we study the generation of XUV vortices through high-order harmonic generation (HHG). HHG is a unique source of coherent radiation extending from the XUV to the soft X-ray regime, emitted in the form of attosecond pulses. When driving HHG by OAM beams, highly charged XUV vortices with unprecedented spatiotemporal properties are emitted in the form of helical attosecond beams. In this chapter, we revise our theoretical work in the generation of XUV vortices by HHG. In particular, we illustrate in detail the role of macroscopic phase matching of high-order harmonics when driven by OAM beams, which allows to control the production of attosecond beams carrying OAM.
关键词： attosecond helical beams,ultrafast phenomena,orbital angular momentum,attosecond pulses,extreme ultraviolet vortices,high harmonic generation,nonlinear optics,phase matching
更新于2025-09-09 09:28:46
-
Extreme-ultraviolet refractive optics
摘要： Refraction is a well-known optical phenomenon that alters the direction of light waves propagating through matter. Microscopes, lenses and prisms based on refraction are indispensable tools for controlling light beams at visible, infrared, ultraviolet and X-ray wavelengths1. In the past few decades, a range of extreme- ultraviolet and soft-X-ray sources has been developed in laboratory environments2–4 and at large-scale facilities5,6. But the strong absorption of extreme-ultraviolet radiation in matter hinders the development of refractive lenses and prisms in this spectral region, for which reflective mirrors and diffractive Fresnel zone plates7 are instead used for focusing. Here we demonstrate control over the refraction of extreme- ultraviolet radiation by using a gas jet with a density gradient across the profile of the extreme-ultraviolet beam. We produce a gas- phase prism that leads to a frequency-dependent deflection of the beam. The strong deflection near to atomic resonances is further used to develop a deformable refractive lens for extreme-ultraviolet radiation, with low absorption and a focal length that can be tuned by varying the gas pressure. Our results open up a route towards the transfer of refraction-based techniques, which are well established in other spectral regions, to the extreme-ultraviolet domain.
关键词： lens,refractive optics,extreme-ultraviolet,prism,gas jet
更新于2025-09-09 09:28:46
-
Controlling the polarization and vortex charge of attosecond high-harmonic beams via simultaneous spin–orbit momentum conservation
摘要： Optical interactions are governed by both spin and angular momentum conservation laws, which serve as a tool for controlling light–matter interactions or elucidating electron dynamics and structure of complex systems. Here, we uncover a form of simultaneous spin and orbital angular momentum conservation and show, theoretically and experimentally, that this phenomenon allows for unprecedented control over the divergence and polarization of extreme-ultraviolet vortex beams. High harmonics with spin and orbital angular momenta are produced, opening a novel regime of angular momentum conservation that allows for manipulation of the polarization of attosecond pulses—from linear to circular—and for the generation of circularly polarized vortices with tailored orbital angular momentum, including harmonic vortices with the same topological charge as the driving laser beam. Our work paves the way to ultrafast studies of chiral systems using high-harmonic beams with designer spin and orbital angular momentum.
关键词： attosecond high-harmonic beams,polarization control,vortex charge,spin–orbit momentum conservation,extreme-ultraviolet vortex beams
更新于2025-09-04 15:30:14
-
Focal overlap gating in velocity map imaging to achieve high signal-to-noise ratio in photo-ion pump-probe experiments
摘要： We demonstrate a technique in velocity map imaging (VMI) that allows spatial gating of the laser focal overlap region in time resolved pump-probe experiments. This significantly enhances signal-to-noise ratio by eliminating background signal arising outside the region of spatial overlap of pump and probe beams. This enhancement is achieved by tilting the laser beams with respect to the surface of the VMI electrodes which creates a gradient in flight time for particles born at different points along the beam. By suitably pulsing our microchannel plate detector, we can select particles born only where the laser beams overlap. This spatial gating in velocity map imaging can benefit nearly all photo-ion pump-probe VMI experiments especially when extreme-ultraviolet light or X-rays are involved which produce large background signals on their own.
关键词： signal-to-noise ratio,pump-probe experiments,X-rays,extreme-ultraviolet light,velocity map imaging,spatial gating
更新于2025-09-04 15:30:14