No abstract

One of fundamental aims of extreme ultraviolet (EUV) lithography is to maximize brightness or conversion efficiency of laser energy to radiation at specific wavelengths from laser produced plasmas (LPPs) of specific elements for matching to available multilayer optical systems. Tin LPPs have been chosen for operation at a wavelength of 13.5 nm. For an investigation of EUV radiation of laser-produced tin plasmas, it is crucial to study the related atomic processes and their evolution so as to reliably predict the optimum plasma and experimental conditions. Here, we present a simplified radiation hydrodynamic model based on the fluid dynamic equations and the radiative transfer equation to rapidly investigate the evolution of radiation properties and dynamics in laser-produced tin plasmas. The self-absorption features of EUV spectra measured at an angle of 45° to the direction of plasma expansion have been successfully simulated and explained, and the evolution of some parameters, such as the plasma temperature, ion distribution and density, expansion size and velocity, have also been evaluated. Our results should be useful for further understanding of current research on extreme ultraviolet and soft X-ray source development for applications such as lithography, metrology and biological imaging.

Large-area horizontal-aligned ZnO nanotubes (ZNTs), TiO2 nanotubes (TNTs), TiO2–ZnO core–shell nanotubes (TZNTs) and ZnO-TiO2 core–shell nanotubes (ZTNTs) were successfully synthesized by electrospinning combined with pulsed-laser deposition. The morphology, structure, and composition of the samples were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, and Raman spectroscopy. The photoluminescence (PL) spectra of these samples indicate that the addition of a TiO2 layer greatly decreases the recombination of photogenerated carriers in the heterojunction nanotubes. The photodetectors (PDs) were fabricated by assembling horizontally ordered nanotubes on the gold interdigital electrode, and their ultraviolet (UV) detection performances were compared. The test results at room temperature show that the PD with aligned ZTNTs have the best UV response and a short response recovery time. In addition, the performance of ZTNT PDs and TZNT PDs are further improved under heating. The photo/dark current ratio, responsivity (R λ), detectivity (D*), and external quantum efficiency (EQE) of ZTNTs increased to 388, 450 uA·W–1, 1.1 × 1010 cm·Hz1/2·W–1, and 0.15%, respectively, under the condition of 365 nm UV radiation with a power density of 4.9 mW·cm–2 and a 1 V bias at 90 °C. The UV response mechanism and structural superiority of the horizontally ordered coaxial heteronanotube were also discussed. In addition, this work provides an important method for the design of other ordered nanomaterials and structures, which have a wide range of applications in the fields of sensors, transistors, transparent flexible electrodes, and other multifunctional devices.

We measured time-resolved spectra of laser-produced plasma of Si in a vacuum at the early phase evolution (30–100 ns) and found clear signs of spectral line broadening. Based on the measured line intensities of Si2+ and Si3+ ions, the Saha–Boltzmann method is used to diagnose the electron temperature. The Stark broadening of different high-charge ion lines is combined with a modified Griem semi-empirical formula to diagnose the electron density of Si plasma in the early evolutionary stage. The effects of self-absorption, natural broadening, and Doppler broadening on the spectral profiles were evaluated. We also conducted experiments to verify that current experimental conditions satisfied the local thermodynamic equilibrium conditions. Finally, time evolutions for the electron temperature and electron density in the early stage of plasma evolution were obtained.

The temporal evolution of extreme ultraviolet emission from a laser-produced aluminum plasma has been experimentally and theoretically investigated. Spectra of highly charged Al ions have been measured by using the temporal-spatially resolved laser-produced plasma emission technique. In order to deeply understand the evolution of plasmas and achieve the purpose of rapid diagnosis, a collisional-radiative model has been resolved in the steady-state and time-dependent cases, respectively. The evolution of rate coefficients as a function of the electron temperature, electron density, and time delay has been discussed, respectively. In addition, the influence of the photo-ionization process has also been evaluated for the ionization balance. The results indicate that the time evolution analysis of spectra is useful for the accurate understanding of the evolution behavior of highly charged ions in laser-produced plasmas.