Angular distribution control of extreme ultraviolet radiation from laser-produced plasma by manipulating the nanostructure of low-density SnO 2 targets

金沢大学先端科学・社会共創推進機構We have found that the divergence of a relatively monochromatic extreme ultraviolet (EUV) emission from a laser-produced plasma can be manipulated by changing the target morphology which is a porous low-density tin oxide (Sn O2) structure. The fundamental light of a Nd-YAG laser was irradiated on the target with laser intensity of ∼ 1011 W cm2 and pulse duration of 10 ns. The nanostructure and density of the targets were tuned by a combination of colloidal polymer template and sol-gel processes [Gu, Nagai, Norimatsu, Fujioka, Nishimura, Nishihara, Miyanaga, and Izawa, Chem. Mater. 17, 1115 (2005)], which has a merit in large-scale preparation. When the target has an open cell nanostructure, the EUV emission directed predominantly along target normal, while a closed cell target exhibited divergent emission. The angular distribution may be affected by the orientation of the microstructured initial target, and this phenomenon can be applied to wavefront control of EUV emission. © 2006 American Institute of Physics.Embargo Period 12 month

Multilayerization of Organophotocatalyst Films that Efficiently Utilize Natural Sunlight in a One-Pass-Flow Water Purification System

A full-spectrum visible-light-responsive organophotocatalyst membrane array is designed and employed for a one-pass-flow water purification system. Whereas previous photocatalyst systems required strong light source, the present design manages with natural sunlight intensity, owing to multilayerization of a newly optimized low-absorbance organophotocatalyst. The design of the system is to utilize natural-sunlight-equivalent visible light with 1 m² of irradiation area to process 1 ton/day of water. A 1/3300 scale module of the system was constructed and experimentally demonstrated its viability. The reactor part of the flow system contains 24 stacked layers of organic-semiconductor-laminated Nafion film. The organic semiconductor is a bilayer of metal-free phthalocyanine (H₂<i>Pc</i>, p-type semiconductor) and 3,4,9,10-perylenetertacarboxylic-bisbenzimidazole (PTCBI, n-type semiconductor). Transparent Nafion functions as mechanical support and absorbent of trimethylamine, which was chosen as a typical contaminant of underground water in coastal areas. The reactor was irradiated for only 1 h/day by visible light (10 mW/cm²). The light intensity at the bottom layer was estimated to be 0.1 mW/cm², which was sufficient intensity (internal quantum efficiency was 0.15.) for the photocatalytic reaction, due to the optimized absorbance and photocatalytic quantum efficiency of each layer. The inlet TMA concentration was 3 ppm, while that of the outlet was less than 0.03 ppm for the first day of the operation of the system with and without the bilayer. Without the bilayer, the TMA concentration of the outlet flow increased after 20 days. With the bilayer, the TMA concentration of the outlet flow remained at less than 0.03 ppm for the 40-day experimental period due to its photocatalysis. The turnover number of photocatalytic reaction was calculated to be 1.8 × 10⁴

Spectroscopic study of debris mitigation with minimum-mass Sn laser plasma for extreme ultraviolet lithography

An experimental study was made of a target consisting of the minimum mass of pure tin (sSn) necessary for the highest conversion to extreme ultraviolet (sEUV) light while minimizing the generation of plasma debris. The minimum-mass target comprised a thin Sn layer coated on a plastic shell and was irradiated with a Nd:YAG laser pulse. The expansion behavior of neutral atoms and singly charged ions emanating from the Sn plasma were investigated by spatially resolved visible spectroscopy. A remarkable reduction of debris emission in the backward direction with respect to the incident laser beam was demonstrated with a decrease in the thickness of the Sn layer. The optimal thickness of the Sn layer for a laser pulse of 9 ns at 7×1010 W/cm2 was found to be 40 nm, at which low-debris emission in the backward direction and a high conversion to 13.5 nm EUV radiation were simultaneously attained