Minaji Furudate

Ellipsometry in the extreme ultraviolet region with multilayer polarizers

Abstract The sensitivity of ellipsometry to bulk surfaces and thin films in the extreme ultraviolet region is studied theoretically in reference to the complex refractive indices of the materials and the extinction ratio of a multilayer polarizer. At a photon energy of 97 eV, which is 12.8 nm in wavelength, sensitivities in terms of the minimum detectable differences to a refractive index of 0.027 and to an extinction coefficient of 0.048 can be expected for bulk surfaces. For a thin film sample, the sensitivities are 10 −3 nm for the thickness, 10 −4 for the refractive index and 10 −5 for the extinction coefficient. Ellipsometry in this wavelength region proves to be useful for the study of the near-surface region of the sample within a penetration depth of approximately 150 nm with good material and optical structure sensitivity.

Soft x‐ray emission spectrometer equipped with a multilayer rotating analyzer for study of the polarized emission

A soft x‐ray emission spectrometer equipped with a multilayer rotating analyzer has been made. The spectrometer covers an energy range of 50–500 eV with a resolution power of about 300. Using the rotating analyzer we have measured the polarization of the B K emission of h‐BN, and have found that it is dominantly polarized perpendicularly to the c‐axis, which agrees well with the experimental result.

Polarization performance of EUV transmission multilayers as λ/4 and λ/2 plates at a photon energy of 97 eV

Abstract Complex relative amplitude transmittance ρ = T p /T s of extreme ultraviolet transmission multilayers fabricated to three numbers of layers has been evaluated by ellipsometry with synchrotron radiation at a photon energy of 97 eV. Large phase shifts enough to be a quarter-wave plate and a half-wave plate have been observed with respective transmittances of 10 and 0.5%.

Compact debris shutter design of a laser-produced plasma source for high-NA application

A compact debris shutter for use with a laser produced plasma source is designed for installation to our EUV interferometer. The shutter is for operation under vacuum based on a gyroscope design for space satellites. It is of a hollow cylinder shape of 20 cm diameter enabling to stop debris of the plasma source traveling at a speed below 260 m/s at a spinning speed of 6000 rpm.

DESIGN AND FABRICATION OF MULTILAYER MIRRORS FOR He-II RADIATION

Design, fabrication, and reflectance evaluation of multilayer mirrors for He-II radiation are described. Based on the available complex refractive indices of materials at the wavelength of 30.4 nm, Mg, Al, Si, Cr, and C were selected as small absorption material to be paired. Mo/Si and Sc found in previous works were also included. In referring to optimum design for the highest reflectance, multilayers of Al/Mg, Au/Mg, C/Mg, Sc/Mg, C/Si, Al/C, and Mo/Si were fabricated by ion-beam sputtering. The highest reflectance of 27% was observed by a 15-period Mg/Sc mirror.

Polarization study on the B 1s exciton emissions from h-BN and B2O3

We have measured the polarization degree of the B 1s exciton emission from h-BN and B2O3 under resonance excitation using a multilayer rotating analyzer. The emission would include the luminescence due to the direct recombination of the core exciton and the elastic (Rayleigh) scattering components. We have observed a definite contribution of the recombination luminescence to the exciton emission.

First thin film ellipsometry at a photon energy of 97eV with use of high-performance multilayer polarizers

In the extreme ultraviolet (EUV) region, synthetic multilayer structures are found useful as reflection polarizers. Such structures of transmission type made by removing from substrates are found useful as polarizers and phase shifters. With these multilayer polarizing elements developed, the first thin ellipsometry was performed at a photon energy of 97 eV (12.8 nm in wavelength), which demonstrated atomic sensitivity of the EUV ellipsometry.

A simple accurate method of alignment of beamline optics with the use of EUV multilayer polarizers

A simple alignment method is proposed, which enables the alignment of beamline optics of a bending section accurately, relying on the linear state of polarization of synchrotron orbital radiation rather than the beam intensity. The method utilizes extreme UV (EUV) multilayers as a compact polarization monitor detecting unwanted vertical polarization components. The proposed method was found to be far more sensitive than that relying on the maximum intensity. Another advantage is the insensitivity to surface contamination, such as an irradiation mark on the mirror degrading reflectance. A design example is presented for use around a photon energy of 370 eV along with an experimental example at a photon energy of 97 eV.

Polarization studies on the B 1s exciton emission from h-BN using a soft x-ray multilayer polarizer

We have measured the polarization degree of the B 1s exciton emission from h-BN under resonance excitation using a multilayer rotating analyzer. We used a Mo/C 101 layers in total as a soft x-ray polarizer. The emission would include the luminescence component due to the direct recombination of the core exciton and the elastic (Rayleigh) scattering of the incident light. We have found a definite contribution of the recombination luminescence to the exciton emission peak.