NewSUBARU Synchrotron Radiation Facility Research Articles

Photon energy dependence of graphene oxide reduction by soft X-ray irradiation and atomic hydrogen annealing

The effects of soft X-ray irradiation and atomic hydrogen annealing on the reduction of graphene oxide (GO) to obtain graphene were investigated. To clarify the interaction between soft X-rays and GO, soft X-rays of 300 eV and 550 eV were used for C 1s and O 1s inner-shell electron excitation, respectively at the NewSUBARU synchrotron radiation facility. Low-temperature reduction of the GO film was achieved by using soft X-ray at temperatures below 150 °C at 300 eV, and 60 °C at 550 eV. O-related peaks in X-ray photoelectron spectroscopy, such as the C–O–C peak, were smaller at 550 eV than those at 300 eV. This result indicates that excitation of the core–shell electrons of O enhances the reduction of GO. Soft X-rays preferentially break C–C and C–O bonds at 300 and 550 eV, respectively.

Experimental Demonstration to Control the Pulse Length of Coherent Undulator Radiation by Chirped Microbunching.

In seeded free electron lasers (FELs), the temporal profile of FEL pulses usually reflects that of the seed pulse, and, thus, shorter FEL pulses are available with shorter seed pulses. In an extreme condition, however, this correlation is violated; the FEL pulse is stretched by the so-called slippage effect in undulators, when the seed pulse is ultimately short, e.g., few-cycles long. In a previous Letter, we have proposed a scheme to suppress the slippage effect and reduce the pulse length of FELs ultimately down to a single-cycle duration, which is based on "chirped microbunching," or an electron density modulation with a varying modulation period. Toward realization of FELs based on the proposed scheme, experiments have been carried out to demonstrate its fundamental mechanism in the NewSUBARU synchrotron radiation facility, using an ultrashort seed pulse with the pulse length shorter than five cycles. Experimental results of spectral and cross-correlation measurements have been found to be in reasonable agreement with the theoretical predictions, which strongly suggests the successful demonstration of the proposed scheme.

Spatial profiles of collimated laser Compton-scattering γ-ray beams

The intensity and energy spatial distributions of collimated laser Compton scattering (LCS) γ-ray beams and of the associated bremsstrahlung beams have been investigated as functions of the electron beam energy, electron beam phase space distribution, laser optics conditions and laser polarization. We show that the beam halo is affected to different extents by variations in the above listed parameters. In the present work, we have used laser Compton scattering simulations performed with the eliLaBr code (https://github.com/dan-mihai-filipescu/eliLaBr) and real LCS and bremsstrahlung γ-ray beams produced at the NewSUBARU synchrotron radiation facility. A 500 μm MiniPIX X-ray camera was used as beamspot monitor in a wide γ-ray beam energy range between 1.73 MeV and 38.1 MeV.

Photoneutron cross section measurements on 208Pb

Photoneutron reactions on 208Pb in the Giant Dipole Resonance (GDR) energy range have been investigated at the γ-ray beam line of the NewSUBARU synchrotron radiation facility in Japan. Making use of quasi-monochromatic laser Compton scattering (LCS) γ-ray beams and of a novel flat-efficiency neutron detection system along with associated neutron-multiplicity sorting method, total and partial (γ,xn) photoneutron cross sections with x = 1 to 4 have been measured for 208Pb in a broad energy range covering the neutron threshold up to 38 MeV.

Photofission and photoneutron cross sections for 238U and 232Th

A specific objective of the recent IAEA Coordinated Research Project on Photonuclear Data and Photon Strength Functions (Code F41032; Duration 2016-2019) has been to measure photonuclear cross-section data where needed, for unexplored nuclei and cases of discrepant existing data. A dedicated experimental campaign has been conducted at the laser Compton-scattering γ-ray source of the NewSUBARU synchrotron radiation facility of SPring8, Japan, where photoneutron reactions for 11 nuclei from 9Be to 209Bi have been investigated in the Giant Dipole Resonance energy region. The measurements followed the development of a flat-effi ciency moderated neutron detection array and the associated neutron-multiplicity sorting techniques. The IAEA CRP campaign has been followed at NewSUBARU by new measurements of photofission and photoneutron reactions on 238U and 232Th in the energy range of 5.87 MeV – 20.14 MeV. The neutron-multiplicity sorting of high-multiplicity fission neutron coincidence events has been performed using a dedicated energy dependent, multiple firing statistical treatment. The photoneutron (γ, xn) and photofission (γ, fxn) reactions have been discriminated by considering a Gaussian distribution of prompt-fission-neutrons (PFN) multiplicities predicted by the evaporation theory. We here provide preliminary experimental (γ, n), (γ, 2n) and (γ, F) cross sections, average energies of PFN and of photoneutrons emitted in (γ, n) and (γ, 2n) reactions, as well as the mean number of PFN per fission act. The new 238U cross sections are compared with recent statistical-model calculations performed with the EMPIRE code on existing data.

Spectral distribution and flux of [formula omitted]-ray beams produced through Compton scattering of unsynchronized laser and electron beams

Intense, quasi-monochromatic, polarized γ-ray beams with high and tunable energy produced by Compton scattering of laser photons against relativistic electrons are used for fundamental studies and applications. Following a series of photoneutron cross section measurements in the Giant Dipole Resonance (GDR) energy region performed at the NewSUBARU synchrotron radiation facility, we have developed the eliLaBr Monte Carlo simulation code for characterization of the scattered γ-ray photon beams. The code is implemented using Geant4 and is available on the GitHub repository (https://github.com/dan-mihai-filipescu/eliLaBr). Here we report the validation of the eliLaBr code on NewSUBARU LCS γ-ray beam flux and spectral distribution data and two applications performed with it for asymmetric transverse emittance profiles electron beams, characteristic for synchrotrons.The first application is based on a systematic investigation of transverse collimator offsets relative to the laser and electron beam axis. We show that the maximum energy of the LCS γ-ray beam is altered by vertical collimator offsets, where the edge shifts towards lower energies with the increase in the offset.Secondly, using the eliLaBr code, we investigate the effect of the laser polarization plane orientation on the properties of the LCS γ-ray beams produced with asymmetric emittance electron beams. We show that:1. The use of vertically polarized lasers contributes to the preservation of the LCS γ-ray beam maximum energy edge by increasing the precision in the vertical collimator alignment.2. Under identical conditions for the electron and laser beams phase-space distributions, the energy spectrum of the scattered LCS γ-ray beam changes with the laser beam polarization plane orientation. More precisely, the use of vertically polarized laser beams slightly deteriorates the LCS γ-ray beam energy resolution.

An experiment demonstrating the capability of a symmetrical layout type double crystal monochromator controlled using electronic cam technology

A demonstration test of a newly developed double crystal monochromator was performed on beamline BL06 in the NewSUBARU synchrotron radiation facility of Hyogo University. Due to the symmetrical layout of the 1st crystal and 2nd crystal units of the monochromator, a maximum rotation speed of the main axis of up to 5.0 degrees/sec could be achieved. The monochromator is controlled by a newly developed control board programmed with an electronic cam algorithm. The control system allows the speed of both Z1 and Z2 axes to be successively synchronized as the Bragg angle changes. The Z 1 and Z 2 axes are moved apart by equal amounts from the center of gravity of the monochromator as the Bragg angle is increased. Also, the speed at which the Z1 and Z2 axes are moved apart increases with larger Bragg angle. This newly developed monochromator can maintain a stable exit beam height just as well as previous mechanical cam type monochromators proved on the height of the exit beam measured by an encoder system and observed by fluorescent screen. Due to the symmetrical layout and newly developed control system, the monochromator is suitable for industrial use because it can handle a wide energy range and allows high-throughput experiments to be carried out.

Monte Carlo simulation method of polarization effects in Laser Compton Scattering on relativistic electrons

Quasi-monochromatic, high energy and highly polarized γ-ray beam sources based on Compton scattering of laser photons (LCS) on relativistic electrons have developed for the last few decades as established instruments for nuclear physics studies. Following an extensive photoneutron experimental campaign at the LCS γ-ray beam line of the NewSUBARU synchrotron radiation facility at SPring8, Japan, a dedicated simulation code was developed for characterizing the incident γ-ray beams. The eliLaBr code is implemented using Geant4 and is available on the GitHub repository (github.com/dan-mihai-filipescu/eliLaBr). The present work describes step-by-step the Monte Carlo algorithm with focus on modeling the polarization properties of the scattered photon. The polarization is treated independently both in the Stokes parameters and in the polarization vector formalisms. An intervalidation between the two methods is given. Based on polarization state description requirements of different Geant4 physics classes, user recommendations are given on which of the two methods to be employed.The spatial and energy distributions for the LCS γ-ray beam and its Stokes parameters are obtained for head-on laser — relativistic electron collisions, where several incident laser polarization states were considered: linear, unpolarized, circular and mixed linear and circular polarization. Results of previous investigations on the polarization of Compton scattered photons are reproduced.The influence of variable incident angle between photon and electron beam was also investigated. We show that the degree of polarization transfer from the incident photon to the scattered photon increases with the collision angle, where head-on is considered 0°. However, as the polarization transfer is strongly influenced by the incident photon energy, we show that, for γ-ray sources based on Compton scattering of laser photons on relativistic electrons, the polarization degree of the incident photon is almost completely transferred to the scattered photon for any incident angle.

Effect of Cobalt Content on Charge Compensation Mechanism of LiNixMnyCozO2 Cathode for Lithium Ion Battery

LiCoO2 (LCO) is commonly used as a cathode for Li-ion batteries (LiBs) owing to its excellent intercalation nature, high voltage, and cyclic performance [1, 2]. However, LCO has issues due to the potential risk of future price increases of Co [3, 4]. Many efforts have been made to reduce the amount of Co in the cathode by replacing it with Ni and/or Mn, and LiNixMnyCozO2 (NMC) has been developed. NMC622, which contains 60 mol % of Ni in the transition metal composition, is now adopted in the majority of the electric vehicle battery chemistry. Although Ni-rich NMC is a promising alternative to low-Co cathodes, it is not clear whether the amount of Co can be further reduced from the present NMC622 without degrading cyclic stability. To further reduce the amount of Co, it is necessary to clarify the role of Co in the charge compensation mechanism and replace it with alternative elements with functions similar to those of Co.In this study, we conducted XAFS, XRD and first-principles calculations for the NMC cathode with various transition metal composition ratios to clarify that the roles of Co, Ni, Mn, and O in the charge compensation mechanism. Synchrotron X-ray experiments were performed at SPring-8 and NewSUBARU synchrotron radiation facility in Japan. The first-principles calculations were carried out with Vienna Ab-initio Simulation Package (VASP) [5, 6], which uses plane-wave basis sets.Fig. 1 shows the oxygen K-edge XANES spectra collected by the partial fluorescence yield (PFY) method at different states of charge (SOCs). As for the LCO, the peak intensity around 528 eV changed along with the SOC, suggesting that oxygen contributes to the charge compensation. Similar spectral changes were also observed with NMC111, NMC622, and slightly with NMC 811. In contrast, the white line energy in the Co L3-edge absorption hardly changed at any transition metal composition. Although there are various theories about the role of Co and oxygen in the charge compensation [7], our results show that there is no obvious change in the charge state of Co and oxygen contributes the most to the charge compensation in the LCO system. Detailed analysis including first-principles calculations will be discussed at the meeting.[1] K. Mizushima et al., Mater. Res. Bull. 15, 783 (1980).[2] A. Du Pasquier et al., J. Power Sources 115, 171 (2003).[3] P.A. Nelson et al., Modeling the Performance and Cost of Lithium-Ion Batteries for Electric-Drive Vehicles, Argonne National Laboratory, 2012.[4] Elsa A. Olivetti e t al., Joule 1, 229 (2017).[5] P. E. Blöch, Phys. Rev. B 50, 17953 (1994).[6] G. Kresse et al., Phys. Rev. B 59, 1758 (1999).[7] B. Li et al., Adv. Mater. 29, 1701054 (2017) Figure 1

Graphene synthesis from pentacene by soft X-ray irradiation

Although the formation of nanographenes such as graphene nanoribbons (GNRs) has been widely investigated, the formation methods are still severely limited by the lack of a suitable method for applying them. To address this, we investigated the use of soft X-rays to form GNRs. Precursor films were prepared by hot mesh deposition (HMD) using pentacene molecules and H2 gas. Various nanocarbon films, namely pentacene, 6,13-dihydropentacene, and a mixture of pentacene, 6,13-dihydropentacene, and pentacene oligomers were prepared by HMD then irradiated using soft X-rays generated in the NewSUBARU synchrotron radiation facility. The properties of the nanocarbon films synthesized from pentacene, 6,13-dihydropentacene, and pentacene oligomers by soft X-ray irradiation differed. The hydrogen desorption and catalytic effect of the Ni film on the quartz substrate during soft X-ray irradiation enhanced the polymerization of pentacene. The pentacene oligomers acted as nuclei for graphene formation. Although GNRs were not synthesized by soft X-ray irradiation, graphene was obtained with a high yield at a low temperature of 760 °C.

New 209Bi photodisintegration data and physical criteria of data reliability

The well-known problem of noticeable disagreements between photoneutron cross sections from various experiments was discussed in detail for 209Bi. Data for partial photoneutron reactions cross sections obtained at Livermore (USA) using quasimonoenergetic annihilation photons and the method of neutron multiplicity sorting were analyzed using the objective physical criteria and the experimental-theoretical method for evaluation. Because of significant systematic uncertainties involved in the method for determining the neutron multiplicity, experimental data do not satisfy the criteria of reliability and differ noticeably from the evaluated data. The new experimental data for 209Bi (γ, in) reactions with i = 1–4 were obtained using quasimonochromatic laser Compton-scattering (LCS) γ-ray beams at the NewSUBARU synchrotron radiation facility and the novel technique of direct neutron-multiplicity sorting with a flat-efficiency detector. It was found that new σ(γ, 1n), σ (γ, 2n), and σ (γ, 3n) contradict noticeably to the Livermore data. It was shown that at the same time the new 209Bi photoneutron cross-sections are in good agreement with data evaluated using experimental-theoretical method and assuring the reliability of those.

γ -ray strength function for barium isotopes

Photoneutron cross sections were measured for $^{137}\mathrm{Ba}$ and $^{138}\mathrm{Ba}$ at energies below two-neutron threshold using quasimonochromatic $\ensuremath{\gamma}$-ray beams produced in laser Compton scattering at the NewSUBARU synchrotron radiation facility. The photoneutron data are used to constrain the $\ensuremath{\gamma}$-ray strength function on the basis of the Hartree-Fock-Bogolyubov plus quasiparticle random phase approximation using the Gogny $D1M$ interaction. Supplementing the experimentally constrained $\ensuremath{\gamma}$-ray strength function with the zero-limit $E1$ and $M1$ contributions, which are unique to the deexcitation mode, we discuss radiative neutron capture cross sections relevant to the $s$-process nucleosynthesis of barium isotopes in the vicinity of the neutron magic number 82.

γ -ray strength function for thallium isotopes relevant to the Pb205−Tl205 chronometry

Photoneutron cross sections were measured for $^{203}$Tl and $^{205}$Tl at energies between the one- and two-neutron thresholds using quasi-monochromatic $\gamma$-ray beams produced in laser Compton-scattering at the NewSUBARU synchrotron radiation facility. Our new measurement results in cross sections significantly different from the previously reported bremsstrahlung experiment, leading to rather different GDR parameters, in particular to lower GDR peak energies and higher peak cross sections. The photoneutron data are used to constrain the $\gamma$-ray strength function on the basis of the Hartree-Fock-Bogolyubov plus quasi-particle random phase approximation using the Gogny D1M interaction. Supplementing the experimentally constrained $\gamma$-ray strength function with the zero-limit E1 and M1 contributions for the de-excitation mode, we estimate the Maxwellian-averaged cross section for the s-process branching-point nucleus $^{204}$Tl in the context of the $^{205}$Pb - $^{205}$Tl chronometry.

Deep X-ray lithography system with a uniform and high-accuracy fabrication area established in beamline BL11 at NewSUBARU.

A new lithography system to fabricate high-aspect-ratio 3D microstructures was developed at the NewSUBARU synchrotron radiation facility (University of Hyogo, Japan). The X-ray beam generated by this system has high parallelism (horizontal and vertical divergence angles of 278 µrad and 14 µrad, respectively) and high photon flux (31 mW mm-2 at a beam current of 300 mA). The high photon flux and exposure area of the system were validated and a beam-scan method for a large exposure area with a uniform dose distribution has been proposed. In addition, the deep X-ray lithography performance was characterized using a conventional photosensitive material and the synchrotron-radiation-induced direct etching of polytetrafluoroethylene (PTFE) was demonstrated. An enlargement of the microfabrication area up to 100 mm × 100 mm while contemporarily ensuring high uniformity was achieved.

Photoneutron cross sections for Ni isotopes: Toward understanding (n,γ) cross sections relevant to weak s -process nucleosynthesis

Photoneutron cross sections were measured for $^{58}$Ni, $^{60}$Ni, $^{61}$Ni, and $^{64}$Ni at energies between the one-neutron and two-neutron thresholds using quasi-monochromatic $\gamma$-ray beams produced in laser Compton-scattering at the NewSUBARU synchrotron radiation facility. The new photoneutron data are used to extract the $\gamma$-ray strength function above the neutron threshold complementing the information obtained by the Oslo method below the threshold. We discuss radiative neutron capture cross sections and the Maxwellian-averaged cross sections for Ni isotopes including $^{63}$Ni, a branching point nucleus along the weak s-process path. The cross sections are calculated with the experimentally constrained $\gamma$-ray strength functions from the Hartree-Fock-Bogolyubov plus quasi-particle-random phase approximation based on the Gogny D1M interaction for both $E1$ and $M1$ components and supplemented with the $M1$ upbend.

(Invited) Engineering of Nickel Oxide Hole Transport Layer for Inverted Perovskite Solar Cells

Introduction The NiOx layer is actively used as hole extraction layer for inverted structure perovskite solar cells. However, clear guidelines on NiOx chemical composition, manufacturing methods, energy levels, and the hole-transport process remain unclear. In this conference, high-density NiOx layers with various manufacturing temperatures are produced with Nickel acetylacetonate using the SPD method in order to improve the performances of inverted perovskite solar cells. The chemical composition of the NiOx is investigated using XPS, and GIXRD. Furthermore, the influence of Na+ ions in the valence band of the NiOx layer is investigated by vacuum ultraviolet photoelectron spectroscopy using synchrotron radiation. The results showed that the conversion efficiency of the perovskite solar cell is high as the crystallite size of NiOx is large. The highest perovskite solar cell conversion efficiency was obtained at a NiOx layer production temperature of 550 °C. Inverted perovskite solar cells were fabricated with over 16.1% conversion efficiency. Conversion efficiency of solar cell The conversion efficiencies of the perovskite solar cells using NiOx films with various deposition temperatures are summarized in Table 1. The perovskite solar cells conversion efficiency increased along with the NiOx layer production temperature to 550 and 600 °C; however, it decreased slightly when the temperature increased further to 600 °C. As a result, the perovskite solar cell conversion efficiency reached its peak when the NiOx layer production temperature was 500 °C. To highlight the performance change, we herein investigated the composition, structure and the band state of the NiOx layers. Influence of valence band and valence of Ni ion of the NiOx layers To investigate the states of the regions near the edges of the valence bands of the NiOx layers, PES measurements were carried out with a BL-07B at the NewSUBARU synchrotron radiation facility, and the results are shown in Figure 1. The regions near the edges of the valence bands of the NiOx correspond to Ni 3d (label A), O 2p (label B), and the charge transfer transition from an O 2p level to Ni 3d photoionization (label C). From the PES measurement results, the region (around 4-5 eV) corresponding to O 2p was stronger at 300 and 600 °C than at 500 °C. This is because the influence of the O 2p orbital increased because the proportion of oxygen in NiOx increased owing to the loss of Ni ions. Although the ratio of Ni2+ to Ni3+ ions affects the energy levels in the vicinity of the HOMO, a change in these energy levels does not contribute to hole extraction in perovskite solar cells. From these results, it was found that the valence of the Ni ions has little influence on the performance of the solar cells. Crystal analysis of the NiOx layers Both the structures and crystallite sizes of the thin NiOx films formed by SPD were investigated via GIXRD, as shown in Figure 2. The five peaks that appeared at 2θ values of approximately 37.6° 43.6°, 63.3°, 75.6°, and 79.6° were assigned to the 111, 200, 220, 311, and 222 planes, respectively, and then attributed to the randomly oriented NiOx crystal. At 250 °C, no diffraction peaks were observed because the NiOx film did not crystallise. This implies that crystallised NiOx films formed with annealing temperatures above 300 °C. The NiOx crystallite sizes were calculated from the intensities of the 200 peaks using the Scherrer equation, and the results are shown in Figure 1, which indicates that their sizes increased with increasing SPD temperatures. The size of a NiOx crystallite and the tendency of conversion efficiency were consistent, except at 550 and 600 °C, where the FTO layer broke beyond the glass transition point. In other words, as a guideline for manufacturing high-performance inverted perovskite solar cells, it is important to enlarge the crystallites in the NiOx film. Conclusions We demonstrated that it is related to the NiOx crystallite size and the conversion efficiency of the perovskite solar cells, which can be used as a guideline to achieve high performance. The highest perovskite solar cell conversion efficiency was obtained at a NiOx layer production temperature of 500 °C. In the inverse perovskite solar cell, the conversion efficiency exceeded 16.1%, and hysteresis was not observed. Moreover, the measurements of the valence band using synchrotron radiation indicated that the ratio of Ni2+ to Ni+3 had little effect on the solar cell performance. This is an important guideline for improving the performance of perovskite solar cells. Acknowledgement This work was supported by New energy and industrial Technology Development Organization (NEDO), Japan.

Large take-off angle dependence of C-K emission spectra observed in highly oriented pyrolytic graphite

We have constructed a compact soft X-ray emission spectrometer at the BL-09A beamline of the NewSUBARU synchrotron radiation facility at the University of Hyogo, Japan. Using this spectrometer, we observed a large take-off angle dependence of C-K emissions in highly oriented pyrolytic graphite (HOPG). At an excitation photon energy of 310eV, far from the absorption edge of HOPG, we detected large take-off angle dependence of π→1s emission. The π emission intensity was much higher than that of σ emission, which has not been reported before. One reason for the apparent discrepancy between these results and previous ones probably originates from the difference in energy resolving power of the emission spectrometers used. According to a band calculation for HOPG, the large angle dependence observed here could be attributed to the resonant transition of 1s electrons to a π state 25eV higher than the Fermi level.

Photoneutron Reactions in Nuclear Astrophysics

Highly-monochromatic γ-ray beams are produced at the NewSUBARU synchrotron radiation facility by the inverse Compton scattering of laser photons from relativistic electrons. The latest s-process study in nuclear astrophysics with the γ-ray beam is presented.

In-situ Contamination Thickness Measurement by Novel Resist Evaluation System at NewSUBARU

To reduce the influence of carbon contamination growth, which is the origin of the resist outgassing during extreme ultraviolet (EUV) exposure, it is necessary to study the relationship between the outgassing species from the resist and carbon contamination growth during EUV exposure. Thus a novel evaluation system which enable the measurement of the carbon contamination thickness on a Mo/Si multilayer witness sample by in-situ ellipsometry in the resist outgassing environment under EUV exposure was installed at the beamline in the NewSUBARU synchrotron radiation facility. The carbon contamination thickness on the witness sample measured by in-situ ellipsometry is in good agreement with those measured using an atomic microscope and by reflectivity measurement. In addition, it is found that the time dependence of the carbon growth on a witness sample is due to the difference in outgassing species from the resist samples during EUV exposure. Furthermore, for the model resist of poly(hydroxystyrene) containing the protectiive group of tertial butoxycarbonyl group with a photoacid generator (PAG) and a quencher, the time dependence of contamination thickness was mainly due to the decomposition of outgassing species of the tert-butoxycarbonyl group and the residual casting solvent, such as propyleneglycol monomethyl ether acetate. In order to evaluate the carbon contamination thickness measurement, the in-situ measurement system was moved to the 10.8-m-long undulator beamline. The EUV light intensity flux was estimated to be the same level as that required in high-volume manufacturing.

Critical Dimension Measurement of an Extreme-Ultraviolet Mask Utilizing Coherent Extreme-Ultraviolet Scatterometry Microscope at NewSUBARU

We have developed a coherent extreme ultraviolet scatterometry microscope (CSM) for actinic inspection and metrology of an extreme ultraviolet (EUV) mask. It was installed at the BL-3 beamline of the NewSUBARU synchrotron radiation facility. The CSM is a lens-less system with no objective, and aerial images and critical dimension (CD) values are estimated using the recorded diffraction image. A method of measuring CD values by reconstruction of aerial images using diffraction intensity has been developed. A repeatability of 0.3 nm (3σ) with a high precision is achieved with the actinic method. We also evaluate the CD uniformity of the 88 nm lines-and-spaces patterns on the finished EUV mask, which corresponds well with that obtained by critical-dimension scanning electron microscopy (CD-SEM) results.