EUV, Soft and Hard X-Ray
Optics and Beamlines
David Attwood
University of California, Berkeley

Cheiron School
September 2015
SPring-8
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The short wavelength region of the electromagneticspectrum

n = 1 – δ + iβ

δ, β << 1
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Available x-ray optical techniques

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Beamlines are used to transport photons to the sample, andtake a desired spectral slice

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A typical beamline: monochromator plus focusing optics todeliver radiation to the sampleCheironSchool_Sept2015_Lec1.ppt

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High spectral resolution (meV beamline)

Courtesy of Zahid Hussein (ALS)
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Beamline 7.0 at Berkeley’s
Advanced Light Source

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Basic ionization and emission processes
in isolated atoms

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Energy levels, absorption edges, and characteristic line
emissions for a multi-electron atom

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Energy levels, quantum numbers, andallowed transitions for the copper atom

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Refractive index from theIR to x-ray spectral region

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Refractive index at nanometer wavelengths

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Refractive index in the soft x-ray
and EUV spectral region

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Photoionization and electron binding energies

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Normal incidence reflection at an interface

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Hard x-ray imaging based on glancing incidence
reflective optics• Optics behave differently at these very short wavelengths(nanometers rather than 520 nm green light)• The refractive index is less than unity, n = 1 – δ + iβ
• Waves bend away form the normal at an interface• Absorption is significant in all materials and at all wavelength.
• Because of absorption, refractive lenses do not work, prisms do
not, windows need to be extremely thin (100 nm or less).
• Because light is bent away from the surface normal, it possible tohave “total external reflection” at glancing incidence – a commonlyused technique.
• Kirkpatrick-Baez (KB)
mirror pair

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Glancing incidence optics

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Total external reflection with finite β

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X-ray mirrors at Glancing incidence

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Elliptical x-ray mirrors

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Focusing with curved glancing incidence optics

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Glancing incidence mirrors for Astrophysics: the“spiral galaxy”
30 M light years

Courtesy	  of	  	  Harvard-­‐Smithsonian	  Center	  for	  Astrophysics	  CheironSchool_Sept2015_Lec1.ppt

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Fluorescent microprobe based in crossedcylinders

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Hard x-ray nanoprobe at SPring-8

Courtesy of H. Matsuyama andK. Yamauchi, Osaka University.
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Spring-8 hard x-ray nanoprobe to 7 nm spot size

Courtesy of H. Mimura andK. Yamauchi, Osaka University.
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Diffractive optics for soft x-rays and EUV

Zone Plates

Gratings

PinholesCheironSchool_Sept2015_Lec1.ppt

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Diffraction from a transmission grating

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A Fresnel zone plate lensCheironSchool_Sept2015_Lec1.ppt

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A Fresnel zone plate lens used as a diffractive lens forpoint to point imaging

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Depth of focus and spectral bandwidth

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A	  Fresnel	  zone	  plate	  lens	  for	  so/	  x-­‐ray	  microscopy	  Courtesy of Anne Sakdinawat, SLAC/Stanford; C. Chang and A. Sakdinawat, Nature Communications (27Jun2014).

Dual functionality x-ray lenses: Improving contrast andresolution for x-ray microscopy

C. Chang, A. Sakdinawat, P.J. Fischer, E.H. Anderson, D.T. Attwood, Opt. Lett. 2006; Sakdinawat and Liu, Opt. Lett. 2007;
Sakdinawat and Liu, Opt. Express 2008
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New	  ultra	  high	  aspect	  ra;o,	  high	  eﬃciency,	  hard	  x-­‐ray	  zone	  plates	  for	  high	  spa;al	  resolu;on	  at	  30-­‐50	  keV	  Δr = 100 nm
Δh = 6.6 µm

3.4 µCourtesy of Anne Sakdinawat, SLAC/Stanford; C. Chang and A. Sakdinawat, Nature Communications (27Jun2014).

Diffraction limited x-ray imaging
For example, the widely accepted Rayleigh criteria for resolving twoadjacent, mutually incoherent, point sources of light, results in a 26%
intensity modulation.
λ = 2.48 nm(500 eV)Two overlapping
Airy patterns

Δrresol. = 0.61 λ / NA

Note: Other definitions arepossible, depending on theapplication and the ability todiscern separated objects.

Resultant intensity pattern when
the two point sources are “justresolved”, such that the central
lobe maximum due to one point
source overlaps the firstminimum (dark ring) of the other.
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Resolution and illumination
Achievable resolution can be improved by varying illumination:
An object pattern ofperiodicity d diffracts
light and is just capturedby the lens – setting
the diffraction limited
resolution limit.

Diffraction from anobject of smaller
periodicity, d/2, is justcaptured, and resolved,
when illuminatedfrom an angle.

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Resolution, illumination, and optical transfer function

Spatial frequency response of the optical system can be optimized by tailoring
the angular distribution of illumination.

σ=NAcond
NAobj(10.3)

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λ = 1.52 nm (815 eV)
Δr = 15 nm
N = 500
D = 30 µm
f = 300 µm
σ = 0.38
0.8 Δr = 12 nm

Cr/Si test pattern (Cr L3 @ 574 eV)
4 ph/pixel)
37(2000 X 2000, 10
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Hard x-ray zone plate microscopy• Shorter wavelengths, potentially better spatial
resolution and greater depth-of-field.
• Less absorption (β); phase shift (δ) dominates,
higher efficiency.
• Thicker structures required (e.g., zones), higher
aspect ratios pose nanofabrication challenges.
• Contrast of nanoscale samples minimal; will require
good statistics, uniform background, dose mitigation.

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A high quality Mo/Si multilayer mirror
N = 40d = 6.7

Courtesy of Sasa
ˇ Bajt (LLNL, now DESY)

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Scattering by density variations within a multilayer
coating

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Multilayer mirrors satisfy the Bragg condition

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High reflectivity, thermally and environmentally robust multilayer
coatings for high throughput EUV lithography

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Atomic scattering factors for silicon (Z = 14)

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Atomic scattering factors for molybdenum (Z = 42)

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Sputtered deposition of a multilayer coating

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Time structure of synchrotron radiation

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Typical parameters for synchrotron radiation

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Photon energy, wavelength, power

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CXRO Web Site

X-Ray Interactions with Matter . Search CXRO

Facilities
PublicationsResearchX-Ray Tools
Visitors
Personnel
Comments?
Server Stats. About CXRO

www.cxro.LBL.gov/• Atomic scattering factors• EUV/x-ray properties of the elements• Index of refraction for compound materials• Absorption, attenuation lengths, transmission• EUV/x-ray reflectivity(mirrors, thin films, multilayers)• Transmission grating efficiencies• Multilayer mirror achievements• Other
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2nd Edition in progress: new FEL, HHG, Coherence,and X-ray Imaging chapters

UC Berkeley
www.coe.AST.berkeley.edu/sxr2009
www.coe.AST.berkeley.edu/srms
www.youtube.com

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