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

Cheiron School
September 25, 2014
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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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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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 donot, 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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CXRO Web Site

X-Ray Interactions with Matter . Search CXRO

Facilities
Publications
ResearchX-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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Focusing with curved glancing incidence optics

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Fluorescent microprobe based in crossed
cylinders

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High resolution x-ray diffraction under high pressure using
multilayer coated focusing optics

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X-ray microprobe at SPring-8
Optical microscope	f1: 25298m	

mm	

PIN photodiode	mm	
f2: 15045m	

Undulator	

DCM	
TC1Slit	

Mirror manipulator	
Ion chamber	Incident Slit	

SDD	Beam monitor	
Sample & Scanner	

Experimental hutch	

2006

Front end	

Courtesy of K. Yamauchi andH. Mimura, Osaka University.
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Normal incidence reflection at an interface

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Diffractive optics for soft x-rays and EUV

Zone Plates

Gratings

PinholesCheironSchool_Sept2014_Lec1.ppt

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Diffraction from a transmission grating

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A Fresnel zone plate lensCheironSchool_Sept2014_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 lensfor soft x-ray microscopy

Courtesy of E. Anderson, LBNL
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Zone plates for ALS STXM beamlines –“3D Engineered Nanostructures”
Δr = 35 nm, Δt = 180 nm Au, N = 1700
D = 240 µm, 3 x 95 µmD central stop

Inner zones

Outerzone
close-upOuter zones

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The Nanowriter: high resolution electron beam
writing with high placement accuracy

Courtesy of E. Anderson (LBNL)
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New x-ray lenses: Improving contrast and resolution
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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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 diffractslight and is just capturedby the lens – setting
the diffraction limited
resolution limit.

Diffraction from an
object 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)
32(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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New	  ultra	  high	  aspect	  ra0o,	  high	  eﬃciency,	  hard	  x-­‐ray	  zone	  plates	  for	  high	  spa0al	  resolu0on	  at	  30-­‐50	  keV	  Δr = 100 nm
Δh = 6.6 µm

3.4 µCourtesy of Anne Sakdinawat and Chieh Chang (SLAC)

Specialized	  x-­‐ray	  diﬀrac0ve	  op0cal	  elements	  enable	  new	  science	  at	  synchrotron	  facili0es	  Spiral zone plate for
producing x-rays withcharge 50 orbital
angular momentum

Uniformly redundant
array for x-ray parallel
holography, alignment,
and other applications

Zone plate for x-ray
differential
interference contrast
microscopy

Courtesy of Anne Sakdinawat and Chieh Chang (SLAC)A high quality Mo/Si multilayer mirror
N = 40d = 6.7

Courtesy of Sasa
ˇ Bajt (LLNL)

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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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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 sample

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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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MAESTRO: A new varied-line-space grating monochromator beam linefor angle-resolved-photo-electron-spectroscopy with high spectral andspatial resolution at the Advanced Light Source
Jason Wells, Derek Yegian, Ken Chow, Eli Rotenberg, Aaron Bostwick, Geoff Gaines and Tony Warwick

The latest soft x-ray undulator spectroscopy beam line planned for the ALS serves MAESTRO a new highresolution Angle Resolved Photo Emission facility with zone-plate focused nano-ARPES. The beam line
design offers spectral resolution 1:30000 from 60eV to 400eV with an extended energy range from 20eV to1000eV. Challenges include optical figure quality, thermal engineering, source size and stability and vibrationsin the monochromator. The optical design is radical in that a VLS grating will provide all of the focusing in thedispersion direction, and the mirrors are plane, except for a sphere to collect and focus horizontally.
Courtesy of Eli Rotenberg and Tony Warwick (ALS)

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Varied line space gratingsVaried-Line-Space Plane Gratings provide focusing and aberration correction along with the dispersion
that they generate in the monochromator. They can be used to erect the monochromator focal plane,making the position of the focus at the exit slit (almost) stationary as the grating rotates to select thephoton energy. Beyond that, they are now being used to replace the focusing from shaped optics, making
beam lines cheaper and easier to align.	

The PEEM3 beam line at 11.0.2 uses aTriple-Ruled Varied-Line-Space grating:Linear and non-linear
line density variation1) to erect the focal plane on a
stationary set of exit slits2) to keep the zero-order light infocus, for easy tuning, and formonitoring of the photon energy.

AFMmeasuredgroove shapes

Courtesy of Tony Warwick (ALS)

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MAESTRO: A new varied-line-space grating
monochromator beam line at the ALS

9.25m
MaestroEPU

M201

Shield wall

7.25m (to grating)
Switch-M202

2.00m yard

G201a
G201b
Monochromator
G202a
G202b

2.50m
0.50m
0.80m
M214
Exit M212 M213
KB focusing microARPES
slitmirrors

M211
M221Exitslit~2.75m

Zone plate

Courtesy of Tony Warwick (ALS)nanoARPES

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MAESTRO at the ALS: gratings and efficiencies

Courtesy of Tony Warwick (ALS)

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Water-cooled optics are essential: correcting
slope errors due to a thermal bump

Heighterror
Body plate showing pockets
for cooling channels

Tangential
slope error

Sagittalslope error

Courtesy of Tony Warwick (ALS)

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Ray tracing beamlines is an important tool
Significant degradation of the spectral resolution occurs due to localized heating of M202. It isalmost entirely corrected by adjusting the monochromator focusing parameter from 3.93 to4.02. The engineering design will allow this mirror to be built with 1mm thick hot-wall and theactual thermal deformation is expected to be less.

600lines_60eV_10000_c=3.93034_18.7_0.038_
1.5mmheatbump

600lines_60eV_10000_c=4.02_18.7_0.038_
1.5mmheatbumpcorrected

Courtesy of Tony Warwick (ALS)

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Typical parameters for synchrotron radiation

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Time structure of synchrotron radiation

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Photon energy, wavelength, power

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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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