multilayer mirrors for x-rays - linköping university · "highlights in physics" 2005 by...

"Highlights in Physics" 2005 by Jens Birch <[email protected]> 1

Multilayer mirrors for X-Rays

Jens Birch and Naureen Ghafoor

Thin Film Physics

Department of Physics, Chemistry, and Biology (IFM) 450 pers

Biologi Kemi

Materialfysik ca 120 personer

Teori och modellering Tillämpad fysik


Applications of Multilayer X-ray Mirrors

• X-ray lithography -micro electronics (EUV)

• X-ray telescopy -solar observations-deep space telescopy

•X-ray spectroscopy -flourescence-cosmology

• X-ray FEL -femto second chemistry and physics

• X-ray microscopy -proteins, DNA,...

What is light?

Light is rays…

But also waves

wavelength


Visible lightwaves

Violet Red

wavelength(nm)

Inte

nsit

y

Short wavelength long wavelength

Sensitivity of the eye

Light waves are ”bent” in a small hole

Water waves are ’bent’when passing piers.

photographicfilm

Short waves are diffracted less than long

Use as short wavelength as possible for highest resolution!

DIFFRACTION!

hole in board


More lightwaves

våglängd (m)

X-rays are diffracted less than visible light!

Long wave radiowavelength: ca 10 km

(10 000 m)

FM radioTV

Idea: Use x-rays for a microscope!

X-rayswavelength: 0,05 - 5 nm

(ca 0,000000001 m)

X-rays

• large absorption in proteins

Photon wavelength (nm)

C K-edgeO K-edge

Use the water window for microscopy: • <50 nm resolution• biologic specimens

• small absorption in water

the ”Water window”

• λ = [2.4 - 4.4 nm] (soft x-raysthe ”water window”

Absorption of electro-magnetic radiation


Refraction

Different wavelengths are refracted by different amountssince they have different velocities

X-rays travel almost with the same speedand are therefore hardly refracted(refractive sindex n=c/v≈0,99999)

X-rays

incoming lightwave

air

glass

Refractedwave

X-rays are hard to affect

Glass lens

0,01% - 1%reflected

Visible

Either:• not affected

or• small reflection

0-99%Go straight through

or are absorbed

X-rays

Utilize many reflections!


• Layer thicknesses: 3-7 atoms• Interface widths: 0.1-0.3 nm • Thickness precision: ~0.001 nm• Thickness repeatability: <0.00001 nm• Number of layers: 600-1200 layers

substrate

Reflected x-rays ”in phase”< 0.1%/interface

Example:incomingx-raysλ1=3.374 nm

Sc 0.977 nm

Cr 0.592 nm

Λ=1.569 nm

J. Birch et al

Multilayer X-ray mirror – What does it take?

X-ray reflectivity

Incoming angle ° 2θ° 2θ° 2θ° 2θ

1

10 -1

10 -2

10 -3

10 -4

10 -5

10 -6

Ref

lect

ivit

y

0 5 10 15 20

Simulated

(× 0.1)

Experiment

1

2

3

45

6 7

89

10

105 layer pairs with 2.56 nm Mo and 2.19 nm V + 21.3 nm Pd topp layer(16.2 atomic layers Mo and 14.4 atomic layers V)


X-ray Microscope using a Laser Plasma Source*

condenser(spheric multilayer mirror) specimen

objective lens(zone plate)

image (CCD)

*Prof. H. Hertz, Biomedical and X-ray Physics, Royal Institute of Technology, Stockholm

isotropic x-ray source

Spherical normal-incidence mirror is needed

lines: λλλλ1=3.374 nm (C VI emission)

λλλλ2=2.48 nm (N VII emission)

Deposition system for multilayer mirrors

Magnetron-sources

shutters

Mirror substrate

Vacuumchamber

coil


Magnetic coupling of processplasma to substrate coil

Mo/V, no coil, CrN/ScN, with coilI=5 A (~60 Gauss)

#ions#atoms= 0.1 - 1

#ions#molecules = 10 - 140

Advantages of sputter deposition of multilayers

+ +

Smoothening of ’islands’

Atoms and ions with relatively low velocity:

Densification

Smooth interfaces

We have these things under control


Problems during deposition af multilayers

+

Re-putteringof deposited atom

mixing atinterfaces

Creation of defects

Schematic picture ofthe atomic positions:

Atoms and ions with relatively high velocity:

Low adatom mobilityLow bulk diffusivity

High adatom mobilityLow bulk diffusivity

High adatom mobilityHigh bulk diffusivity or intermixing

a) b) c)

Low temp.Low kinetic energyLow flux af ions

Low temp. andLow kinetic energyHigh flux of ions

High temp. orHigh kinetic energy

How does the energetic ions/atoms affect our multilayer?

No good!

No good!

Low temp. andLow kinetic energyHigh flux av ions


Elektron microskopy of multilayer

100 layer pairs 2.5 nm Mo och 2.5 nm V

•Atomic resolution•Very smooth interfaces•Very abrupt interfaces

MeasurementSimulation

MeasurementSimulation

Soft X-ray reflectivity from our mirrors

High ion flux (φCr=7.1 and φSc=23.1) and low energy E=24 eV

λ=3.374 nm (for microskope optics) λ=3.115 nm

Peak reflectance R=5.47% at 76 ° Peak reflectance R=14.5% at 87.5 °

EXCELLENT RESULT(previous WR was 11)

F. Eriksson, G.A Johansson, H.M Hertz, E.M. Gullikson, and J. Birch, Opt. Lett. 28, 2494 (2003)


Excellent but…not good enough…

Rmeas=14.6 % , Rtheor=60%, ⇒ room for improvements!

How to get: abrupt and flat interfaces?

Low ion-energy⇓

abrupt interfaces

ackumulated roughness

low density

High ion-energy⇓

flat interfaces

dense structure

mixed interfaces

Jon-assisterad multilager deponering - MD simuleringar

Inga joner*:Eadatom = 0.1 eVEion=0 eV

• Vågigt • Taggigt• Akumulerad ojämnhet• (Diffusa mellanytor)

Låg-energi joner**:Eadatom = 0.1 eVEion = 3 eV (Xe

+)Ion/metal flux ratio F = 2

2 nm Cu/2 nm Ni/2 nm Cu/Ni(111), T= 300K, Normal incidence fluxes

• Minskad vågighet• Taggighet finns kvar• Minskad akumulerad ojämnhet• (Diffusa mellanytor)

* X. W. Zhou and H. N. G. Wadley, J. Appl. Phys, 84, 2301, 1998 ** X. W. Zhou and H. N. G. Wadley, J. Appl. Phys, 87, 2273, 2000*** X. W. Zhou and H. N. G. Wadley, J. Appl. Phys, 88, 5737, 2000

Effecter av jonflödet***:Eion = 14 eV (Ar

+)

• 3D yta undertrycks• Vågighet minskas


Interface Engineering - Modulated Ion Assistance

growth direction

+ ++

Eion

F. Eriksson, J. Birch, et al. in manuscript

”initial thicknesses” ~ a few atomic diameters

abrubt interface 0 eV

sputter sources

plasma

substrate

sputter sources

plasma

substrate

densification, flattening 24 eVabrubt interface 0 eV

sputter sources

plasma

substrate

densification, flattening 24 eV

Homogenous ion-assistance Tvo-step ion-assistanceion=24 eV) dinit=0.3 nm(Einit=6 eV e

- Efinal=24 eV)

Excellent! Exceptional!

Soft X-ray reflectivity - Latest results








X-ray Microscope using a Laser Plasma Source

condenser(spheric multilayer mirror) specimen

objective lens(zone plate)

image (CCD)

Prof. H. Hertz, Biomedical and X-ray Physics, Royal Institute of Technology, Stockholm

isotropic x-ray sourcelines: λλλλ1=3.374 nm (C VI emission)

λλλλ2=2.48 nm (N VII emission)

Spherical normal-incidence mirror is needed


Soft X-ray microscopy

2 µm

Silicate algae ”diatom” found in the 19:th century outside Stockholm(Göttingen Algensamlung)Picture taen by H. Hertz et. al. KTH, Stockholm, 2000

B4C/W multilayer mirror, R=0.5% (not ours…)

~100 nm

Cell-line cos-7 from green monkey

Images taken by H. Hertz et. al. KTH, Stockholm, 2000

Ordinary light mikroskopy X-ray microscope

B4C/W multilayer mirror R=0,5 % (not ours)

Soft X-ray microscopy




< 0.1 mm components





EUV lithography test stand

M1

C4

M3

M4

Camera chamber

Mask stagechamber Laser drive optics

C1 Xe gas

C3

Illuminatorenclosure

C2

LPP

M2

Wafer stage chamber

Wafer

λ=13.3 nmMo/Si multilayer mirrorsR=69% ⇒ ~5% through

Three consortia worldwide- USA- EU- Japan

Large uniform mirrors with high reflectance








Free Electron Laser

• femto - picosecond pulse lengths

• 6 orders of magnitude higher brightness than 3G synchrotron undulators

GeV electron LINAC

undulator

X-ray mirrors

e-recirculation

x-ray pulse

e.g., HASYLAB Tesla-facility, λ>6.0 nmSLAC-LCLS, λ>0.15 nm

Mirrors must withstand very high radiation power densities




• X-ray telescopy -solar observations

-deep space telescopy

- ”observations” of black holes




Röntgenteleskop

”TRACE”


Negativ spänningpå provet

Röntgentelekopbild av solen (TRACE)

171, 195 and 1700 Å wavelength bands

Röntgentelekopbild av solen (TRACE)


Framtidens teleskop

Hur bra är upplösningen - vinkeln mellan två urskiljbara objekt?

vinkel förbättringbågsek.(log)

Grottmänniska 100 --Galileo 3 1,5Hubble Telescope 0,1 3TRACE 0,1 3HIREX* 0,01 4MAXIM* 10-7 9

* Projekteras

”HIREX”

35 m


Simulerade röntgentelekopbilder

Simulerade röntgentelekopbilder


Simulerade röntgentelekopbilder med MAXIM

”MAXIM”


20 km

10 km

Soft X-ray Telescope for Deep Space Imaging

10-4 - 10-7 arcsec resolutionmakes imaging of stars andblack holes possible.

(Hubble: 0.1 arcsec)

From D. L. Windt, et al., Proc. SPIE, 4851, in press (2002)

Very large normal-incidencemirrors will be needed!!

Don’t forget to sign the participant list.

multilayer mirrors for x-rays - linköping university · "highlights in physics" 2005 by...

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