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Scattering Techniques. Lecture 17 G.J. Mankey [email protected] Elastic-no energy loss. Light Reflectometry Ellipsometry* X-rays Diffraction* Reflectometry Electrons Diffraction* Neutrons Diffraction Small Angle Neutron Scattering* Reflectometry*.

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Scattering techniques l.jpg

Scattering Techniques

Lecture 17

G.J. Mankey

[email protected]


Scattering l.jpg

Elastic-no energy loss.

Light

Reflectometry

Ellipsometry*

X-rays

Diffraction*

Reflectometry

Electrons

Diffraction*

Neutrons

Diffraction

Small Angle Neutron Scattering*

Reflectometry*

Inelastic-energy loss to excitation.

Light

Raman*

Brillouin*

X-rays

EXAFS*

Electrons

HREELS*

Ion Scattering*

Neutrons

Inelastic Neutron Scattering

Scattering


Inelastic light scattering l.jpg

Inelastic Light Scattering

  • Brilloin Scattering-Scattering from an acoustic phonon.

  • Raman Scattering-Scattering from an optical phonon.


Exafs l.jpg

EXAFS

  • Fine structure in the vicinity of the adsorption edges contains information about the local environment of the chemical species.

ref: Prof. Brian Tonner, UCF


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X-Ray Absorption

  • Photon energy is tuned to elemental core level.

  • Technique probes chemical composition.

  • Requires a synchrotron x-ray source and monochromator.

ref: Prof. Brian Tonner, UCF


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X-Ray Adsorption Measurements

  • Each method of measurement has advantages specific to the detection method.

ref: Prof. Brian Tonner, UCF


Electron inelastic mean free path l.jpg

The electron probing depth follows the "Universal Curve."

This is also true for electron spectroscopies.

The curve has the form:

Where A and B are material dependent parameters.

To first approximation, A and B are the same for all metals.

Electron Inelastic Mean Free Path

ref: Prof. Brian Tonner, UCF


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Information in XAS

  • The range of energy losses probed give different information about the local environment of the chemical species with the particular adsorption edge.

ref: Prof. Brian Tonner, UCF


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HREELS

Ref: http://nano.kaist.ac.kr/2002ch607/Ch5-VIb.pdf


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Electron Scattering Mechanism

Ref: http://nano.kaist.ac.kr/2002ch607/Ch5-VIb.pdf


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HREELS Example

Ref: http://nano.kaist.ac.kr/2002ch607/Ch5-VIb.pdf


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Ion Scattering Spectroscopy

Ref: http://nano.kaist.ac.kr/2002ch607/Ch5-VIb.pdf


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Properties of Neutrons

ref: SNS Website


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Neutron Scattering

ref: T.E. Mason


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Reciprocal Space

ref: T.E. Mason


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Small Angle Neutron Scattering

  • Neutrons probe length scales comparable to TEM and soft x-rays.

  • Neutrons are a gentle probe since their energies are of the order of a few milli electron volts as opposed to hundreds to thousands of electron volts for x-rays and electrons.

ref: Charles Glinka, NIST


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Contrast

  • The contrast mechanism for neutrons scattering length density rather than electron density for x-rays.

ref: T.E. Mason


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SANS Instrumentation

  • Nanoscale lengths are probed.

ref: Charles Glinka, NIST


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Neutrons Probe Magnetic Structure

  • The magnetic scattering length in Fe is 1/3 of the chemical scattering length, so SANS also probes magnetic structures.

ref: Charles Glinka, NIST


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Neutron Reflectometry

  • Q-dependent reflectivity gives interfacial roughness and correlation length.

  • Polarized reflectometry yields magnetic roughness.

ref: T.E. Mason


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