Center for Materials for Information Technology an NSF Materials Science and Engineering Center Scattering Techniques Lecture 17 G.J. Mankey

Center for Materials for Information Technology an NSF Materials Science and Engineering Center Scattering 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

Center for Materials for Information Technology an NSF Materials Science and Engineering Center Inelastic Light Scattering Brilloin Scattering-Scattering from an acoustic phonon. Raman Scattering-Scattering from an optical phonon.

Center for Materials for Information Technology an NSF Materials Science and Engineering Center 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

Center for Materials for Information Technology an NSF Materials Science and Engineering Center 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

Center for Materials for Information Technology an NSF Materials Science and Engineering Center X-Ray Adsorption Measurements Each method of measurement has advantages specific to the detection method. ref: Prof. Brian Tonner, UCF

Center for Materials for Information Technology an NSF Materials Science and Engineering Center Electron Inelastic Mean Free Path 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. ref: Prof. Brian Tonner, UCF

Center for Materials for Information Technology an NSF Materials Science and Engineering Center 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

Center for Materials for Information Technology an NSF Materials Science and Engineering Center HREELS Ref:

Center for Materials for Information Technology an NSF Materials Science and Engineering Center Electron Scattering Mechanism Ref:

Center for Materials for Information Technology an NSF Materials Science and Engineering Center HREELS Example Ref:

Center for Materials for Information Technology an NSF Materials Science and Engineering Center Ion Scattering Spectroscopy Ref:

Center for Materials for Information Technology an NSF Materials Science and Engineering Center Properties of Neutrons ref: SNS Website

Center for Materials for Information Technology an NSF Materials Science and Engineering Center Neutron Scattering ref: T.E. Mason

Center for Materials for Information Technology an NSF Materials Science and Engineering Center Reciprocal Space ref: T.E. Mason

Center for Materials for Information Technology an NSF Materials Science and Engineering Center 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

Center for Materials for Information Technology an NSF Materials Science and Engineering Center Contrast The contrast mechanism for neutrons scattering length density rather than electron density for x-rays. ref: T.E. Mason

Center for Materials for Information Technology an NSF Materials Science and Engineering Center SANS Instrumentation Nanoscale lengths are probed. ref: Charles Glinka, NIST

Center for Materials for Information Technology an NSF Materials Science and Engineering Center 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

Center for Materials for Information Technology an NSF Materials Science and Engineering Center Neutron Reflectometry Q-dependent reflectivity gives interfacial roughness and correlation length. Polarized reflectometry yields magnetic roughness. ref: T.E. Mason