Multilayer-coated micro-grating array for X-ray phase-contrast imaging

Susanna K. Lynch, Chian Liu, Lahsen Assoufid, Nicole Y. Morgan, Dumitru Mazilu, Eric Bennett, Camille K. Kemble, Han H. Wen

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

X-ray imaging techniques based on grating interferometers rely on transmission gratings to detect x-ray refraction and scattering in a sample. Gratings periods below 2 microns are challenging to realize due to the high aspect ratio of the structures. We propose a method to fabricate transmission gratings with sub-micron periods over centimeter areas by multilayer coating of a staircase (echelle) substrate. The advantage of this approach is the high aspect ratio of multilayer coating and the large area of the echelle substrate. The staircase pattern is etched on the surface of a silicon wafer through anisotropic etching. Multiple layers are deposited on the horizontal surfaces of the stairs by magnetron sputtering in a single run. The layers alternate between two materials of different absorption coefficients or refractive indices. The layer thickness d is designed to be (stair height)/2N, where 2N is the total number of layers. The incident xray beam is parallel to the layers and oblique to the wafer surface. Each stair of the echelle substrate forms a micro grating of period 2d, and the array of micro gratings together act as a single grating over a large area given the right continuity conditions. The grating period potentially can be below 100 nm. We present theoretical description of wave diffraction by the grating array, and results of the first fabrication test with magnetron sputtering deposition.

Original languageEnglish (US)
Title of host publicationEUV and X-Ray Optics
Subtitle of host publicationSynergy Between Laboratory and Space II
DOIs
StatePublished - Jun 14 2011
Externally publishedYes
EventEUV and X-Ray Optics: Synergy Between Laboratory and Space II - Prague, Czech Republic
Duration: Apr 20 2011Apr 21 2011

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume8076
ISSN (Print)0277-786X

Other

OtherEUV and X-Ray Optics: Synergy Between Laboratory and Space II
CountryCzech Republic
CityPrague
Period4/20/114/21/11

Keywords

  • CT
  • dark-field
  • grating
  • imaging
  • interferometer
  • multilayer
  • phase-contrast
  • x-ray

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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