Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Feedstock verification of silicon boules for SRM640g

Diffraction pattern from unstrained float-zone silicon

Comparison of the left-beam and right-beam diffraction patterns from float-zone silicon.  The central peak offset is related to the lattice spacing difference from the transfer crystal. The horizontal scale is in raw angle-interferometer fringes, where 1 fringe is roughly 0.775 μrad (0.16 second of arc).  The instrumental angular resolution is approximately 1 nrad.

The incoming intrinsic float-zone silicon boules which will become SRM640g were verified for quality by measuring their lattice spacing.  The ability to make such a measurement assured the original crystal is nearly perfect, with very low strain and defect density.  The sharp, central fringe in the image will not appear on a crystal with significant imperfections.

Created April 4, 2023, Updated April 17, 2023