X-ray mirrors with sub-nanometre figure errors obtained by differential deposition of thin WSi2 films

Differential deposition by DC magnetron sputtering was applied to correct for figure errors of X-ray mirrors to be deployed on low-emittance synchrotron beamlines. During the deposition process, the mirrors were moved in front of a beam-defining aperture and the required velocity profile was calculated using a deconvolution algorithm. The surface figure was characterized using conventional off-line visible-light metrology instrumentation (long trace profiler and Fizeau interferometer) before and after the deposition. WSi2 was revealed to be a promising candidate material since it conserves the initial substrate surface roughness and limits the film stress to acceptable levels. On a 300   mm-long flat Si mirror the average height errors were reduced by a factor of 20 down to 0.2   nm root mean square. This result shows the suitability of WSi2 for differential deposition. Potential promising applications include the upgrade of affordable, average-quality substrates to the standards of modern synchrotron beamlines.

Source: Journal of Synchrotron Radiation - May 30, 2023 Category: Physics Authors: Bras, P. Morawe, C. Labour é , S. Perrin, F. Vivo, A. Barrett, R. Tags: X-ray optics figure correction differential deposition surface roughness film   stress off-line metrology Fizeau stitching long trace profiler magnetron sputtering research papers Source Type: research