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Figure 3
Effectiveness of hydro­fluoric acid washing of stoichiometric silicon nitride windows. Vertical scan of a series of freshly made windows with different hydro­fluoric acid wash times showing changes in (a) O, (b) N and (c) F content via X-ray fluorescence. We note that both sides of the silicon frame are covered with silicon nitride, with silicon exposed only around the window on the etched side. This is apparent in the N K-edge profile, where the window area is bounded by two sharp reductions in N K-fluorescence. A 5 s or longer hydro­fluoric acid wash reduces the O K-edge fluorescence by over ∼50%, presumably removing the surface oxide layer and leaving bulk adsorbed O. Etching of the silicon nitride window is observed after 80 s through loss of the N K-fluorescence. Minimal residual F is seen, showing the water washing steps are sufficient.

Journal logoJOURNAL OF
SYNCHROTRON
RADIATION
ISSN: 1600-5775
Volume 28| Part 6| November 2021| Pages 1845-1849
https://doi.org/10.1107/S1600577521009942
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