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Silicon nitride transmission X-ray mirrors.

Cornaby S, Bilderback DH - J Synchrotron Radiat (2008)

Bottom Line: Transmission X-ray mirrors have been fabricated from 300-400 nm-thick low-stress silicon nitride windows of size 0.6 mm x 85 mm.The energy cut-off can be adjusted from 8 to 12 keV at an angle of 0.26 degrees to 0.18 degrees , respectively.The observed mirror transmittance was above 80% for a 300 nm-thick film.

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Affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA.

ABSTRACT
Transmission X-ray mirrors have been fabricated from 300-400 nm-thick low-stress silicon nitride windows of size 0.6 mm x 85 mm. The windows act as a high-pass energy filter at grazing incidence in an X-ray beam for the beam transmitted through the window. The energy cut-off can be selected by adjusting the incidence angle of the transmission mirror, because the energy cut-off is a function of the angle of the window with respect to the beam. With the transmission mirror at the target angle of 0.22 degrees , a 0.3 mm x 0.3 mm X-ray beam was allowed to pass through the mirror with a cut-off energy of 10 keV at the Cornell High Energy Synchrotron Source. The energy cut-off can be adjusted from 8 to 12 keV at an angle of 0.26 degrees to 0.18 degrees , respectively. The observed mirror transmittance was above 80% for a 300 nm-thick film.

No MeSH data available.


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Calculated transmission of 100 nm-, 300 nm- and 500 nm-thick silicon nitride membrane at 0.22° with 5 nm r.m.s. roughness on the surfaces. A 200 µm aluminium attenuation filter is also shown for comparison. Calculated at http://www-cxro.lbl.gov/.
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fig2: Calculated transmission of 100 nm-, 300 nm- and 500 nm-thick silicon nitride membrane at 0.22° with 5 nm r.m.s. roughness on the surfaces. A 200 µm aluminium attenuation filter is also shown for comparison. Calculated at http://www-cxro.lbl.gov/.

Mentions: We wanted to have the membrane as thin as possible. Fig. 2 ▶ shows the predicted transmission curves for membranes of 100 nm, 300 nm and 500 nm thickness, at 0.22° and with 5 nm r.m.s. of roughness (Henke et al., 1995–2007 ▶). The TM has a higher transmission efficiency than the aluminium absorber. The TM also has a desirable sharp change in its energy-response curve. The thinner windows have better transmission properties, especially near the cut-off energy. Silicon nitride windows are very strong for their thickness (100–1000 µm), but the windows become more fragile when the membrane is thinner or has a larger window size. We tried to make both 100 nm- and 300 nm-thick windows. For a window size of 0.6 mm × 85 mm, none of the 100 nm films survived the etching process. The 300 nm-thick windows, however, had roughly a 50% survival rate from the fabrication etching process.


Silicon nitride transmission X-ray mirrors.

Cornaby S, Bilderback DH - J Synchrotron Radiat (2008)

Calculated transmission of 100 nm-, 300 nm- and 500 nm-thick silicon nitride membrane at 0.22° with 5 nm r.m.s. roughness on the surfaces. A 200 µm aluminium attenuation filter is also shown for comparison. Calculated at http://www-cxro.lbl.gov/.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2631103&req=5

fig2: Calculated transmission of 100 nm-, 300 nm- and 500 nm-thick silicon nitride membrane at 0.22° with 5 nm r.m.s. roughness on the surfaces. A 200 µm aluminium attenuation filter is also shown for comparison. Calculated at http://www-cxro.lbl.gov/.
Mentions: We wanted to have the membrane as thin as possible. Fig. 2 ▶ shows the predicted transmission curves for membranes of 100 nm, 300 nm and 500 nm thickness, at 0.22° and with 5 nm r.m.s. of roughness (Henke et al., 1995–2007 ▶). The TM has a higher transmission efficiency than the aluminium absorber. The TM also has a desirable sharp change in its energy-response curve. The thinner windows have better transmission properties, especially near the cut-off energy. Silicon nitride windows are very strong for their thickness (100–1000 µm), but the windows become more fragile when the membrane is thinner or has a larger window size. We tried to make both 100 nm- and 300 nm-thick windows. For a window size of 0.6 mm × 85 mm, none of the 100 nm films survived the etching process. The 300 nm-thick windows, however, had roughly a 50% survival rate from the fabrication etching process.

Bottom Line: Transmission X-ray mirrors have been fabricated from 300-400 nm-thick low-stress silicon nitride windows of size 0.6 mm x 85 mm.The energy cut-off can be adjusted from 8 to 12 keV at an angle of 0.26 degrees to 0.18 degrees , respectively.The observed mirror transmittance was above 80% for a 300 nm-thick film.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA.

ABSTRACT
Transmission X-ray mirrors have been fabricated from 300-400 nm-thick low-stress silicon nitride windows of size 0.6 mm x 85 mm. The windows act as a high-pass energy filter at grazing incidence in an X-ray beam for the beam transmitted through the window. The energy cut-off can be selected by adjusting the incidence angle of the transmission mirror, because the energy cut-off is a function of the angle of the window with respect to the beam. With the transmission mirror at the target angle of 0.22 degrees , a 0.3 mm x 0.3 mm X-ray beam was allowed to pass through the mirror with a cut-off energy of 10 keV at the Cornell High Energy Synchrotron Source. The energy cut-off can be adjusted from 8 to 12 keV at an angle of 0.26 degrees to 0.18 degrees , respectively. The observed mirror transmittance was above 80% for a 300 nm-thick film.

No MeSH data available.


Related in: MedlinePlus