Development of nanocrystalline diamond windows for application in synchrotron beamlines

A multistep growth and masking method allowed developing windows with controlled geometry inside a silicon frame. In this paper, we present a new method to produce nanocrystalline diamond windows with thickness of about 200 nm to 40 μm, with different areas and shapes (circular, rectangular and rounded rectangle). The nanocrystalline diamond (NCD) films deposited on a silicon substrate (100) p-type, had a nucleation density of about 1011 part/cm2. Electrostatic self-assembly of nanodiamond seeds (4 nm powder) improved nucleation. Silicon anisotropic etching reveals the window geometry. The high nucleation density enabled smooth surfaces on both sides without the need for polishing the window. Pressure tests were performed in windows of varying thickness. The windows with thickness larger than 10 μm supported a pressure gradient of 1 atm.

► Developed freestanding nanocrystalline diamond windows.
► High nucleation densities (1011 part/cm2).
► Excellent optical quality.
► Windows with very low roughness without the need for polishing.
► Lithography process control in silicon.