Fabrication of nanocrystalline diamond x-ray nano-focusing optics
In a collaboration between the Diamond Light Source (Synchrotron) and the Bristol Diamond Group we fabricated refractive optics for focusing high-energy X-ray radiation produced at synchrotron facilities. X-ray optics made from diamond are almost transparent, are very strong and are subject to very low thermal expansion. Therefore, they will be able to withstand the powerful beams generated by 3rd and 4th-generation light sources without compromising brilliance. We have fabricated and tested a nanocrystalline diamond (NCD) low-absorbing X-ray compound refractive lens (CRL) using a moulding technique. With this method, high-quality Si moulds are fabricated using e-beam-written photolithographic etching, and then NCD is deposited using MWCVD at a high growth rate. The Si mould is then removed in acid, and the resulting freestanding diamond CRL tested in the synchrotron beam-line.
SEM images of the diamond grown into the Si moulds.
One of these CRLs achieved a focus spot-size of ~140 nm in a 20 keV X-ray beam at a distance of about 20 cm, which is close to the world record for the smallest X-ray spot-size ever achieved for a beam as powerful as this. With improvements in seeding and etching, this spot-sized could be reduced even further.
SEM images of the freestanding nanocrystalline diamond CRLs after silicon etch and removal.
Fabrication of a non-absorbing, high-aperture lens with nano-focusing capabilities will be achieved when the material uniformity, seeding and lens robustness has been improved. We are now targeting the improvement of diamond growth and optimisation of lens structures using modified designs and selective diamond nucleation. This should reduce self-shadowing during deposition and increase depth of fill to allow us to fabricate higher aspect ratio lens structures.
Related Papers
- L. Alianelli, K.J.S. Sawhney, A. Malik, O.J.L. Fox, P.W. May, R. Stevens, I.M. Loader, M.C. Wilson, "A planar refractive x-ray lens made of nano-crystalline diamond", J. Appl. Phys., 108, 123107 (2010).
- A.M. Malik, O.J.L. Fox, L. Alianelli, A.M. Korsunsky, R. Stevens, I.M. Loader, M.C. Wilson, I. Pape, K.J.S. Sawhney and P.W. May, "Deep reactive ion etching of silicon moulds for the fabrication of diamond x-ray focusing lenses", J. Micromech. Microeng. 23 (2013) 125018
- O.J.L. Fox, L. Alianelli, A.M. Malik, I. Pape, P.W. May, K.J.S. Sawhney, "Nanofocusing optics for synchrotron radiation made from polycrystalline diamond", Optics Express 22 (2014) 7657-68.