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30 April 2009 Microstructured optical arrays for smart x-ray optics
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The Smart X-ray Optics (SXO) programme is developing advanced active-adaptive optics for X-rays. There are two main themes: large optics for applications in astronomy and small scale optics for micro-probing of biological cells and tissue samples using Ti or Cr Kα radiation (4.5keV and 5.4keV, respectively) in studies related to radiation induced cancers. For the latter objective, microstructured optical arrays (MOAs) have been proposed. These consist of an array of channels deep etched in silicon. They use grazing incidence reflection to focus the X-rays through consecutive aligned arrays of channels, ideally reflecting once off a channel wall in each array. Bending the arrays allows variable focal length. The adaptivity is achieved by flexing the arrays using PZT (Lead Zirconate Titanate)-based piezo actuators. The array bending has been modelled using finite element analysis (FEA) and the results showed that for reasonable efficiency, the wall roughness of the channels should not exceed 2nm. This paper describes two techniques of fabrication the MOAs: dry etching and wet etching. The first method requires a special equipment called "inductively coupled plasma" (ICP) using Bosch processes that are designed to produce features with a high aspect ratio with vertical walls. The second method involves using an alkaline solution for etching <110> silicon wafers. This type of wafer was selected because of the large wet etch ratio between the (111) and (100) planes that leads to smooth vertical walls. For our application tetra-methyl-ammonium hydroxide (TMAH) was used as it is fully compatible with CMOS integrated circuit processes.
© (2009) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Camelia Dunare, William Parkes, Tom Stevenson, Alan Michette, Slawka Pfauntsch, Shahin Sahraei, Matthew Shand, Dou Zhang, Daniel Rodriguez Sanmartin, Tim Button, Charlotte Feldman, Richard Willingale, Peter Doel, Hongchang Wang, and Ady James "Microstructured optical arrays for smart x-ray optics", Proc. SPIE 7360, EUV and X-Ray Optics: Synergy between Laboratory and Space, 736015 (30 April 2009);


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