Hybrid Pixel Detectors for Next-Generation Diffraction Cameras in Scanning Electron Microscopy

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"Electron Backscatter Diffraction (EBSD) is a Scanning Electron Microscopy (SEM) technique to analyse the properties of crystalline materials at scales from the nano- and micro-, up to the macroscopic level. It uses a sensitive camera to record the Electron Backscatter Diffraction Pattern (EBSP) generated at each of a series of nano-scale spots on a specimen as it is ""mapped"" by the focussed electron beam.EBSD is an important tool for research and development in many fields, including: metallurgy; semiconductors; and geology. In many EBSD experiments the sensitivity and speed of analysis is limited by the cameras currently available, and there is a demonstrated need for improvement. Increased sensitivity of the camera would allow for the capture of high-quality EBSPs with lower electron doses applied to the specimen. Development of a higher-sensitivity EBSD camera will allow for higher-speed operation and hence enhance the appeal of EBSD across all applications. It will open new areas of both academic and industrial interest, including for beam-sensitive materials that have not so far been amenable to EBSD.Current EBSD cameras use Indirect electron Detection (IeD) with sensitivity limited by inefficient coupling of photons (generated by electrons at a phosphor screen) via optics to the image sensor. Instead, Direct electron Detection (DeD) at the image sensor (i.e. removing the inefficient optics) can enhance sensitivity and may be realised by the use of a Hybrid Pixel Detector (HPD) comprising a semiconducting sensor bonded to an electron-counting Application Specific Integrated Circuit (ASIC) such as those in the Medipix family. The project seeks to build on our early work and develop an HPD based on latest-generation Medipx4 ASIC, optimised for EBSD and with substantially enhanced sensitivity."