Active pixel sensor array as a detector for electron microscopy

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• 作者：Milazzo ; Anna-Clare ; Leblanc ; Philippe ; Duttweiler ; Fred ; Jin ; Liang ; Bouwer ; James C. ; Peltier ; Steve ; et. al.
• 关键词：Active pixel sensor ; Detectors ; Electron microscopy ; Cryo-EM ; Signal-to-noise ratio ; Spatial resolution
• 刊名：Ultramicroscopy
• 出版年：2005
• 出版时间：September, 2005
• 年：2005
• 卷：104
• 期：2
• 页码：152-159
• 全文大小：358 K

文摘

A new high-resolution recording device for transmission electron microscopy (TEM) is urgently needed. Neither film nor CCD cameras are systems that allow for efficient 3-D high-resolution particle reconstruction. We tested an active pixel sensor (APS) array as a replacement device at 200, 300, and 400 keV using a JEOL JEM-2000 FX II and a JEM-4000 EX electron microscope. For this experiment, we used an APS prototype with an area of 64×64 pixels of 20 μm×20 μm pixel pitch. Single-electron events were measured by using very low beam intensity. The histogram of the incident electron energy deposited in the sensor shows a Landau distribution at low energies, as well as unexpected events at higher absorbed energies. After careful study, we concluded that backscattering in the silicon substrate and re-entering the sensitive epitaxial layer a second time with much lower speed caused the unexpected events. Exhaustive simulation experiments confirmed the existence of these back-scattered electrons. For the APS to be usable, the back-scattered electron events must be eliminated, perhaps by thinning the substrate to less than 30 μm. By using experimental data taken with an APS chip with a standard silicon substrate (300 μm) and adjusting the results to take into account the effect of a thinned silicon substrate (30 μm), we found an estimate of the signal-to-noise ratio for a back-thinned detector in the energy range of 200–400 keV was about 10:1 and an estimate for the spatial resolution was about 10 μm.