Detector, linear capacitor

The most advanced chip-based ion detectors are the microfabricated Faraday cup arrays fabricated by Darling of Washington University [10], used with a compact linear dispersion magnetic mass spectrograph. Deep reactive ion etching of silicon was used to form high-aspect ratio trenches, which were then oxidized and metallized to form an array of independently addressable MOS capacitors as shown in Fig. 3c. Detector arrays were constructed with up to 256 elements and with pitches down to 150 pm, and the arrays have been combined with an electronic multiplexer to allow serial readout. 

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