High-efficiency silicon photodiode detector for sub-keV electron microscopy

Agata Sakic*, Gerard van Veen, Kees Kooijman, Patrick Vogelsang, Tom L.M. Scholtes, Wiebe B. de Boer, Jaber Derakhshandeh, Wim H.A. Wien, Silvana Milosavljevic, Lis K. Nanver

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

31 Citations (Scopus)


A silicon photodiode detector is presented for use in scanning electron microscopy (SEM). Enhanced imaging capabilities are achieved for sub-keV electron energy values by employing a pure boron (PureB) layer photodiode technology to deposit nanometer-thin photosensitive anodes. As a result, imaging using backscattered electrons is demonstrated for 50-eV electron landing energy values. The detector is built up of several closely packed photodiodes, and to obtain high scanning speed, each photodiode is engineered with low series resistance and low capacitance values. The low capacitance (< 3 pF/mm 2) is facilitated by thick, almost intrinsically-doped epitaxial layers grown to achieve the necessarily wide depletion regions. For the low series resistance, diode metallization has been patterned into a conductive grid directly on top of the nanometer-thin PureB-layer front-entrance window. Finally, a through-wafer aperture in the middle of the detector is micromachined for flexible positioning in the SEM system.

Original languageEnglish
Article number6261542
Pages (from-to)2707-2714
Number of pages8
JournalIEEE Transactions on Electron Devices
Issue number10
Publication statusPublished - 15 Aug 2012
Externally publishedYes


  • Backscattered electrons (BSEs)
  • Boron layer
  • Electron detector
  • Low-energy electrons
  • Silicon epitaxy
  • Silicon photodiode


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