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Detective quantum efficiency of electron area detectors in electron microscopy.

McMullan G, Chen S, Henderson R, Faruqi AR - Ultramicroscopy (2009)

Bottom Line: Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors with those of detectors based on new technology.In the case of film, the effects of electron backscattering from both the holder and the plastic support have been investigated.We also show that part of the response of the emulsion in film comes from light generated in the plastic support.

View Article: PubMed Central - PubMed

Affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB20QH, UK. gm2@mrc-lmb.cam.ac.uk

ABSTRACT
Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors with those of detectors based on new technology. We present MTF and DQE measurements for four types of detector: Kodak SO-163 film, TVIPS 224 charge coupled device (CCD) detector, the Medipix2 hybrid pixel detector, and an experimental direct electron monolithic active pixel sensor (MAPS) detector. Film and CCD performance was measured at 120 and 300 keV, while results are presented for the Medipix2 at 120 keV and for the MAPS detector at 300 keV. In the case of film, the effects of electron backscattering from both the holder and the plastic support have been investigated. We also show that part of the response of the emulsion in film comes from light generated in the plastic support. Computer simulations of film and the MAPS detector have been carried out and show good agreement with experiment. The agreement enables us to conclude that the DQE of a backthinned direct electron MAPS detector is likely to be equal to, or better than, that of film at 300 keV.

No MeSH data available.


Schematic of MAPS CMOS detector. The pixel spacing is determined by the spacing between diodes formed by the  well doped areas indicated in blue. The division into three layers used in the simulations is indicated and consists of: (a) passivation and heavily doped wells; (b) sensitive layer consisting of the lightly doped epilayer; and (c) heavily doped substrate. The track of an incident electrons is shown illustrating the problem with backscattering from the substrate in a non-backthinned detector. The diffusive collection by the reverse biased  well diodes of mobile electrons generated in electron-hole pair excitations is indicated.
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fig14: Schematic of MAPS CMOS detector. The pixel spacing is determined by the spacing between diodes formed by the well doped areas indicated in blue. The division into three layers used in the simulations is indicated and consists of: (a) passivation and heavily doped wells; (b) sensitive layer consisting of the lightly doped epilayer; and (c) heavily doped substrate. The track of an incident electrons is shown illustrating the problem with backscattering from the substrate in a non-backthinned detector. The diffusive collection by the reverse biased well diodes of mobile electrons generated in electron-hole pair excitations is indicated.

Mentions: A schematic cross-section of a MAPS detector is shown in Fig. 14. The complication found with incident electrons of energies typically used in electron microscopy, from backscattering from the substrate, is also illustrated. The MAPS detector consists of a heavily p-doped substrate supporting a lightly p-doped epilayer onto which heavily doped n- and p-well areas are deposited. The n-well areas form reverse biased diodes whose voltages are set and readout with the aid of nMOS transistors fabricated on adjacent p-well areas. Further layers containing inter-layer dielectrics and the metallic interconnects are deposited on top of this and the whole detector is capped with a final passivation layer.


Detective quantum efficiency of electron area detectors in electron microscopy.

McMullan G, Chen S, Henderson R, Faruqi AR - Ultramicroscopy (2009)

Schematic of MAPS CMOS detector. The pixel spacing is determined by the spacing between diodes formed by the  well doped areas indicated in blue. The division into three layers used in the simulations is indicated and consists of: (a) passivation and heavily doped wells; (b) sensitive layer consisting of the lightly doped epilayer; and (c) heavily doped substrate. The track of an incident electrons is shown illustrating the problem with backscattering from the substrate in a non-backthinned detector. The diffusive collection by the reverse biased  well diodes of mobile electrons generated in electron-hole pair excitations is indicated.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2864625&req=5

fig14: Schematic of MAPS CMOS detector. The pixel spacing is determined by the spacing between diodes formed by the well doped areas indicated in blue. The division into three layers used in the simulations is indicated and consists of: (a) passivation and heavily doped wells; (b) sensitive layer consisting of the lightly doped epilayer; and (c) heavily doped substrate. The track of an incident electrons is shown illustrating the problem with backscattering from the substrate in a non-backthinned detector. The diffusive collection by the reverse biased well diodes of mobile electrons generated in electron-hole pair excitations is indicated.
Mentions: A schematic cross-section of a MAPS detector is shown in Fig. 14. The complication found with incident electrons of energies typically used in electron microscopy, from backscattering from the substrate, is also illustrated. The MAPS detector consists of a heavily p-doped substrate supporting a lightly p-doped epilayer onto which heavily doped n- and p-well areas are deposited. The n-well areas form reverse biased diodes whose voltages are set and readout with the aid of nMOS transistors fabricated on adjacent p-well areas. Further layers containing inter-layer dielectrics and the metallic interconnects are deposited on top of this and the whole detector is capped with a final passivation layer.

Bottom Line: Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors with those of detectors based on new technology.In the case of film, the effects of electron backscattering from both the holder and the plastic support have been investigated.We also show that part of the response of the emulsion in film comes from light generated in the plastic support.

View Article: PubMed Central - PubMed

Affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB20QH, UK. gm2@mrc-lmb.cam.ac.uk

ABSTRACT
Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors with those of detectors based on new technology. We present MTF and DQE measurements for four types of detector: Kodak SO-163 film, TVIPS 224 charge coupled device (CCD) detector, the Medipix2 hybrid pixel detector, and an experimental direct electron monolithic active pixel sensor (MAPS) detector. Film and CCD performance was measured at 120 and 300 keV, while results are presented for the Medipix2 at 120 keV and for the MAPS detector at 300 keV. In the case of film, the effects of electron backscattering from both the holder and the plastic support have been investigated. We also show that part of the response of the emulsion in film comes from light generated in the plastic support. Computer simulations of film and the MAPS detector have been carried out and show good agreement with experiment. The agreement enables us to conclude that the DQE of a backthinned direct electron MAPS detector is likely to be equal to, or better than, that of film at 300 keV.

No MeSH data available.