A New High Performance Detector for Electron Energy Loss Spectroscopy

Abstract

<jats:p>The serial detectors traditionally used in Electron Energy Loss Spectroscopy (EELS) have mostly been replaced by parallel detection systems, for reasons of efficiency and ease of use. So far most parallel detection systems have been based on fiber or lens coupled Photo Diode Array (PDA). Although these systems have proven satisfactory they have some limitations: 1) high readout noise, 2) limited correction for gain variations and 3) point spread function or cross talk between channels all of which effects the ultimate sensitivity and resolution. This paper discusses a newly developed parallel detector for EELS based on a CCD and a new type of scintillator and fiber technology. The new detector shows large improvements in all areas of performance.</jats:p><jats:p>The sensitivity of a detector is limited by the readout noise at low incident electron dose and the gain correction at high dose. Both these areas have been addressed in the new design. The readout noise is equivalent to approximately 1/2 a primary electron, about 40 times better than a typical PDA.</jats:p>

Detecting single atoms of calcium and iron in biological structures by electron energy‐loss spectrum‐imaging

“…Elemental mapping was performed using a VG Microscopes HB501 STEM coupled to a Gatan parallel‐detection electron spectrometer (Krivanek et al ., 1987), which had been modified into the Gatan UHV Enfina system to incorporate a cooled 1340 × 100‐channel CCD detector (Brink et al ., 2000; Hunt et al ., 2001). Specimens were cooled to −160 °C to minimize mass loss or contamination under electron irradiation.…”

Detection Limits for Electron Energy-Loss Spectroscopy in Biology

“…Advances in electron energy loss spectroscopy (EELS), both in the scanning transmission electron microscope (STEM) and the energy-filtering transmission electron microscope (EFTEM), have created new opportunities for biological microanalysis. In particular, more sensitive detectors have improved detection limits [1][2][3][4][5], and spectrum-imaging software for acquiring EELS data pixel by pixel has increased flexibility for mapping the distributions of biologically important elements [6][7][8][9].…”

Analysis of Biological Structures by Electron Energy Loss Spectroscopy and Imaging

“…3 ' 4 To obtain such results, the electron detector should have a detective quantum efficiency close to unity and a well behaved point-spread function; such design features are now available with a cooled charge-couple device (CCD) array. 5 The energy-filtering transmission electron microscope (EFTEM) provides a complementary approach to mapping elements occurring at higher concentrations but distributed over larger regions of the specimen. Use of an optimized CCD detector in the EFTEM now enables accurate quantitation ih addition to high analytical sensitivity, albeit not at the single atom level.…”

“…It is anticipated that the quality of such data will also be greatly improved by using an optimized CCD detector in place of a photodiode array. 5 Spectrum-imaging in the EFTEM promises to improve greatly the accuracy of quantifying elemental concentrations obtained in the fixed beam instrument. Instead of acquiring elemental maps using one or two pre-edge windows and one post-edge window, an entire energy-loss spectrum can be obtained at each pixel, which allows more sophisticated processing and increases reliability of the resulting elemental images.…”