Electrostatic Shutter in EMs
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For most economical GIF systems, recording low-loss and core-loss spectra under the same conditions is extremely challenging, since the acquisiton time required for a good SNR (signal to noise ratio) in the core-loss spectrum is usually not short enough to avoid saturation of the signal from the ZLP (zero-loss peak). Therefore, in practice, it is necessary to sacrifice the SNR in the core-loss signal, or utilize a spectrometer system that has an ultrafast electrostatic shutter installed.

Fortunately, Gatan energy-loss spectrometers have been improved with an ultrafast electrostatic shutter so that we are able to record the entire spectrum, including both the low-loss and core-loss regions almost simultaneously, in milliseconds. The GIF (Gatan imaging filter) Quantum employs fifth-order aberration correction, a 9-mm entrance aperture, faster CCD readout, and a 1-μs electrostatic shutter to allow simultaneous recording of the low-energy-loss and core-loss regions of a spectrum.

Figure 3932 shows the schematic illustration of a STEM spectrum imaging system together with a specially designed spectrometer that has an electrostatic shutter. The focused electron probe is scanned across the specimen and a couple of post-specimen coils is used to descan. At each pixel, an extended range of the energy-loss spectrum is selected by the voltage-scan module (VSM) and is acquired by a parallel-recording spectrometer. The electrostatic shutter allows fast switching between the low-loss and core-loss regions of the spectrum.

Schematic illustration of a STEM spectrum imaging system together with a specially designed spectrometer that has an electrostatic shutter

Figure 3932. Schematic illustration of a STEM spectrum imaging system together with a specially designed spectrometer that has an electrostatic shutter.

 

 

 

 

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