Direct electron counting detector for EELS imaging. MerlinEELS significantly improves EELS in two key metrics: electron counting - to get the maximum signal to noise ratio and, high framerates independent of detection noise - to mitigate sample drifts.


Overview of the MerlinEELS

Utilising a direct electron counting detector in EELS offers significant advantages to our customers. MerlinEELS detector offers a high dynamic range for up to 16M counts within one pixel. The detector has 256 pixels in the dispersion dimension, therefore if evenly spread it can collect well above a billion counts per channel. On top of this, the detector offers zero read-out noise and zero dead time for up to 12-bit imaging. The advantages these two properties bring to EELS are further examined below.


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  • 1024 x 256 sized hybrid pixel detector consisting of 4 Medipix3 chips
  • 3600 fps at 6-bit
  • Much higher fps possible with ROI
  • Ability to generate random arbitrary scans
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Firstly, the high dynamic range allows our users to collect the high dose zero-loss peak together with the low-loss signals in a single spectrum. In our example image, this was done for LaMnO3 and SrTiO3 interface. Standard background filtered EELS peak images, dark-field, and ZLP images are extracted from the 3D spectrum information.

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The very interesting second example which demonstrates the lack of readout noise is the set of the high core-loss images from the same material. The MerlinEELS detector was able to collect energy loss spectra at around the 5 kV mark from the same material interface between LaMnO3 and SrTiO3. This allowed us to produce atomically localised EELS data and even recognise a small dispersion of Lantanum atoms intro Strontium Titanate. The image also demonstrates the level of signal present at these high loss areas – a single probe position (red graph) cannot resolve any edge present with electron counts being 0 to 12 for 10 ms dwell time. Once we sum 3×3 positions (blue graph), the Lantanum L3 edge becomes visible and even more so for a unit cell average (orange graph). For comparison, we have summed up the data from the whole sample also showing the Titanium K edge signal (green graph).

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MerlinEELS detector fully installed at SuperSTEM in Daresbury, UK on the Nion UltraSTEM 100

Applications for the MerlinEELS

Quantum Detectors systems are designed with you in mind. We want to help you achieve results, here are some of the applications this system is capable of.



Modern fast framing electron detectors like MerlinEM allow practical imaging of a full distribution of electrons for each probe position in a scanning transmission electron microscope. The most common name of the technique is 4D-STEM, however, scanned diffraction or momentum resolved STEM are also used.

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Features of the MerlinEELS

Rapid Gapless Readout and high dynamic range

Within each pixel are two counters, which can be used simultaneously to give gapless readout – whilst one counter reads, the other reads out. This unique approach is of particular importance for beam-sensitive samples – there is no gap in time for readout so every part of the exposure to the sample is being read and recorded. This feature and the speed of the detector can be used to record gapless multi-frame films of dynamic effects and it can be also used to collect diffraction sample tilt series by continuous rotation of the goniometer, without loss of any electron data to the read-out. Due to the electron counting approach of the detection system as well as the fully digital readout, MerlinEELS adds zero noise allowing a Signal to Noise Ratio (SNR) within a single frame as high as 16.7 million to zero.

Region of Interest

The ROI Rows function allows a dramatic increase in speed of readout. The user can select how many Rows the software will read from the detector. The default value, 256, means that the whole chip will be read out. Selecting a different value will result in a rectangle image of N x 256 pixels where N can be N ∈ {4, 8, 16, 32, 64, 128}. The position of the Rows is fixed to the inner edge of the detector due to the architecture of the chip.  This mode can be used to significantly speed up the STEM acquisition. This feature is unique to MerlinEELS detectors.

Effectively noise free

Each of MerlinEELS pixels contains >1100 transistors within the 55 micrometer pitch, enabling intelligent processes to occur on chip. Each incoming electron is evaluated, and if it is above a user specified threshold energy level, the signal is counted. If it is not, then it reads as zero. This unique feature allows for noise-free data collection. This is unique to hybrid pixel technology and strongly differentiates it from analogue integrating detectors, such as indirect CCD technology or CMOS.

Dedicated scan engine

MerlinEELS setup is supplied with a dedicated scan engine supporting advanced scanning options. It allows integration with  additional hardware and is capable of displaying signals from annular and bright field detectors already present on the microscope.

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Talk to our technical sales engineer about your requirements

Dr. Gareth Douglas

Dr. Gareth Douglas

Microscopy Sales Specialist

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