The MerlinEM Direct Electron Detector (DED), a pixelated detector ideal for applications such as 4D STEM and dynamic TEM imaging, offers rapid readout and improved signal to noise.
Scan Engine

MerlinEM is a fast pixelated detector for electron microscopes. MerlinEM’s versatile technology allows for acquisition speeds greater than 21,000 frames per second (@ 1 bit mode) and comes with a workstation computer. MerlinEM is a particle counting detector – each pixel has complex analog and digital circuitry to discriminate single particle events. Noise free, zero dead time readout is possible due to the hybrid design of the detector.

MerlinEM uses threshold discriminators to separate incident electrons from a background signal. It is ideally suited for 4D STEM and dynamical TEM imaging. The detector can be triggered by external events – enabling pump-probe and in situ type of experiments. Near ideal detector performance (in terms of DQE and MTF) can be reached for electron energy decreasing towards 60 keV1.

Key applications

  • 4D STEM.
  • Time resolved TEM.
  • Psychography.
  • Strain imaging.
  • Lorentz microscopy.
  • Electron diffraction imaging.
  • CBED.

Key features

  • Direct detection: Noise-free readout of single electron events.
  • Dynamic range: 24-bit maximum counting depth (1:16.7 million intensity range in a single image), 12-bit counting depth with no dead time.
  • Rapid and versatile readout: Several bit depth modes allow for varying readouts speeds, including up to 1825 Hz in typical 12-bit mode, and up to 21,000 Hz in binary mode (1-bit). Additionally, the shutter speed can be opened for as low as 200 ns for pump-probe experiments.
  • Wide energy range and radiation tolerance:30 keV – 300 keV operating range suitable for low and high energy experiments.
  • Size and Mount: 256 x 256 pixels with retractable and static mounts fits most microscopes.

The Quantum Detectors Scan Engine allows advanced, highly customisable  STEM scanning on electron microscopes.

Key benefits

  • Generate random arbitrary scans using a table of positions as large as 50 Mpixels to  minimise beam damage to  delicate samples.
  • Generate conventional raster scans for STEM imaging or EELS hyperspectral imaging.
  • Acquire up to 6 video channels simultaneously, with the option of 2 of them being used as  external scan inputs.
  • Acquire up to 6 event sources as data channels.
  • Synchronise scan with multiple cameras.
  • Generate a variety of signals to control lasers for pump-probe experiments, detectors etc.
  • Minimum dwell time per pixel: 200 ns.
  • Python / C++ API.

Figure 1: HAADF image and elemental maps of Sc  and Dy in ScDyO3  without drift correction.

Figure 2: HAADF image and elemental maps of Sc and  Dy in ScDyO3  with real-time drift correction. Note   that the Dy-Dy zig-zag chains (shift amplitude 70 pm)  due to the structural distortion of DyScO3  are clearly  visible in both the HAADF and the Dy maps.

Here we report on work by Marcel Tencé et al. on real-time EELS hyperspectral imaging, using the Quantum Detectors Scan  Engine in conjunction with the MerlinEELS direct electron detector, taking advantage of high-speed acquisition and noiseless  readout. This detector enables hyperspectral images to be recorded in sequence while adjusting the scanned area between  each spectrum to remain on the same area of the sample. To achieve this, the group used cross-correlations between successive  HAADF images acquired simultaneously with the EELS hyperspectral images to estimate the drift occurring during each scan.

This approach eliminates the need for a separately defined drift-calculation image as is commonly used at present, but which  often presents difficulties since a suitable region is not always available.

Figure 1 shows an HAADF image and elemental maps of the Sc L edge (ca. 400 eV) and Dy M edge (ca. 1300 eV) signals from  a conventional hyperspectral acquisition without drift correction on an ScDyO3 crystal, oriented along the [100] pseudo-cubic axis. The dwell time was 20 ms, giving a total acquisition time of 444 s. Considerable drift occurred, producing distortions in the  images.

Figure 2 shows the equivalent results using their approach with the Quantum Detectors Scan Engine. Here, 100  hyperspectral acquisitions, each with a nominal pixel dwell time of 200 μs, were collected from the same area and summed. The total signal acquisition time is thus the same as in Figure 1 and the count levels were similar. However, the resulting image and  maps are essentially free of drift distortion. This method is the way forward for EELS hyperspectral imaging.


Technical specifications

Scanengine outputs: 2 Programmable outputs, range ±10 V
Arbitrary scan mode:  Enables Arbitrary Sparse Imaging reducing beam damage to samples
Minimum dwell time per pixel:  200 ns
Video inputs: 6
Synchronisation outputs:  8 TTL
Digital input lines: 5 TTL
Beam blanking control: TTL
Flyback time: µs à ms
Communication : USB 3.0
Operating system: Windows 10
Dimensions : 483mm x 215mm x 88mm

Technical specifications


Sensor : Silicon 500 µm
Sensor type : Reverse-biased silicon hybrid diode array
Pixel size : 55 x 55 µm
Active zone : 14 mm x 14 mm or 28 mm x 28 mm
Pixels : 256 x 256 (single) or 512 x 512 (quadruple)
Playback noise : Zero with defined thresholds
DQE at 60keV : 1 at zero frequency
0.45 at Nyquist1
MTF at 60 keV : >0.62 to Nyquist (mode-dependent)
Max. frame rate (continuous) : 1825 Hz (12-bit)
Gap time (continuous) : 0 µs
Maximum dynamic range : 24 bits - up to 16,777,216 strokes per pixel
Trigger voltage : Impulse 3.3 / 5 V TTL or via integrated software
Communication : Up to 10m VHDCI cable; TCP/IP protocol
Energy range : 30 keV - 300 keV
Software : Labview and TCP/IP protocol
Montage : Static or retractable at the bottom of the column or on a 35 mm port

Quantum Detectors present 4D STEM with MerlinEM

Quantum Detectors live demonstration of the MerlinEM direct electron detector