The electron source used in the Merlin is a thermal field-emission cathode, known as a Schottky emitter (ZrO / W cathode). Due to the filament voltage (Fil I), ZrO diffuses toward the cathode tip, reducing the work function of the electrons from 4.6 eV to 2.8 eV. Depending on the cathode temperature and the field strength measured at the cathode tip—generated by the emitter electrode potential—an equilibrium is established that stabilizes the work function of the field-emission cathode.
Resolution (Measurements taken on a Plano S1969 gold-on-carbon sample with a scan speed of 3 and 60-fold line averaging) | 1.0 nm at 15 kV at the optimal working distance 2.1 nm at 1 kV at the optimal working distance 3.0 nm at 0.2 kV at the optimal working distance 3.0 nm at 20 kV and 10 nA at a working distance (WD) of 8.5 mm |
Acceleration voltage | 0.02 kV to 30 kV |
Probe current | 10 pA to 300 nA |
Magnification | x12 to x2,000,000 compared to a Polaroid reference |
Working Distance | from 1.5 mm to 50 mm |
Room Dimensions | inner diameter 330 mm height 270 mm |
Platinum Race | X/Y = 130 mm Z = 50 mm T = -3° to +70° continuous 360° rotation |
Maximum sample weight | 500 g |
The Merlin has three imaging sensors:
| Inlens | SE2 | AsB |
Electron type | High Schools | High Schools | Re-broadcasts |
Special Features | Low-magnification shadows (<200); Significant surface carbon pollution | Suitable for low magnification; Not suitable for low WD values; | Includes a gain adjustment in addition to brightness and contrast; Often requires a higher current and/or a lower scanning speed than the other two |
The Merlin is equipped with an EDX (Energy-Dispersive X-ray Spectrometer) detector with the following specifications:
Silicon Drift crystal with a nominal active surface area of 50 mm²;
SATW Light Element Window for the detection of elements from beryllium through uranium.
The Merlin is equipped with a WDX spectrometer (Wavelength Dispersive X-ray Spectrometer) that uses standards to quantify the elements present in the sample, particularly light elements or those at very low concentrations (<1%). This spectrometer features a 6-crystal rotator, covering a wide range of wavelengths from 0.07 keV to 10.84 keV.
The Merlin enables EBSD acquisitions using its Nordlys II S camera, also from Oxford Instruments. It is located to the right of the microscope chamber. This camera features front-mounted detectors for imaging, known as FSDs ( ForeScatter Detectors). These detectors reveal the grain and subgrain structure of the tilted sample.
The Merlin SEM can also be equipped with a heated microtensile stage to observe microstructures in real time during mechanical testing of samples.
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