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ETH Zrich - D-PHYS - Solid State Physics - Microstructure Research - Instrumentation - SKEM

SKEM

Selected Article

Nat. Comm 7, 13611 (2016)
Critical exponents and scaling invariance in the absence of a critical point
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Proc. R. Soc. A 472, 2195 (2016)
Thirty per cent contrast in secondary-electron imaging by scanning field-emission microscopy
>>
Phys. Rev. B 89, 014429 (2014)
Domain-wall free energy in Heisenberg ferromagnets
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Phys. Rev. B 87, 115436 (2013)
Scale invariance of a diodelike tunnel junction
>>
Scanning Kerr Microscopy (SKEM)
A magnetic map of the surface magnetization of a sample is obtained by Kerr effect using a focused laser beam as source and by scanning the sample. The sample is scanned using a home built high precision mechanical XY micropositioner driven by DC motors.

A reproducible step size is crucial for collecting Kerr effect images. Best results were achieved by using commercially available linear rails equipped with titanium nitride balls as bearings for the XY stage. The reproduceability is in the order of one micrometer. The sample is mounted with the surface pointing along the z axis (vertical axis of the system). Additional rotation of the sample around the z axis is possible. For measuring the Kerr rotation, the light from a stabilized laser diode ( l = 675 nm) is directed through a linear polarizer (extinction better than 10-6) and the focussing optics onto the sample. The optics is located in the tube of a reentrant UHV view port. Optics and view port were specially designed in order to reach a diffraction limited laser focus. The Kerr signal arising from the surface magnetization is measured by using a method described elsewhere. An external magnetic field up to 0.1 T can be applied along the sample surface perpendicular to the plane of incidence.The spatial resolution of the apparatus is given by the size of the laser focus and can be estimated from the sharpness of the boundary between magnetic and non magnetic areas. The current set up has a lateral resolution of 1.3 um. Notice that Secondary Electron Microscopy with Polarization Analysis (SEMPA) has a better spatial resolution (typically 20 nm). However, this technique does not generally allow measurements in an applied external magnetic field.
The SKEM apparatus features three independently pumped ultra high vacuum chambers and a fast entry load lock:

Preparation chamber (right), SKEM chamber (middle) and STM chamber (left) are connected with gate valves. Sample manipulation is done with magnetically coupled wobblestick manipulators.

Normal base pressures are in the range of 4*10-11mbar to 1*10-10mbar. For vibration isolation, the whole system is suspended on pneumatic dampers. During experiments, the vacuum is maintained by ion gettering pumps and TSP's only. All mechanical pumps can be swiched off.
The SKEM system is equipped with a variety of sample preparation and characterisation tools:
Auger analyser (RFA) for chemical characterisation of the sample surface

Low energy electron diffraction Optics (LEED) for structural characterisation

Ion sputtering gun

High temperature heating stage (2500C)

Evaporators for epitaxial growth of metal thin films

Evaporation stage with a special arrangement of apertures for growing laterally structured thin films.

Scanning tunneling microscope with three axis positioning
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