Helios NanoLab G3 Focused Ion Beam

The Helios is the backbone of our microstructure research. We heavily use it to cut structures from single crystals and to make robust electric contacts to the structures. The dual-beam machine features a both a focused ion beam (FIB) and a scanning electron microscope (SEM). Both ion- and electron-beam can be used to image the sample simultaneously, providing us with three-dimensional perspectives of the structures.

Material deposition – We have a multi gas injection system installed that allows us to deposit material in situ via ion assisted chemical vapor deposition. Metallic layers (Pt) can be grown for electric contact, insulating/semiconducting material (C, TEOS) can be used to electrically isolate parts of the crystals, and superconducting (W, Tc~7K) material can be incorporated into the structure to build quantum coherent devices.
Microcrystallography – The Helios is equipped with an Oxford Instruments electron back-scatter diffraction detector (EBSD). It detects modulation patterns in the angle distribution of the backscattered electrons due to coherent scattering of the SEM beam off a crystalline sample. This enables us to identify the crystal orientation of microcrystals before fabrication, and verify the single-crystalline nature of the final structure.
Compositional analysis – We are interested in exploring the physical properties of novel materials. The often complex chemistry of such new compounds commonly results in off-stoichiometry and unwanted byproducts such as parasitic phases. We can study the detailed composition of micron-sized particles in situ using energy-dispersive X-Ray spectroscopy (EDX).

Raith Electron Beam Lithography

We frequent the newly build clean-room of the institue for nanofabrication using lithography. The RAITH is fully automated and allows wafer-scale processing for substrate manufacture or resist-based lithography steps on crystals of quantum materials. The high resolution mode enables feature sizes below 10nm, that can further be processed in our AXXIS evaporation system, our Ar/O plasma sputtering chamber or for wet chemistry processes.

Sample microfabrication

Many of our sample fabrication processes involve ex-situ manipulation of delicate crystal structures on the micron scale. We have set up a low vibration station for micro-sample manipulation including a hydraulically decoupled, high-precision micromanipulator (sub-micron motion), a high power microscope and a precision soldering station. Here we perform most of our labwork to prepare micro-samples for further processing and measurements.

Superconducting magnets

Magnetic fields tune the ground state of quantum materials in a reversible and non-invasive way. Typical measurements include upper critical fields and vortex dynamics in high temperature superconductors, magnetoresistance in magnetic materials, tuning quantum critical systems in heavy fermion matter, or quantum oscillation experiments. In addition to our high-field work in collaboration with the National High Magnetic Field Laboratory (NHMFL), we operate superconducting laboratory magnets for intermediate to low field projects.

At the moment, we operate the following magnet system:

Johann der Beständige – 8T, 2″ bore. The system will be equipped with a vibration dampened variable temperature insert (1.5K-300K) for low-noise measurements of magnetoresistance and thermodynamic quantities such as the elastic modulus.

August der Starke – 16T, 1″ bore (exp. April 2016). Our flagship magnet will be equipped with straight probe sticks for high-frequency measurements, a high-precision rotator, and a Helium-3 insert to extend our temperature range to 280mK.